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Titration Applications Brochure 22

Surfactant Titration

for METTLER TOLEDOTitrators DL50/DL53/DL55/DL58

OSO3- Na+

Hydrophobic group Hydrophilic group

Water

Micelle

/68 DL50 DL53 DL55 DL58 METTLER TOLEDO Titrators Surfactant Titration

Editorial

Dear Reader

Surfactants and detergents are an integral part of our daily life. Be it cleaning, dishwashing or personalhygiene, we all have a great deal of contact with these substances. Analysis of surfactant concentrationis an important quality criterion in production.

It is with pleasure that we present to you this unique and comprehensive application brochure, whichprovides essential information on different analytical techniques used for surfactant analysis.

Our thanks go to Cosimo De Caro, an experienced applications chemist, who put in tremendous effortsin the development of this brochure.

We wish you a lot of success in surfactant titration !

Christian Walter Rolf M. RohnerManager Market Support AnaChem Marketing Manager Titration

Surfactant Titration DL50 DL53 DL55 DL58 METTLER TOLEDO Titrators /68

Contents

Introduction ......................................................................................................................................... 4

Turbidimetric titrations ........................................................................................................................ 9M603 Turbidimetric titration: Determination of anionic surfactants ............................................... 10M604 Turbidimetric titration of a cocoamidopropylbetaine solution .............................................. 14M605 Turbidimetric titration of nonionic surfactants ...................................................................... 16

Colorimetric Two-Phase Titrations .................................................................................................... 20M606 Standardization of Hyamine by Two-Phase Titration (DL58) ............................................... 22M607 Determination of anionic surfactants by Two-Phase Titration (DL58) .................................. 24M073 Two-Phase Titration with DL77: Standardization of Hyamine 1622..................................... 28M074 Two-Phase Titration with DL77: Anionic surfactants determination .................................... 31M608 Mixed Two-Phase Titration: Standardization of Hyamine 1622............................................ 35M609 Mixed Two-Phase Titration: Anionic surfactants in liquid detergents ................................... 37

Potentiometric titrations .................................................................................................................... 40M610 Titer of Hyamine 0.004 mol/L by potentiometric titration .................................................... 41M611 Titer of SDS 0.004 mol/L by potentiometric titration ............................................................ 43M612 Titer of sodium tetraphenylborate by potentiometric titration ............................................... 45M613 Potentiometric titration of anionic surfactants in liquid detergents ....................................... 47M614 Potentiometric titration of nonionic surfactants in raw materials .......................................... 50M615 Potentiometric titration of a betaine in shampoo ................................................................... 54

M081 Anionic components in water soluble metal working fluids .................................................. 56

Surfactant titration: Comparison of different techniques .................................................................. 60

Conclusions ....................................................................................................................................... 63

Checklist for surfactant titration ........................................................................................................ 64

Literature ........................................................................................................................................... 67


Introduction

Surfactants is the generic name for substances with a surface active behaviour. They have a characteristicstructure with one or more hydrophobic (no affinity to water) and one or more hydrophilic groups(strong affinity to water) [see literature ref. 1-5]

Fig. 1:

Hydrophobic group Hydrophilic group

In aqueous solutions, the hydrophilic groups of the surfactant molecules are in contact with water,whereas the hydrophobic groups attempt to avoid water by emerging from the solution. Thereby theyform a monomolecular layer that covers the surface of the solution (see fig. 2).

Surface tension results from interaction of neighbouring molecules forming the layer. Since theinteraction between a surfactant and a water molecule is weaker than that between two water molecules,the surface tension of a surfactant solution is considerably reduced compared to water.

When a specific concentration is reached and the surface of a solution is completely covered, additio-nal surfactant molecules form spheric aggregates: micelles. This concentration is called the criticalmicelle concentration (cmc). In a micelle, the hydrophilic groups build the surface of the sphere andthe hydrophobic tails are oriented towards the center of the micelle. The hydrophobic center allowsthe inclusion of nonpolar molecules (Fig. 2).

Water

Micelle

Sodium palmitinate: C15

H31

COONa

Sodium stearate: C17

H35

COONa

Sodium laurinate: C11

H23

COOH

COO- Na+

For this reason, surfactants increase the dissolving power of water for organic nonpolar substances(e.g. fat) and are therefore used as detergents in many applications. Soaps, i.e. the sodium (Na+) orpotassium (K+) salts of fatty acids, are well-known examples of surfactants:

Fig. 2:


1. Anionic Surfactants (negative charge)

Alkyl sulphate

Sodium lauryl sulphate

(Sodium dodecyl sulphate, SDS)

Linear alkylbenzene sulphonate (LAS)

Alkylbenzene sulphonate (ABS)

Alkyl ether sulphate CH3(CH

2)

10CH

2O(CH

2CH

2O)

4SO

3- Na+

Sodium n-dodecyltetraethoxysulphate

(Sodium laureth sulphate)

2. Cationic Surfactants (positive charge)

Alkyl pyridinium salts

n-Cetylpyridinium chloride (CPC, M = 340 g/mol)

usually available as CPC monohydrate, M = 358.01 g/mol

Quaternary ammonium salts Benzethonium chloride

(Hyamine 1622, M = 448.10 g/mol)

Imidazolium salts DDMICl

(1,3-didecyl-2-methyl-imidazolium chloride, M = 399.10 g/mol)

Fatty quaternary ammonium salts C16

H33

N+

Types of surfactantsSurfactants are classified according to the type and charge of the hydrophilic groups present in themolecule. We distinguish four different classes: anionic-, cationic-, nonionic- and amphoteric surfactants.

Among these surfactants, anionic surfactants (including soap) are the most important, with a worldwidemarket share of 55% (1991), followed by the nonionic (39%), cationic (4%) and amphoteric detergents(2%). The advantage of nonionic surfactants is their high solubility at low temperature, which is idealfor laundry temperatures of about 30 °C. Among nonionic surfactants, sugar-based alkylpolyglucosides(APG) have to be mentioned since they are becoming more relevant these days.

N+Cl-

OSO3- Na+

SO3- Na+

SO3- Na+

Cl-


3. Nonionic Surfactants (no electric charge)

Ethoxylated alkylphenols CH3 CH

CH

2CH CH

2 CH O(CH

2CH

2O)

9H

CH3

CH3

CH3

Nonylphenol 9-mole ethoxylate

Alkyl polyethyleneglycols CH3(CH

2)

10CH

2O(CH

2CH

2O)

9H

Dodecanol 9-mole ethoxylate ( 1 EO unit: -CH2CH2O- )

4. Amphoteric Surfactants CH3

Alkylbetaines C12

H25

N+ CH2COO-

CH3

Dimethyl-dodecyl-betaine (Carboxybetaine)

Amidobetaines CXH

2X+1 CO NH (CH

2)

2 N+ CH

2COO-

Alkyl ammonium sulphonatesCH

3

N-Decyl-N,N-dimethyl-3-ammonium-1-propane sulphonate

Usually, surfactant molecules have not a single specific alkyl chain (e.g., C12

), but they are characterizedby a distribution of alkyl chains of various lengths. For instance, betaines contained in commercialproducts such as shower foams and shampoos contain alkyl chains which can vary between C

8 and

C18 [4].

In ethoxylated alkylphenols the number of EO-units (i.e., -CH2-CH

2-O- ) can also vary e.g. between 7

and 9. Thus, the indicated molecular mass M of a surfactant has usually to be understood as a weightedaverage value of the molecular masses of the components with various alkyl chains.

CH3

CH3

N+ SO3-

CH3

CH3


Surfactants in finished products and formulations

The typical composition of formulated products, of which the analyses are documented in this brochure,is given below. Cationic surfactants are used seldomly and were not amongst the analysed products.

Product Composition

Anionic Nonionic Cationic Amphoteric OtherComponents

Shower foam ✓ (✓) ✓ Water > 40-50%Additional components 1)

Liquid detergents ✓ (✓) ✓ Water > 40-50%Additional components 2)

Liquid dishwasher ✓ ✓ Water > 40-50%Additional components 3)

Washing powder ✓ ✓ WaterFatty acidsAdditional components 4)

Toothpaste (Gel) ✓ Water < 20%Additional components 5)

1) small percentages: perfumes, dyes, stabilizers, cellulose derivatives and salt (viscosity), alcohol.2) small percentages: perfumes, dyes, stabilizers, salt (viscosity), alcohol.3) small percentages: perfumes, dyes, skin protective substances.4) small percentages: perfumes, enzymes, builders, borates, silicates, phosphates, carbonates.5) small percentages: amine fluorides, polyglucosides, silica, titanium dioxide, phosphates, cellulose, fluorine.

This table has to be considered as an indicative table. Detailed information can be found in references[1] and [4]. Note that each product has its specific formulation, and the composition includes morethan one class of surfactants and additional substances (salts, fragrances, ...). These componentsgenerally affect the analysis and interferences can not be excluded. Thus, appropriate choice of pHand sample preparation, e.g., separation of the components or chemical modifications, can be necessary[see ref. 1, 2, 3, 4, 5]. For instance, too low a pH can lead to protonation of betaines (carboxylic group,-COO - ... H+). The protonated betaines can partially neutralize the anionic analyte in the sampleleading to a lower result [see ref. 4].


Overview of the titration techniques

Turbidimetric TitrationThe turbidity of an aqueous or mixed phase sample solution is measured using a phototrode. Thissensor measures the light transmission through the sample. Near the equivalence point, a precipitatebetween titrant and analyte is formed, and the solution becomes turbid. The equivalence point is at theminimum in light transmission (Evaluation: «Minimum»). However, if the signal does not show aclear minimum and is noisy, the curve is evaluated at the largest change in turbidity (Evaluation:«Standard»). In this case, the curve obtained from the standardization of the titrant must also beevaluated with the standard evaluation.

Two-Phase TitrationTo determine the anionic (cationic) surfactant content in a water/chloroform two-phase medium [seeref. 1, 2, 3], the colour change of a mixed indicator is monitored with a phototrode [6]. The analyte istitrated with a counter ionic surfactant, e.g. anionic surfactants are titrated with cationic surfactants(Hyamine 1622, CPC or DDMICl). An anionic-cationic non-polar complex is formed which is thenextracted into the organic phase (chloroform). After each increment addition, the mixture is stirredvigorously and then allowed to separate. This particular sequence can be achieved either with thefunction «Two-phase titration» of the DL58 titrator or by synchronization of Analyses A and B of theDL77 titrator. An additional possibility is to skip the separation of the two liquid phases by measuringunder continuous stirring of the sample (Mixed two-phase titration).The light transmission is usually measured in the organic phase. At the equivalence point, the colourof the organic phase changes from pink (blue) to blue (pink) leading to a sudden change in lighttransmission. The curve is evaluated at the largest change in transmission (Evaluation: «Standard»).

Potentiometric TitrationPotentiometric titrations are indicated with a surfactant sensitive electrode (SSE). Generally, a SSEhas a PVC membrane or consists of a graphite rod containing an ion carrier [see ref. 1, 3, 4, 5]. Thepotential is formed by interaction between the ion carrier and the analyte in the sample solution. It ismeasured against a reference electrode. During titration, the surfactant forms a non-polar complexwhich leads to a potential change. Potentiometric surfactant determinations give S-shaped titrationcurves which can be evaluated with the «Standard» evaluation procedure.

Titration with the DN100 Infratrode photometric sensorA DN100 sensor dipping into the titration beaker can indicate turbidity changes, refractive indexchanges or both effects. This sensor has been developed especially for anionic content determinationin cooling lubricants and metal working fluids. Since these sample are usually milky when dilutedwith water, the determination is hardly possible with the phototrode.

CommentsAll techniques are based on the formation of a non-polar complex between analyte and titrant whichprecipitates in the solution. To achieve correct results, following parameters must be taken into account:

• Reaction speed: How long does it take to form the precipitate?The signal acquisition must consider the kinetics of the precipitation reaction: Select theappropriate parameters of the «Measure mode» ( i.e., t(min), t(max) ,...).

• Solubility and stability of the formed complex:The precipitation must be complete and the complex must be insoluble.


Turbidimetric titrationsPrincipleAnionic (cationic) surfactants are titrated with cationic (anionic) surfactants. Near the equivalencepoint, a colloidal precipitate is formed, and the solution becomes turbid. In most cases, the precipitatedissolves again, due to titrant excess, and the turbidity disappears.

Shape of CurvesAt the equivalence point, maximum turbidity is reachedand a minimum in light transmission is measured witha phototrode. In most cases, the curves obtained havea well-defined minimum: the curve can be evaluatedaccording to the «Minimum» procedure.

However, some applications are also evaluated for thelargest change in turbidity (Evaluation «Standard»),since the curves do not show a clear minimum. In thiscase, the titer determination must be performed withthe «Standard» procedure.

Tips & Hints

1. pH value of the sampleThe pH value of the sample solution affects the results. Depending on sample composition, theappropriate pH value has to be chosen to titrate the desired component.Example: detergent containing anionic surfactants and fatty acid.• Titration of sample at pH 3: anionic surfactants.

Interferences due to fatty acids and amphoteric surfactants are avoided.• Titration of sample at pH 10: anionic surfactants and fatty acids.

2. Evaluation procedureTo select the appropriate evaluation, a titration can be performed without termination after theequivalence point. From the shape of the whole curve the appropriate evaluation can be chosen.

3. Stirring• Avoid foaming of the sample: medium to slow stirring speed.• Appropriate dilution of the sample to avoid formation of a vortex and air bubbles.• Stirring prevents adhering of bubbles to the window or to the mirror of the phototrode.

4. Cleaning and conditioning• During titration a precipitate is formed which covers a) the mirror of the phototrode, and b) the

stirrer. Therefore, clean the phototrode thoroughly after each sample with water or, if necessary,with ethanol.

• When using a sample changer, introduce a conditioning step for cleaning after each sample.

Titer detemination of Hyamine with SDS

Titer detemination of SDS with CPC


METTLER TOLEDO Application No. M603

Turbidimetric titration: Determination of anionic surfactants

Instruments: METTLER TOLEDO DL58METTLER TOLEDO AT261Printer

Method: 80042

Accessories: Titration beaker ME-101974

Indication: DP550 with DIN-LEMOadapter cable ME-89600

Sample: Liquid detergents (5 g in 500 mL)10 mL aliquot

Compound: Anionic surfactants

Preparation: 50 mL deion. water

Titrant: Hyaminec(Hyamine) = 0.01 mol/L

Standard: Sodium dodecylsulphate (SDS)10 mL 0.01 mol/L aliquot

Results: METTLER TOLEDO DL58 Titrator V2.0 Mettler-Toledo GmbH Team OST: ms/dr Market Support Laboratory

Method 80042 Tenside/Anionics/DP550 01-Apr-1997 20:08 Measured 01-Apr-1997 20:28 User dr

ALL RESULTS

No. ID Sample size and results

1 Spülm. 1 5.0621 g R1 = 4.6145 mL Vbr. TM R2 = 17.238 % AT mittl. M.=387 2 Spülm. 1 5.0621 g R1 = 4.6085 mL Vbr. TM R2 = 17.216 % AT mittl. M.=387 3 Spülm. 1 5.0621 g R1 = 4.6152 mL Vbr. TM R2 = 17.241 % AT mittl. M.=387 4 Spülm. 1 5.0621 g R1 = 4.6198 mL Vbr. TM R2 = 17.258 % AT mittl. M.=387 5 Spülm. 1 5.0621 g R1 = 4.6135 mL Vbr. TM R2 = 17.234 % AT mittl. M.=387

STATISTICS Number results R2 n = 5 Mean value x = 17.237 % AT mittl. M.=387 Standard deviation s = 0.01512 % AT mittl. M.=387 Rel. standard deviation srel = 0.088 %


Comments on method

• In this application the total content of washingactive matter is determined. According to theproducer, the average molar mass used for thecalculation of the total washing active matter is387. The sample contains fatty alcohol ethersulphate and secondary alkyl sulphonate asanionic surfactants, as well as cocoamidopropylbetaine (amphoteric surfactant).The sum of these components is defined as totalwashing active matter. Classical two-phase (2P)titration is the standard method performed by theproducer. As a reference, the value of 17.1 % isobtained with 2P-titration (see page 61).The pH has to be adjusted to avoid interferencesdue to other surfactants present in the sample. Inthis case, it was not necessary to adjust the pHsince the results obtained show an excellentagreement with the reference value of 17.1% (seecomparison on page 62).

• Formation of air bubbles during titration has tobe avoided since they disturb the photometricindication. After each titration the phototrode isrinsed with water.

• The transmission change at the equivalence pointis usually sharp. Problems arising from smallirregularities of the titration curve, from airbubbles or other sources can be avoided by settingan appropriate threshold value.

• The amount of surfactant before dilution (5 g) isgiven as sample size. The dilution is taken intoaccount with (m*10/500) in the calculation.

• A sample changer ST20A can be used for a fullyautomatic analysis procedure. The method can beeasily modified: Enter «ST20A» as titration standin the function «Sample».

Waste disposal

Special treatment is not necessary.

Author: D. Rehwald, Ch. Walter, C. De Caro

Method 80042 Tenside/Anionics/DP550 Version 01-Apr-1997 20:08

Title Method ID . . . . . . . . . . . . . 80042 Title . . . . . . . . . . . . . . . Tenside/Anionics/DP550 Date/time . . . . . . . . . . . . . 01-Apr-1997 20:08 Sample Sample ID . . . . . . . . . . . . . Spülm. 1 Entry type . . . . . . . . . . . . . Weight Lower limit [g] . . . . . . . . . 4.0 Upper limit [g] . . . . . . . . . 6.0 Molar mass M . . . . . . . . . . . . 387 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . Stand 1 Temperature sensor . . . . . . . . . TEMP A Stir Speed [%] . . . . . . . . . . . . . 40 Time [s] . . . . . . . . . . . . . . 10 EQP titration Titrant/Sensor Titrant . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . 0.01 Sensor . . . . . . . . . . . . . DP550 Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . to volume Volume [mL] . . . . . . . . . . . 3 Wait time [s] . . . . . . . . . . 20 Titrant addition . . . . . . . . . . Incremental ∆V [mL] . . . . . . . . . . . . . 0.1 Measure mode . . . . . . . . . . . . Timed increment ∆t [s] . . . . . . . . . . . . . 4.0 Recognition Threshold . . . . . . . . . . . . 500.0 Steepest jump only . . . . . . . No Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Negative Termination at maximum volume [mL] . . . . . 10.0 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . Yes n = . . . . . . . . . . . . . 1 comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition = . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=VEQ Constant . . . . . . . . . . . . . . Decimal places . . . . . . . . . . . 4 Result unit . . . . . . . . . . . . mL Result name . . . . . . . . . . . . Vbr. TM Statistics . . . . . . . . . . . . . No Calculation Formula . . . . . . . . . . . . . . R2=(Q*C2)/(m*10/500) Constant . . . . . . . . . . . . . . C2=M/(10*z) Decimal places . . . . . . . . . . . 3 Result unit . . . . . . . . . . . . % AT Result name . . . . . . . . . . . . mittl. M.=387 Statistics . . . . . . . . . . . . . Yes Report Output unit . . . . . . . . . . . . Printer Results . . . . . . . . . . . . . . Yes All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . Yes Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - V curve . . . . . . . . . . No ∆

2E/ ∆V

2 - V curve . . . . . . . . . No

log ∆E/ ∆V - V curve . . . . . . . . No E - t curve . . . . . . . . . . . . No V - t curve . . . . . . . . . . . . No ∆V/ ∆t - t curve . . . . . . . . . . No

Other titrators

Method 80042 also runs with the followingtitrators:DL50, DL53, DL55DL67, DL70ES, DL77

Method

E – V curve


ResultsProduct Nominal Reference Number of Content RSD RemarksSurfactant component value, % value, % samples % %

(Tot. Active matter)

Liquid detergent 1 18.0 17.1 5 17.24 0.09 no pH adjustment

Average molar mass: 387 pH 3 (n)Fatty alcohol ether sulphate 10.0Secondary alkanesulphonate 6.0Cocoamidopropylbetaine 2.0

Conc. liquid detergent 2 38.5 32.8 5 34.49 0.02 no pH adjustment

Average molar mass: 362 pH 3 (n)Fatty alcohol ether sulphate 11.0Secondary alkanesulphonate 20.0Cocoamidopropylbetaine 3.5Nonionic surfactant (7 EO, M=520) 4.0

Liquid detergent 3 33.0 - 7 34.44 0.07 m= 15 gr/500 mL

Average M = 353.09 (n) INC=0.1 mL

Anionic surfactant A (M=346) 27.0 EQU:

Anionic surfactant B (M=385) 6.0 0.5/1 mV/s, 3-20 sthreshold=500

Liquid detergent 4Anionic surfactant as SDS Lit: 15-30 14.18 5 14.32 1.56 INC=0.15 mL

(M=288.38) pH 1-2 (n) EQU:

0.5/1 mV/s, 6-30 s,c(CPC)=0.01 M

Liquid dishwasher Lit: 15-30 10-15 5 11.22 0.18 m=0.05 gr. /sample

Anionic surfactant as SDS (n) c(Hya)=0.004 M

(M=288.38) DYN: 10 mVEQU: 1/5 mV/s,

3-20 s, thresh.: 500

Shower foam 1 15.0 - 7 15.01 0.63 m=0.05 gr. /sample

Na-Laurylether sulphate (M=430) 13.0 (n) c(Hya)=0.004 M

Betaine (M=390) 2.0 INC: 0.15 mL ,EQU: 1/2 mV/s,6-30 s, thresh.: 300

Na-Laurylether sulphate 71.0 - 7 76.85 0.23 m=0.005 g/sample

Raw material, M=432 (n) c(Hya)=0.004 MINC: 0.1 mL ,EQU:1/2 mV/s, 6-30s,thresh.: 600

Washing powder 1 - - 6 7.28 2.22 m=0.10 g/sample

Anionic surfactant as SDS (n) INC: 0.075 mL ,(M=288.38) EQU: 0.1/2 mV/s,

3-10 s, thresh.: 10


Product Theoretical Reference Number of Content RSD RemarksSurfactant component content, % value, % samples % %

(Tot. Active matter)

Washing powder 4Na-DBS (M=348.49) 3-5 - 5 3.49 2.43 pH 3

only NaDBS

Fatty acids, FA (M=274) 4-6 - 5 3.56 4.53 pH 10Na-DBS+ FA

Nonionic surfactant (M=740) 2-4 -

Shampoo 1 - - 5 19.88 0.60 m=0.004 g/sample

Anionic surfactant as SDS (M=288.38) (n) c(Hya)=0.004 M

Nonionic surfactant 2-6 INC: 0.1 mL ,TFIX: 5 s,threshold: 500

Nominal value: Theoretical composition of the sample as total washing active matter. It is obtained bysumming the percentages of all surfactant components in the sample.

Reference: Value given by the producer and mostly based on classical two-phase titration. It indicatesthe total washing active matter determined at a defined pH.

(n): Sample dissolved in water without pH adjustment.

General remarks

• Various samples with different surfactantcompositions have been measured. Their methodswere developed from method 80042. Parameterchanges with respect to method 80042 are givenunder «Remarks».

• Washing powders result in a turbid sample evenwith a low sample size. The transmission is verylow and therefore the appropriate threshold andsample size must be selected.

• Washing powder 4:In this case, a single method has been developedfor the titration of both components, i.e., anionicsurfactants (Na-DBS) and fatty acids (FA).3 g of the powder were dissolved in warm waterand then diluted to 500 mL. 20 mL aliquots weretitrated. Structure of the method:1. Adjust pH value to pH 32. Titration of Na-DBS with Hyamine3. EP-Titration to pH 10.4.Titration of FFA and Na-DBS with Hyamine.

Comment:The inverse titration, i.e., first at pH 10 and thenat pH 3 did not lead to correct results.

Table of measured values

(liquid detergent 3)

Volume Increment Signal Change 1st deriv. Time

mL mL mV mV mV/mL min:s

ET1 0.0000 1057.1 0:03 1.1420 1.1420 1006.5 -50.7 -44.4 0:19 1.7130 0.5710 947.6 -58.9 -103.1 0:31 ET2 2.0000 0.2870 908.8 -38.8 -135.1 0:47 2.1000 0.1000 892.0 -16.6 -166.1 0:53 2.2000 0.1000 873.7 -18.5 -184.8 0:59 2.3000 0.1000 854.5 -19.3 -192.6 1:06 2.4000 0.1000 836.8 -17.7 -177.1 1:12 2.5000 0.1000 821.4 -15.4 -153.8 1:18 2.6000 0.1000 800.8 -20.5 -205.5 1:26 2.7000 0.1000 780.2 -20.6 -206.1 1:33 2.8000 0.1000 761.0 -19.3 -192.6 1:42 2.9000 0.1000 742.0 -19.0 -190.0 1:52 3.0000 0.1000 720.1 -21.8 -218.4 1:59 3.1000 0.1000 699.8 -20.4 -203.6 2:17 3.2000 0.1000 662.0 -37.7 -377.4 2:21 3.3000 0.1000 631.5 -30.6 -305.7 2:36 3.4000 0.1000 589.0 -42.5 -424.6 2:41 3.5000 0.1000 563.6 -25.5 -254.6 2:57 3.6000 0.1000 536.8 -26.8 -267.5 3:05 3.7000 0.1000 513.3 -23.5 -235.2 3:17 3.8000 0.1000 485.4 -27.9 -278.5 3:27 3.9000 0.1000 444.8 -40.6 -406.5 3:39 4.0000 0.1000 391.3 -53.4 -534.4 3:44 4.1000 0.1000 312.5 -78.8 -788.4 4:03 EQP1 4.2000 0.1000 218.5 -94.0 -940.2 4:23 4.3000 0.1000 132.6 -85.9 -858.8 4:44 4.4000 0.1000 66.4 -66.2 -661.7 5:05



Turbidimetric titration of a cocoamidopropylbetaine solution

Instruments: METTLER TOLEDO DL58METTLER TOLEDO AT261HP550 Printer

Method: Bet

Accessories: Titration beaker ME-101974Peristaltic pump ME-65241

Indication: DP550 with DIN-LEMO adaptercable ME-89600

Sample: 3 mL aliquot(5.0017 g of a 30% solution in500 mL)

Compound: CocoamidopropylbetaineAverage M = 350; z = 1

Preparation: - 5 mL 0.1 mol/L HCl- 5 mL PVA solution- 40 mL deion. water

Titrant: Sodium tetraphenylboratec(NaTPB) = 0.004 mol/Ladjust the pH to 9-10

Standard: Silver nitrate (pH-buffer: 4.75)

METTLER TOLEDO DL58 Titrator V2.0 Mettler-Toledo GmbH 004 Market Support Laboratory

Method Bet Betain content 27-Jun-1997 13:33 Measured 27-Jun-1997 14:52 User J. Maag

ALL RESULTS


1 Betain F 3.0 mL R1 = 5.867 mL Consumption R2 = 2.738 mg/mL Betain F Con. R3 = 91.236 % recovery 2 Betain F 3.0 mL R1 = 5.926 mL Consumption R2 = 2.766 mg/mL Betain F Con. R3 = 92.169 % recovery 3 Betain F 3.0 mL R1 = 5.846 mL Consumption R2 = 2.728 mg/mL Betain F Con. R3 = 90.903 % recovery 4 Betain F 3.0 mL R1 = 5.893 mL Consumption R2 = 2.750 mg/mL Betain F Con. R3 = 91.636 % recovery 5 Betain F 3.0 mL R1 = 5.912 mL Consumption R2 = 2.759 mg/mL Betain F Con. R3 = 91.936 % recovery 6 Betain F 3.0 mL R1 = 5.919 mL Consumption R2 = 2.762 mg/mL Betain F Con. R3 = 92.034 % recovery

STATISTICS Number results R2 n = 6 Mean value x = 2.750 mg/mL Betain F Con. Standard deviation s = 0.01474 mg/mL Betain F Con. Rel. standard deviation srel = 0.536 %

STATISTICS Number results R3 n = 6 Mean value x = 91.682 mg/mL Betain F Con. Standard deviation s = 0.49139 mg/mL Betain F Con. Rel. standard deviation srel = 0.536 %

Results:


Method Comments on Method

• According to the producer, the concentration isabout 30% (see calculation R3). Stock solution:5.0017 g of a 30% betaine solution are dilutedwith water in a 500 mL flask.

• The recovery shows an average value of 91%.This is most probably due to incompleteprecipitation. Cocoamidopropylbetaine has adistribution of different alkyl chain lengths, andchains shorter than C

8 are hardly precipitated.

Therefore, a calibration factor is needed whensamples are measured.

• Polyvinyl alcohol (PVA) solution:Dissolve 3-4 g PVA in ca. 250 mL warm water,and allow the solution to cool down beforeaddition (PVA, e.g. from Merck, No. 114266, orFluka, No. 81366).

• If no transmission minimum can be found, e.g.the transmission signal does not increase again,use the evaluation procedure «Standard» andevaluate the titration curve obtained from the titerdetermination with the same procedure.

Waste disposalNeutralization of the titrated sample.

Author: J. Maag

E – V curve

Method Bet Betain content Version 27-Jun-1997 13:33

Title Method ID . . . . . . . . . . . . . Bet Title . . . . . . . . . . . . . . . Betain content Date/time . . . . . . . . . . . . . 27-Jun-1997 13:33 Sample Sample ID . . . . . . . . . . . . . Betain F Entry type . . . . . . . . . . . . . Fixed volume Volume [mL] . . . . . . . . . . . 3.0 Molar mass M . . . . . . . . . . . . 350 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . ST20A Pump . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 50.0 Stir . . . . . . . . . . . . . No Pump . . . . . . . . . . . . . . No Rinse . . . . . . . . . . . . . . No Conditioning . . . . . . . . . . Yes Time [s] . . . . . . . . . . . 20 Interval . . . . . . . . . . . 1 Rinse . . . . . . . . . . . . No Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 20 Time [s] . . . . . . . . . . . . . . 30 EQP titration Titrant/Sensor Titrant . . . . . . . . . . . . . NaTPB Concentration [mol/L] . . . . . . 0.004 Sensor . . . . . . . . . . . . . DP550 Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . No Titrant addition . . . . . . . . . . Incremental ∆V [mL] . . . . . . . . . . . . . 0.05 Measure mode . . . . . . . . . . . . Timed increment ∆t [s] . . . . . . . . . . . . . 5.0 Recognition Threshold . . . . . . . . . . . . 150.0 Steepest jump only . . . . . . . No Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . None Termination at maximum volume [mL] . . . . . 7.0 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . No comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Minimum Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition = . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=VEQ Constant . . . . . . . . . . . . . . Decimal places . . . . . . . . . . . 3 Result unit . . . . . . . . . . . . mL Result name . . . . . . . . . . . . Consumption Statistics . . . . . . . . . . . . . No Calculation Formula . . . . . . . . . . . . . . R2=Q*M/m Constant . . . . . . . . . . . . . . Decimal places . . . . . . . . . . . 3 Result unit . . . . . . . . . . . . mg/mL Result name . . . . . . . . . . . . Betain F Con. Statistics . . . . . . . . . . . . . Yes Calculation Formula . . . . . . . . . . . . . . R3=R2*100/3.001 Constant . . . . . . . . . . . . . . Decimal places . . . . . . . . . . . 3 Result unit . . . . . . . . . . . . % Result name . . . . . . . . . . . . recovery Statistics . . . . . . . . . . . . . Yes Report Output unit . . . . . . . . . . . . Printer Results . . . . . . . . . . . . . . No All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . Yes Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - V curve . . . . . . . . . . No ∆

2E/ ∆V

2 - V curve . . . . . . . . . No

log ∆E/ ∆V - V curve . . . . . . . . No E - t curve . . . . . . . . . . . . No V - t curve . . . . . . . . . . . . No

∆V/ ∆t - t curve . . . . . . . . . . No

Table of measured values Volume Increment Signal Change 1st deriv. Time


ET1 0.0000 887.9 0:05 0.0500 0.0500 886.6 -1.3 -25.8 0:10 0.1000 0.0500 885.9 -0.6 -12.9 0:15 0.1500 0.0500 886.1 0.1 2.6 0:20 0.2000 0.0500 884.1 -1.9 -38.8 0:25 0.2500 0.0500 881.6 -2.5 -50.4 0:30

5.7500 0.0500 15.3 -1.4 -28.4 9:40 5.8000 0.0500 15.3 0.0 0.0 9:45 EQP1 5.8500 0.0500 14.7 -0.6 -11.6 9:50 5.9000 0.0500 14.8 0.1 1.3 9:55 5.9500 0.0500 15.1 0.3 6.5 10:00 6.0000 0.0500 16.5 1.4 28.4 10:05 6.0500 0.0500 19.8 3.3 65.9 10:10 6.1000 0.0500 29.9 10.0 100.3 10:15 6.9500 0.0500 236.6 9.4 187.4 11:40 7.0000 0.0500 245.8 9.2 183.5 11:45

Other titratorsMethod Bet also runs with the following titrators:DL50, DL53, DL55, DL67, DL70ES, DL77



Turbidimetric titration of nonionic surfactants

Instruments: METTLER TOLEDO DL58METTLER TOLEDO AT261ST20A Sample changerPrinter

Methods: 32 f (calibration factor)32 g (content determination)

Accessories: Titration beaker ME-101974Peristaltic pump ME-65241

Indication: DP550 with DIN-LEMOadapter ME-89600

Sample: 5 mL aliquot(2-3 g in 1 L)

Compound: Triton N101Average M=638,86, z=1

Preparation: - 10 mL BaCl2 0.1 mol/L

- 5 mL polyvinyl alcohol solution (PVA)- 40 mL deion. water

Titrant: Sodium tetraphenylboratec(NaTPB)= 0.004 mol/Ladjust the pH at 9-10

Results: METTLER TOLEDO DL58 Titrator V2.0 Mettler-Toledo GmbH 004 Market Support Laboratory

Method 32 f NIO/DP550/Factor 05-Sep-1997 17:12 Measured 05-Sep-1997 17:55 User Cosimo De Caro

ALL RESULTS


1 TritonN101 5.0 mL R1 = 7.091 mL Consumption R2 = 1.799 Factor 2 TritonN101 5.0 mL R1 = 7.090 mL Consumption R2 = 1.799 Factor 3 TritonN101 5.0 mL R1 = 7.085 mL Consumption R2 = 1.801 Factor 4 TritonN101 5.0 mL R1 = 7.091 mL Consumption R2 = 1.799 Factor 5 TritonN101 5.0 mL R1 = 6.875 mL Consumption R2 = 1.856 Factor 6 TritonN101 5.0 mL R1 = 6.844 mL Consumption R2 = 1.853 Factor

STATISTICS Number results R2 n = 4 Mean value x = 1.800 Factor Standard deviation s = 0.00076 Factor Rel. standard deviation srel = 0.042 % Sample No. 5 deleted Sample No. 6 deleted


Principle

• Since the titration reaction is not stoichiometricthe content determination of nonionic surfactantsis based on a comparative titration of a standardsolution.

• A sample of known concentration is titratedaccording to method 32 f. From the titrantconsumption VEQ and the known concentration,a factor R2 (mg surfactant/mL titrant) isdetermined and stored as auxiliary value H2,which is taken into account in the main titration(32 g).

• The sample content determination is performedaccording to method 32 g (see next page).

Comments on method 32 f

• Since no transmission minimum was detected, thecurve was evaluated by the "Standard" procedure.In this case, the same evaluation must be usedwhen titrating the sample (32 g).

• A function "Auxiliary value" allows theautomatic storage of the factor in the installationdata. Method 32 f is a standard method.

• Polyvinyl alcohol solution: Dissolve 3-4 g PVAin ca. 250 mL water by gently warming, and allowit to cool down before addition.

• C2 is the concentration of the standard solution,in this case C2=2.55157 g/L .

E – V curve



ET1 0.0000 943.2 0:15 0.4000 0.4000 941.8 -1.4 -3.6 0:30 0.8000 0.4000 938.4 -3.4 -8.4 0:45 1.2000 0.4000 934.8 -3.6 -9.0 1:00 1.6000 0.4000 928.1 -6.7 -16.8 1:15

6.0000 0.4000 544.9 -68.5 -171.2 4:00 6.4000 0.4000 473.7 -71.2 -178.0 4:15 6.8000 0.4000 403.5 -70.2 -175.4 4:30 7.2000 0.4000 328.1 -75.4 -188.5 4.45 EQP1 7.6000 0.4000 247.9 -80.1 -200.3 5:00 8.0000 0.4000 192.3 -55.6 -139.1 5:15 8.4000 0.2000 159.2 -33.2 -82.9 5:30 8.8000 0.4000 136.7 -22.5 -56.2 5:45 9.2000 0.4000 121.7 -14.9 -37.3 6:00 9.6000 0.4000 111.0 -10.7 -26.8 6:15 10.0000 0.4000 104.4 -6.7 -16.6 6:30


Method 32 f NIO/DP550/Factor Version 05-Sep-1997 17:12

Title Method ID . . . . . . . . . . . . . 32 f Title . . . . . . . . . . . . . . . NIO/DP550/Factor Date/time . . . . . . . . . . . . . 05-Sep-1997 17:12 Sample Sample ID . . . . . . . . . . . . . TritonN101 Entry type . . . . . . . . . . . . . Fixed volume Volume [mL] . . . . . . . . . . . 5.0 Molar mass M . . . . . . . . . . . . 638.86 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . ST20A Pump . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 50.0 Pump . . . . . . . . . . . . . . No Rinse . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 30.0 Conditioning . . . . . . . . . . Yes Time[s] . . . . . . . . . . . 15 Interval . . . . . . . . . . . 1 Rinse . . . . . . . . . . . . No Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 40 Time [s] . . . . . . . . . . . . . . 10 EQP titration Titrant/Sensor Titrant . . . . . . . . . . . . . NaTPB Concentration [mol/L] . . . . . . 0.004 Sensor . . . . . . . . . . . . . DP550 Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . No Titrant addition . . . . . . . . . . Incremental dV [mL] . . . . . . . . . . . . . 0.4 Measure mode . . . . . . . . . . . . Timed increment dt [s] . . . . . . . . . . . . . 15.0 Recognition Threshold . . . . . . . . . . . . 150.0 Steepest jump only . . . . . . . Yes Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Negative Termination at maximum volume [mL] . . . . . 10.0 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . No comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition . . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=VEQ Constant . . . . . . . . . . . . . . Decimal places . . . . . . . . . . . 3 Result unit . . . . . . . . . . . . mL Result name . . . . . . . . . . . . Consumption Statistics . . . . . . . . . . . . . No Calculation Formula . . . . . . . . . . . . . . R2=C2*m/R1 Constant . . . . . . . . . . . . . . C2=2.55157 Decimal places . . . . . . . . . . . 3 Result unit . . . . . . . . . . . . Result name . . . . . . . . . . . . Factor Statistics . . . . . . . . . . . . . Yes Auxiliary value ID . . . . . . . . . . . . . . . . . Factor mg/mL Formula . . . . . . . . . . . . . . H2=x Report Output unit . . . . . . . . . . . . Printer Results . . . . . . . . . . . . . . No All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . Yes Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes dE/dV - V curve . . . . . . . . . . Yes d2E/dV2 - V curve . . . . . . . . . No log dE/dV - V curve . . . . . . . . No E - t curve . . . . . . . . . . . . No V - t curve . . . . . . . . . . . . No

dV/dt - t curve . . . . . . . . . . No

Method 32 f (calibration factor)


Method 32 g (content determination) Comments on method 32 g

• Recovery:1.multiply by the calibration factor H2,2.divide by the sample size m,3.divide again by the concentration of thesample solution, C2.In this case, C2=2.55157 mg/mL.

• R2 gives the recovery of the nonionic surfactantby using the same solution as for the determinationof the calibration factor.

Method 32 g NIO/DP550/Content Version 05-Sep-1997 18:25

Title Method ID . . . . . . . . . . . . . 32 g Title . . . . . . . . . . . . . . . NIO/DP550/Content Date/time . . . . . . . . . . . . . 05-Sep-1997 18:25 Sample Sample ID . . . . . . . . . . . . . TritonN101 Entry type . . . . . . . . . . . . . Fixed volume Volume [mL] . . . . . . . . . . . 5.0 Molar mass M . . . . . . . . . . . . 638.86 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . ST20A Pump . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 50.0 Pump . . . . . . . . . . . . . . No Rinse . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 30.0 Conditioning . . . . . . . . . . Yes Time[s] . . . . . . . . . . . 15 Interval . . . . . . . . . . . 1 Rinse . . . . . . . . . . . . No Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 40 Time [s] . . . . . . . . . . . . . . 10 EQP titration Titrant/Sensor Titrant . . . . . . . . . . . . . NaTPB Concentration [mol/L] . . . . . . 0.004 Sensor . . . . . . . . . . . . . DP550 Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . No Titrant addition . . . . . . . . . . Incremental dV [mL] . . . . . . . . . . . . . 0.4 Measure mode . . . . . . . . . . . . Timed increment dt [s] . . . . . . . . . . . . . 15.0 Recognition Threshold . . . . . . . . . . . . 150.0 Steepest jump only . . . . . . . Yes Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Negative Termination at maximum volume [mL] . . . . . 12.0 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . No comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition . . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=VEQ Constant . . . . . . . . . . . . . . Decimal places . . . . . . . . . . . 3 Result unit . . . . . . . . . . . . mL Result name . . . . . . . . . . . . Consumption Statistics . . . . . . . . . . . . . No Calculation Formula . . . . . . . . . . . . . . R2=H2*R1*100/(m*C2) Constant . . . . . . . . . . . . . . C2=2.55157 Decimal places . . . . . . . . . . . 3 Result unit . . . . . . . . . . . . % Result name . . . . . . . . . . . . Content Statistics . . . . . . . . . . . . . Yes Calculation Formula . . . . . . . . . . . . . . Constant . . . . . . . . . . . . . . Decimal places . . . . . . . . . . . 0 Result unit . . . . . . . . . . . . Result name . . . . . . . . . . . . Statistics . . . . . . . . . . . . . No Report Output unit . . . . . . . . . . . . Printer+Memory Card Results . . . . . . . . . . . . . . No All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . Yes Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes dE/dV - V curve . . . . . . . . . . Yes d2E/dV2 - V curve . . . . . . . . . No log dE/dV - V curve . . . . . . . . No E - t curve . . . . . . . . . . . . No V - t curve . . . . . . . . . . . . No

dV/dt - t curve . . . . . . . . . . No

E – V curve



ET1 0.0000 949.5 0:15 0.4000 0.4000 947.3 -2.2 -5.5 0:30 0.8000 0.4000 943.9 -3.4 -8.4 0:45 1.2000 0.4000 939.0 -4.9 -12.3 1:00 1.6000 0.4000 928.1 -6.7 -16.8 1:15

6.0000 0.4000 547.5 -67.9 -169.6 4:00 6.4000 0.4000 477.6 -69.9 -174.8 4:15 6.8000 0.4000 408.1 -69.5 -173.7 4:30 7.2000 0.4000 331.2 -77.0 -192.4 4:45 EQP1 7.6000 0.4000 254.0 -77.2 -192.9 5:00 8.0000 0.4000 203.3 -50.7 -126.8 5:15 8.4000 0.4000 172.8 -30.5 -76.8 5:30 8.8000 0.4000 151.3 -21.5 -53.6 5:45 9.2000 0.4000 135.6 -15.8 -39.4 6:00 9.6000 0.4000 125.2 -10.3 -25.8 6:15 10.0000 0.4000 118.1 -7.1 -17.8 6:30 10.4000 0.4000 117.4 -0.7 -1.8 6:59 10.8000 0.4000 110.8 -6.6 -16.5 7:14 11.2000 0.4000 109.1 -1.7 -4.2 7:29 11.6000 0.4000 108.3 -0.8 -2.1 7:44 12.0000 0.4000 107.9 -0.4 -1.0 7:59


Other titratorsMethods 32 f and 32 g can also be run with thefollowing titrators:DL50, DL53, DL55DL67, DL70ES, DL77

Author: C. De Caro


General remarks

Principle• Samples of unkown composition are measured and compared against a reference nonionic surfactant, for

instance, nonylphenol ethoxylate with 10 EO (1 EO: CH2-CH

2-O ) or a pure solution of the nonionic

surfactant present in the sample.• Nonionic surfactants form a complex with barium cations Ba2+. The formed complex has a positive charge

-a pseudo-cationic surfactant. The analyte can be titrated with a bulky anion which is able to precipitate thepseudo-cationic surfactant.Tetraphenylborate (TPB, (C

6H

5)

4B- ) is used to form an insoluble complex with the pseudo-cationic surfactant.

The reaction is not stoichiometric, i.e., there is no well-defined ratio between the amount of substance ofthe two species.Thus, a calibration titration with a standard solution of know concentration must be performed beforetitration of the sample. Its result, a calibration factor, is then used in the calculation of the sample titration.

Titration technique• Use the same surfactant concentration for both methods 32 f (factor) and 32 g (content). Choose the sample

volume to get a titrant consumption of about 5 mL.• Unknown sample:

First run a titration with termination at maximum volume to record the whole titration curve. In this way,the parameters and the evaluation procedure of the method can be easily optimized.


Method 32 g NIO/DP550/Content 05-Sep-1997 18:25 Measured 05-Sep-1997 19:09 User Cosimo De Caro

ALL RESULTS


1 TritonN101 5.0 mL R1 = 6.889 mL Consumption R2 = 97.192 % Content 2 TritonN101 5.0 mL R1 = 7.056 mL Consumption R2 = 99.557 % Content 3 TritonN101 5.0 mL R1 = 7.055 mL Consumption R2 = 99.535 % Content 4 TritonN101 5.0 mL R1 = 6.711 mL Consumption R2 = 94.681 % Content 5 TritonN101 5.0 mL R1 = 6.863 mL Consumption R2 = 96.835 % Content 6 TritonN101 5.0 mL R1 = 6.888 mL Consumption R2 = 97.185 % Content

STATISTICS Number results R2 n = 5 Mean value x = 98.061 % Content Standard deviation s = 1.36139 % Content Rel. standard deviation srel = 1.390 % Sample No. 4 deleted


Colorimetric Two-Phase TitrationsPrincipleThe two-phase titration was first described by Epton in 1947 (For a review, see ref. [1-6] ). It soonbecame a widely accepted method and was also developed to a standard method recognized by ASTM,BSI and DIN [7].This method allows the determination of ionic surfactants by titration with a counter-ionic surfactantin a medium consisting of an aqueous (H

2O) and a chloroform (CHCl

3) phase. For instance, anionic

surfactants such as SDS can be titrated with a cationic one such as CPC, Hyamine 1622 or DDMICl(1,3-Didecyl-2-methyl-imidazolium-chloride) in the presence of an indicator which consists of a mixtureof a cationic dye (dimidium bromide) and an anionic dye (disulfine blue). Similarly, cationic surfactantscan be titrated with anionic surfactants using the same mixed indicator solution.

Example: Titration of an anionic surfactant with a cationic surfactant

• The anionic surfactant and the cationic dye give a non-polar pink complex which is soluble inchloroform and insoluble in water.

• After each titrant increment, the solution is stirred vigorously and then allowed to separate• In the course of titration, the titrant displaces the cationic dye and the pink colour slowly disappears

from the chloroform phase. The positively charged dye passes into the aqueous phase.• At the EQP, the pink colour disappears, the chloroform phase is colourless and an excess of titrant

forms a non-polar blue complex with the anionic dye in the chloroform phase.

Anionic surfactant

Titrant addition Stirring Data acquisition

Principle

At EQP

Before EQP EQP After EQP

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H2O

CHCl3

H2O

CHCl3

Pink

Pink Blue


Classical two-phase titrationAfter addition of a titrant increment, the sample is stirred vigorously during a defined time period toallow reaction of the titrant with the analyte and its extraction into the organic phase (chloroform).The strong stirring is stopped and the two phases separate. This cycle is performed until a titrantexcess leads to a clear colour change in the organic phase:

Addition of increment ➞ Stirring ➞ Separation of the two phases ➞ Measure

Automation of classical two-phase titration with the DL58 titrator (DL53+/DL55+)This sequence can be automated using a special function of the DL58 titrator called «Two-phasetitration» (2P). This function allows an incremental titrant addition and in the measure mode twodifferent times have to be defined:

Mixing time: The solution is stirred vigorously (e.g., speed: 70%) and the complex betweenanalyte and titrant is extracted into chloroform.

Separation time: The solution is stirred slowly (e.g. speed 10%) and the two phases can separate.The signal is acquired at the end of the separation time.

The mixing and the separation times are defined in the parameter "Measure mode" :

Mixing time , separation time, and stirrer speed during separation time are the most importantparameters to be optimized in a «Two-phase titration»-function.

Since the function is contained in a special method of the DL58 titrator, the 2P- titration can only bedeveloped using this titrator. Nevertheless the application can also be run on a DL53 or DL55 titratorby means of an extension dongle (i.e., DL53 ➞ DL53+ ; DL55 ➞ DL55+).

Water bubbles can coat the mirror and the window of the phototrode affecting the signal acquisition.To avoid this, a special two-phase titration beaker (ME-51'107'655) was developed.

Lateral port for thephototrode

Measure mode METHOD

Mixing time [s] 15Separation time [s] 50Stirrer speed (sepn time) [%] 10

Water

Chloroform



Standardization of Hyamine by Two-Phase Titration (DL58)

Sample: SDS, c(SDS) = 0.004 mol/L5 mL aliquot

Compound: Sodium dodecylsulphate (SDS)

Preparation: - 10 mL mixed indicator- 50 mL Chloroform- 10 mL deion. water


Results: Method 91003 Titer AT/SDS/Ept.P./Chl++ 03-Jun-1997 12:06 Measured 03-Jun-1997 13:06 User rd

ALL RESULTS


1 SDS 5.0 mL R1 = 1.0525 Titer Hyamine 2 SDS 5.0 mL R1 = 1.0559 Titer Hyamine 3 SDS 5.0 mL R1 = 1.0832 Titer Hyamine 4 SDS 5.0 mL R1 = 1.0331 Titer Hyamine 5 SDS 5.0 mL R1 = 1.0809 Titer Hyamine 6 SDS 5.0 mL R1 = 1.0909 Titer Hyamine

STATISTICS Number results R1 n = 6 Mean value x = 1.0661 Titer Hyamine Standard deviation s = 0.02235 Titer Hyamine Rel. standard deviation srel = 2.097 %

TITER Titrant Hyamine 0.004 mol/L New titer t = 1.06608

Instruments: METTLER TOLEDO DL58METTLER TOLEDO AT261HP Printer

Method: 91003

Accessories: 2P-Titration beaker 51107655(or ME-101446 with ST20A)



Method 91003 Titer AT/SDS/Ept.P./Chl++ Version 03-Jun-1997 12:06

Title Method ID . . . . . . . . . . . . . 91003 Title . . . . . . . . . . . . . . . Titer AT/SDS/Ept.P./Chl++ Date/time . . . . . . . . . . . . . 03-Jun-1997 12:06 Sample Sample ID . . . . . . . . . . . . . SDS Entry type . . . . . . . . . . . . . Fixed volume Volume [mL] . . . . . . . . . . . 5.0 Molar mass M . . . . . . . . . . . . 288.38 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . ST20A Pump . . . . . . . . . . . . . . No Pump . . . . . . . . . . . . . . No Rinse . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 30.0 Conditioning . . . . . . . . . . No Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 75 Time [s] . . . . . . . . . . . . . . 30 Two-phase Titration Titrant/Sensor Titrant . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . 0.004 Sensor . . . . . . . . . . . . . DP550 Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . to volume Volume [mL] . . . . . . . . . . . 3 Waiting time [mL] . . . . . . . . 15 Titrant addition ∆V [mL] . . . . . . . . . . . . . 0.15 Measure mode Mixing time [s] . . . . . . . . . 20.0 Separation time [s] . . . . . . . 30.0 Stirrer speed (sepn time) [%] . . 25 Recognition Threshold . . . . . . . . . . . . 8.0 Steepest jump only . . . . . . . Yes Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Positive Termination at maximum volume [mL] . . . . . 6.0 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . No comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition = . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=m/(VEQ*c*C) Constant . . . . . . . . . . . . . . C=1/(H1*z) Decimal places . . . . . . . . . . . 4 Result unit . . . . . . . . . . . . Result name . . . . . . . . . . . . Titer Hyamine Statistics . . . . . . . . . . . . . Yes Titer Titrant . . . . . . . . . . . . . . Hyamine Concentration [moL/L] . . . . . . . 0.004 Formel t = . . . . . . . . . . . . x Report Output unit . . . . . . . . . . . . Printer Results . . . . . . . . . . . . . . Yes All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . Yes Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - V curve . . . . . . . . . . No ∆

2E/ ∆V

2 - V curve . . . . . . . . . No

log ∆E/ ∆V - V curve . . . . . . . . No E - t curve . . . . . . . . . . . . No V - t curve . . . . . . . . . . . . No ∆V/ ∆t - ∆t curve . . . . . . . . . . No

Method

Other titrators

Method 91003 also runs with the following titrators:DL53+, DL55+ (extension dongle)

Author: D. Rehwald

Preparation of the mixed indicator solution [8]

Dimidium bromide:Weigh accurately 0.2 g into a 100 mL volumetric flaskand dissolve the dye with 10% (V/

V) ethanol. If

necessary, warm gently to achieve completedissolution. After cooling, fill with 10% (V/

V) ethanol

to the mark.Disulfine Blue:Weigh accurately 0.1 g into a second 100 mLvolumetric flask and dissolve the dye with 10% (V/

V)

ethanol. If necessary, warm gently to achieve completedissolution. After cooling, fill with 10% (V/

V) ethanol

to the mark.Mixed indicator solution:10 mL Dimidium bromide solution, 10 mL disulfineblue solution and 10 mL 2.5 mol/L (245 g/L) sulfuricacid solution (be careful! the solution becomes hot!)are poured into a 250 mL volumetric flask. Thesolution is diluted to the mark with distilled water. Ifnot used, store in the dark .Comment: The mixed indicator solution can be storednot longer than 4-5 days.

Comments on method

• The phototrode was dipped into chloroform(lower phase).

• The appropriate stirring speed during separationtime must be chosen to avoid formation of waterbubbles in the measuring cell of the phototrode.If this is not possible, then use the special 2P-titration vessel 51107655. In this application it wasstill possible to work with glass beakers 101446and a ST20A sample changer since water bubblesdid not severely affect the transmission signal.

• After each sample the phototrode is thoroughlyrinsed with water to clean the mirror surface. Ifnecessary, a conditioning step can be defined toensure a complete cleaning of the sensor.

• CAUTION: Chloroform is toxic. It is recommen-ded to work in a fume hood.

• H1 indicates the concentration of the standardsolution.

Waste disposalSeparation and distillation of chloroform to be usedagain, or disposal as special waste Neutralization ofthe aqueous phase.

E – V curve



Determination of anionic surfactants by Two-Phase Titration (DL58)

Sample: Liquid detergents10 mL aliquot with 0.1 g

Compound: Various anionic surfactants

Preparation: - 10 mL mixed indicator- 10 mL chloroform- 40 mL distilled water


Standard: Sodium dodecylsulphate (SDS)

Results: Method 91004 2-Phasen-Titr./Epton 17-Mar-1997 21:06 Measured 17-Mar-1997 23:35 User rd

ALL RESULTS


1 Liq. Det 4 0.1 g R1 = 13.61 % Content R2 = 139.6 mg/g Content AT 2 Liq. Det 4 0.1 g R1 = 13.57 % Content R2 = 139.2 mg/g Content AT 3 Liq. Det 4 0.1 g R1 = 13.46 % Content R2 = 138.1 mg/g Content AT 4 Liq. Det 4 0.1 g R1 = 13.35 % Content R2 = 137.0 mg/g Content AT 5 Liq. Det 4 0.1 g R1 = 13.41 % Content R2 = 137.6 mg/g Content AT

STATISTICS Number results R1 n = 5 Mean value x = 13.48 % Content Standard deviation s = 0.10555 % Content Rel. standard deviation srel = 0.783 %

STATISTICS Number results R2 n = 5 Mean value x = 138.3 mg/g Content AT Standard deviation s = 1.08265 mg/g Content AT Rel. standard deviation srel = 0.783 %

Instruments: METTLER TOLEDO DL58METTLER TOLEDO AT261HP Printer

Method: 91004

Accessories: 2P-Titration beaker 51107655(DP550 in Chloroform)Titration beaker ME-101446(DP550 in Water)



Method 91004 2-Phasen-Titr./Epton Version 17-Mar-1997 21:06

Title Method ID . . . . . . . . . . . . . 91004 Title . . . . . . . . . . . . . . . 2-Phasen-Titr./Epton Date/time . . . . . . . . . . . . . 17-Mar-1997 21:06 Sample Sample ID . . . . . . . . . . . . . Liq. Det. 4 Entry type . . . . . . . . . . . . . Weight Lower limit [g] . . . . . . . . . 0.1 Upper limit [g] . . . . . . . . . 0.5 Molar mass M . . . . . . . . . . . . 288.38 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . Stand 1 Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 65 Time [s] . . . . . . . . . . . . . . 10 Two-phase Titration Titrant/Sensor Titrant . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . 0.02 Sensor . . . . . . . . . . . . . DP550 Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . No Titrant addition ∆V [mL] . . . . . . . . . . . . . 0.1 Measure mode Mixing time [s] . . . . . . . . . 30.0 Separation time [s] . . . . . . . 45.0 Stirrer speed (sepn time) [%] . . 15 Recognition Threshold . . . . . . . . . . . . 8.0 Steepest jump only . . . . . . . No Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Negative Termination at maximum volume [mL] . . . . . 4.0 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . Yes n = . . . . . . . . . . . . . 1 comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition = . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=Q*C/m Constant . . . . . . . . . . . . . . C=M/(10*z) Decimal places . . . . . . . . . . . 2 Result unit . . . . . . . . . . . . % Result name . . . . . . . . . . . . Content Statistics . . . . . . . . . . . . . Yes Calculation Formula . . . . . . . . . . . . . . R2=(VEQ*t*5.7676)/m Constant . . . . . . . . . . . . . . Decimal places . . . . . . . . . . . 1 Result unit . . . . . . . . . . . . mg/g Result name . . . . . . . . . . . . Content AT Statistics . . . . . . . . . . . . . Yes Report Output unit . . . . . . . . . . . . Printer Results . . . . . . . . . . . . . . Yes All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . Yes Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - V curve . . . . . . . . . . No ∆

2E/ ∆V

2 - V curve . . . . . . . . . No


Method

Other titrators

Method 91004 also runs with the followingtitrators:DL53+, DL55+ (extension dongle)

Author: D. Rehwald

E – V curve



V) ethanol. If

necessary, warm gently to achieve completedissolution. After cooling, fill with 10% (V/

V) ethanol


V)

ethanol. If necessary, warm gently to achieve completedissolution. After cooling, fill with 10% (V/

V) ethanol


Comments on method

• The signal was monitored by a phototrode dippedin the water phase to avoid interference of waterbubbles during the separation time. Since thecolour change is weaker than in the chloroformphase, the signal change at the EQP is also weaker.

• After each sample the phototrode is thoroughlyrinsed with water to clean the mirror surface.

• A sample changer ST20A can be used forautomatic procedure: Enter «ST20A» as titrationstand in the function «Sample». In this case, aconditioning beaker can be placed after eachsample beaker.

• The anionic content AT in unknown samples canbe expressed as sodium laurylsulphate (SDS)amount / Sample size. 1 mL 0.02 mol/L Hyaminecorresponds to 5.7676 mg SDS [9]. This is givenin calculation R2.


Results

General remarks

• To avoid interferences by water bubbles during separation time, the signal can be also recorded in thewater phase (liq. det. 3 and 4). In this case, the amount of chloroform is consistently reduced. The curveshows a lower light transmission due to emulsion which is formed during stirring.

• Each sample must be tested to obtain the optimal method parameters for automatic titration.It is recommended to first perform a titration without termination after the first equivalence point to obtainthe whole titration curve. In this way, the appropriate parameters (threshold, evaluation) can then be selected.

• Predispensing is not used for the analyses of liquid detergents 3 and 4 since it affects the curve profilewhen monitoring the colour change with the phototrode in the water phase.

• CAUTION: Chloroform is toxic. It is recommended to work in a fume hood.

Waste disposal

After separation of the two phases:Organic phase: Chloroform can be distilled and used again, or must be classified as special waste.Aqueous phase: Neutralization of the aqueous phase.


Reference: Value given by the producer and mostly based on classical two-phase titration. It indicatesthe total washing active matter.

Product Nominal Reference No. of Content RSD Remarks

(Surfactant component) value, % value, % samples % %

Liquid detergent 1 18.0 17.1 6 17.84 3.43 Stir time: 5 s (Speed: 75%)

Average molar mass: 387 pH 3 pH 3 Separation time: 30 s (30%)

Fatty alcohol ether sulphate 10.0 INC: 0.2 mL, c(Hya)= 0.01 M

Secondary alkanesulphonate 6.0 detection in chloroform phase

Cocoamidopropylbetaine 2.0 2P-Titration beaker 51107655

Conc. liquid detergent 2 38.5 32.8 5 31.13 3.17 Stir time: 5 s (Speed: 70%)

Average molar mass: 362 pH 3 pH 3 Separation time: 50 s (20%)

Fatty alcohol ether sulphate 11.0 INC: 0.15 mL, c(Hya)=0.01 M

Secondary alkanesulphonate 20.0 detection in chloroform phase

Cocoamidopropylbetaine 3.5 2P-Titration beaker 51107655

Nonionic surfactant (7 EO, M=520) 4.0

Liquid detergent 3 33.0 - 5 33.10 0.5 Stir time: 10 s (Speed: 70%)

Anionic surfactant A (M=346) 27.0 pH 1-2 Separation time: 4 s (10%)

Anionic surfactant B (M=385) 6.0 INC: 0.2 mL, c(Hya)=0.01 M--> Average: 353.09 detection in water phase

Glass beaker 101446

Liquid detergent 4Anionic surfactant as SDS 15-30.0 14.18 5 13.48 0.78 see method page 25

(M=288.38) pH 1-2 pH 1-2


Automated two-phase titrations with the DL77 titratorThanks to the possibilities of parallel titration and synchronization of analyses A and B of the DL77, theclassical 2P-Titration can be automated as it follows [6]:

1. Analysis A executes an EQP titration with fixed time intervals and fixed titrant increments;2. Analysis B controls the stirring sequence.3. Analyses A and B are synchronised by a short circuit plug inserted at the RS232 interface (DL67/70ES/77

manual, chap. 11, p. 12). Pins 2 and 3 of short circuit plug are first connected before inserting the plug inthe RS232 interface.

In the titration method (Analysis A), the sequence of titrant addition and stirring must be coordinated andsynchronised. Therefore it is important to use exactly the settings indicated in the method.

Principle

1) Analysis B must be started before analysis A. The number of samples is defined in the «Sample» functionof analysis A. Any stirrer can be chosen for analysis A, while Stirrer 1 is reserved for analysis B.

2) Analysis B sends a signal to A and waits for a signal to continue.3) Analysis A sends a signal to B and steps to the next function, Analysis B can continue.

No more than 6 «Stir» functions can be used in one titration method. Thus, a «Measure» function is usedfor stirring in analysis B and has no other purpose. After this time analysis B sends a signal to A and waitsfor a signal until in Analysis A the titration is started.

4) In analysis A a «Dispense» function is used to predispense the titrant. The volume depends on the samplesize and has to be changed when a different sample is measured.

5) Analysis A sends a signal to B and continues, Analysis B starts the stirring sequence.6) The 6 functions «Stir» in Analysis B cover three increment additions for each sample defined in the

second «Sample» function in B:A: adds increment and waits 60 s (Measure mode TFIX , ∆t = 60 s).B: stir vigorously (14 s) and stir slowly (44 s), then signal acquisition, three times.Therefore the number of samples of the second «Sample» function of analysis B depends on the maximumvolume defined in Analysis A (termination).

Analysis A (Titration) Analysis B (Stirring)TITLE TITLESAMPLE SAMPLESYNC Send:Start SYNC Wait: StartDISPENSE MEASURE

(Used for Stirring)STIRSYNC Send: Start Cycle SYNC Wait: Start Cycle

MEASURE(Used for Stirring)SAMPLE n = 8

TITRATIONadd Increment/measurewait 60 s STIR: 14 s 100%

STIR: 44 s 15%

add Increment/measurewait 60 s STIR: 15 s 100%

STIR: 45 s 15%

add Increment/measurewait 60 s STIR: 15 s 100%

STIR: 45 s 100%

CALCULATION CALCULATIONSTATISTICS STATISTICSRECORD RECORD

1)

2)3)4)

5)

6)6)



Two-Phase Titration with DL77: Standardization of Hyamine 1622

Instruments: METTLER TOLEDO DL77Interface option RS232 ME-25690Short circuit plug ME-89144METTLER TOLEDO AT261Printer HP Deskjet

Method: "Phas" & "Stir"

Accessories: 2P-Titration beakerME-51107655

Indication: DP550 at Sensor 2 with DIN-LEMO adapter ME-89600

Sample: Sodium dodecylsulphate (SDS)5 mL , c(SDS) = 0.004 M

Compound: SDS, M = 288.38 z = 1

Preparation: - 10 mL Mixed indicator- 10 mL Water- 50 mL Chloroform


Results: METTLER DL77 Titrator V3.1 Mettler-Toledo AG Market Support Analytical

Method Phas 01-Jul-1994 12:59 User Measured 01-Jul-1994 17:04

RESULTS

No ID1 ID2 Sample amount and results

1/1 5.0 mL Fixed volume U R1 = 1.00461 Titer Hyamine 1/2 5.0 mL Fixed volume U R1 = 1.00146 Titer Hyamine 1/3 5.0 mL Fixed volume U R1 = 1.00485 Titer Hyamine 1/4 5.0 mL Fixed volume U R1 = 1.00061 Titer Hyamine 1/5 5.0 mL Fixed volume U R1 = 1.01063 Titer Hyamine 1/6 5.0 mL Fixed volume U R1 = 1.00375 Titer Hyamine

STATISTICS Number results R1 n = 6 Mean value x = 1.00432 Titer Hyamine Standard deviation s = 0.003536 Titer Hyamine Rel. standard deviation srel = 0.352 % Outlier test: no outliers!



Method A Method Phas Determination of anionic T Version 01-Jul-1994 12:59

Title Method ID . . . . . . . . . . . . . Phas Title . . . . . . . . . . . . . . . Determination of

anionic T Date/time . . . . . . . . . . . . . 01-Jul-1994 12:59 Sample Number samples . . . . . . . . . . . 6 Titration stand . . . . . . . . . . ST20 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 5.0 ID1 . . . . . . . . . . . . . . . . SDS Molar mass M . . . . . . . . . . . . 288.38 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . Manual Sync Sync mode . . . . . . . . . . . . . Send Code . . . . . . . . . . . . . . . . 1 Comment . . . . . . . . . . . . . . Dispense Titrant . . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . . 0.004 Volume [mL] . . . . . . . . . . . . 4 Stir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 30

Sync Sync mode . . . . . . . . . . . . . Send Code . . . . . . . . . . . . . . . . 2 Comment . . . . . . . . . . . . . . Start B Method Titration Titrant . . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . . 0.004 Sensor . . . . . . . . . . . . . . . DP550 Unit of meas. . . . . . . . . . . . mV Titration mode . . . . . . . . . . . EQP Predispensing 1 . . . . . . . . . mL Volume [mL] . . . . . . . . . 0 Titrant addition . . . . . . . . INC ∆V [mL] . . . . . . . . . . . 0.1 Measure mode . . . . . . . . . . TFIX ∆t [s] . . . . . . . . . . . . 60.0 Threshold . . . . . . . . . . . . 800.0 EQP range . . . . . . . . . . . . Yes Limit A . . . . . . . . . . . 100 Limit B . . . . . . . . . . . 1000 Maximum volume [mL] . . . . . . . 1.4 Evaluation procedure . . . . . . Standard Steepest jump only . . . . . . . Yes Stop for reevaluation . . . . . . Yes Condition . . . . . . . . . . neq=0 Calculation Result name . . . . . . . . . . . . Titer Hyamine Formula . . . . . . . . . . . . . . R=U/((Q+QDISP)*C) Constant . . . . . . . . . . . . . . C=1/(H1*z) Result unit . . . . . . . . . . . . Decimal places . . . . . . . . . . . 5 Record Output unit . . . . . . . . . . . . Printer Table of values . . . . . . . . . . Yes E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - curve . . . . . . . . . . . Yes Statistics Ri (i=index) . . . . . . . . . . . . R1 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes

Outlier test . . . . . . . . . . . . Yes Titer Titrant . . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . . 0.004 Formula t = . . . . . . . . . . . x Condition . . . . . . . . . . . . . Yes Condition . . . . . . . . . . . . 0.85 < x < 1.15 Record Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes

Method B Method Stir Version 30-Jun-1994 13:03

Title Method ID . . . . . . . . . . . . . Stir Title . . . . . . . . . . . . . . . Date/time . . . . . . . . . . . . . 30-Jun-1994 13:03 Sync Sync mode . . . . . . . . . . . . . Send/Wait Code . . . . . . . . . . . . . . . . 1 Comment . . . . . . . . . . . . . . Sample Number samples . . . . . . . . . . . 1 Titration stand . . . . . . . . . . Auto stand Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 1.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 100.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . Manual

Measure Sensor . . . . . . . . . . . . . . . DG111-SC Unit of meas. . . . . . . . . . . . mV

∆E [mL] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . . 1.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 20.0 t(max) [s] . . . . . . . . . . . . . 20.0 Sync Sync mode . . . . . . . . . . . . . Send/Wait Code . . . . . . . . . . . . . . . . 2 Comment . . . . . . . . . . . . . .


∆E [mL] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . . 1.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 5.0 t(max) [s] . . . . . . . . . . . . . 5.0 Sample Number samples . . . . . . . . . . . 5 Titration stand . . . . . . . . . . Auto stand Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 1.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 100.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 100 Time [s] . . . . . . . . . . . . . . 10 Stir Speed [%] . . . . . . . . . . . . . 15 Time [s] . . . . . . . . . . . . . . 48 Stir Speed [%] . . . . . . . . . . . . . 100 Time [s] . . . . . . . . . . . . . . 11 Stir Speed [%] . . . . . . . . . . . . . 15 Time [s] . . . . . . . . . . . . . . 49 Stir Speed [%] . . . . . . . . . . . . . 100 Time [s] . . . . . . . . . . . . . . 11 Stir Speed [%] . . . . . . . . . . . . . 15 Time [s] . . . . . . . . . . . . . . 49 Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R=1 Constant . . . . . . . . . . . . . . C=1 Result unit . . . . . . . . . . . . % Decimal places . . . . . . . . . . . 5 Statistics Ri (i=index) . . . . . . . . . . . . R1 Standard deviation s . . . . . . . . Yes

Method A: maximum volume 1.4 mL, increments 0.1 (14 increments)

Method B: 5 samples , 3 stir cycles for each sample corresponds to 15 increments.


Preparation of the mixed indicator solution

Dimidium bromide:Weigh accurately 0.5 g into a 50 mL beaker and addbetween 20-30 mL of 10% (V/

V) ethanol to dissolve

the dye. If necessary, gently warm up the solution.Stir until the dye is dissolved and transfer the solutioninto a 250 mL volumetric flask. Rinse the beakers with10% v/v ethanol and dilute the solution to the markwith ethanol.Disulfine Blue:Weigh accurately 0.25 g into a second 50 mL beakerand add between 20-30 mL of 10% (V/

V) ethanol to

dissolve the dye. If necessary, gently warm up thesolution. Stir until the dye is dissolved and transferthe solution into a 250 mL volumetric flask. Rinsethe beakers with 10% v/v ethanol and dilute thesolution to the mark with ethanol.Mixed indicator solution:Add 200 mL of distilled water into a 500 mLvolumetric flask. Add 20 mL of dimidium bromidesolution and 20 mL of disulfine Blue solution. Gentlypour 20 mL of 2.5 mol/L (245 g/L) sulfuric acidsolution (be careful! the solution becomes hot!). Diluteto the mark with distilled water. If not used, store inthe dark.Comment: The mixed indicator solution can be storednot longer than 4-5 days.

Synchronization of the two analyses A and B

To synchronize both analyses A and B, the DL77titrator must be equipped with a RS232 Interface Op-tion (ME-25690). A 8 pin cable connector (ME-89144)can be used to prepare a short circuit plug (SeeOperating Instructions "RS232 C InterfaceDescription", ME-709165, provided with the RS Op-tion).

Comments on method

1) The colour change is monitored with a DP550Phototrode in the organic phase.

2) During separation of the two phases it canhappen that water bubbles are trapped in thephototrode cell of the screw-on mirror assembly.To avoid this situation, a special two-phase (2P)beaker with a lateral port was used (ME-51107655). In this way, the phototrode was notinserted vertically, and therefore the formationof water bubbles was avoided:

General remarks

CAUTION: Chloroform is toxic. It is recommendedto work in a fume hood.

Waste disposal

Organic phase: Chloroform can be distilled and usedagain or must be classified as special waste.Aqueous phase: Neutralization of the aqueous phase.

Author: Ch. Walter

E – V curve

Table of measured values (Method A)

Volume Increment Signal Change 1st deriv. Time mL mL mV mV mV/mL min:s

ET1 0.0000 13.0 1:00 ET2 0.0000 0.0000 53.6 40.6 2:00 0.1000 0.1000 53.7 0.1 0.7 3:00 0.2000 0.1000 86.4 32.7 326.9 4:00 0.3000 0.1000 114.5 28.1 281.4 5:00 0.4000 0.1000 127.6 13.1 130.9 6:00 0.5000 0.1000 136.8 9.2 92.4 7:00 0.6000 0.1000 162.3 25.2 254.8 8:00 0.7000 0.1000 219.8 57.5 547.7 9:00 0.8000 0.1000 335.2 115.4 1154.3 10:00 EQP1 0.9000 0.1000 520.1 184.9 1848.7 11:00 1.0000 0.1000 620.5 100.4 1004.5 12:00 1.1000 0.1000 674.0 53.5 534.8 13:00 1.2000 0.1000 741.6 67.6 676.2 14:00 1.3000 0.1000 774.6 33.0 329.7 15:00 1.4000 0.1000 868.1 93.4 934.5 16:00

lateral port forthe phototrode



Two-Phase Titration with DL77: Anionic surfactants determination

Sample: Various productsca. 0.05 g / sample

Compound: Anionic surfactants(calc. as SDS, M=288.38, z=1)

Preparation: - 10 mL mixed indicator- 10 mL water- 50 mL chloroform

Titrant: Hyamine 1622c(Hyamine) = 0.004 mol/L

Standard: Sodium dodecylsulphate(SDS)

Results:

Instruments: METTLER TOLEDO DL77Interface option RS232 ME-25960Short circuit plug ME-89144METTLER TOLEDO AT261Printer HP Deskjet

Method: "Hany" & "Sti2"

Accessories: 2P-Titration beakerME-51107655

Indication: DP550 at Sensor 2 with DIN-LEMO adapter cable ME-89600

METTLER DL77 Titrator V3.1 Mettler-Toledo AG Market Support Analytical

Method Hany Determination of anionic S 21-Jul-1994 16:03 User Ch. Walter Measured 21-Jul-1994 18:41

RESULTS

No ID1 ID2 Sample size and results

1/1 0.05011 g Weight m R1 = 15.5941 % Content 1/2 0.05011 g Weight m R1 = 15.9426 % Content 1/3 0.05011 g Weight m R1 = 16.0844 % Content 1/4 0.05011 g Weight m R1 = 15.8882 % Content 1/5 0.05011 g Weight m R1 = 15.9154 % Content 1/6 0.05011 g Weight m R1 = 15.8913 % Content

STATISTICS Number results R1 n = 6 Mean value x = 15.8860 % Content Standard deviation s = 0.160392 % Content Rel. standard deviation srel = 1.010 %


Method A Method Hany Determination of anionic S Version 21-Jul-1994 16:03

Title Method ID . . . . . . . . . . . . . Hany Title . . . . . . . . . . . . . . . Determination of

anionic S Date/time . . . . . . . . . . . . . 21-Jul-1994 16:03 Sample Number samples . . . . . . . . . . . 6 Titration stand . . . . . . . . . . ST20 1 Entry type . . . . . . . . . . . . . Weight Lower limit [g] . . . . . . . . . 0.04 Upper limit [g] . . . . . . . . . 0.06 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 432 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . Manual Sync Sync mode . . . . . . . . . . . . . Send Code . . . . . . . . . . . . . . . . 1 Comment . . . . . . . . . . . . . . Dispense Titrant . . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . . 0.004 Volume [mL] . . . . . . . . . . . . 4 Stir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 30

Sync Sync mode . . . . . . . . . . . . . Send Code . . . . . . . . . . . . . . . . 2 Comment . . . . . . . . . . . . . . Start B Method Titration Titrant . . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . . 0.004 Sensor . . . . . . . . . . . . . . . DP550 Unit of meas. . . . . . . . . . . . mV Titration mode . . . . . . . . . . . EQP Predispensing 1 . . . . . . . . . mL Volume [mL] . . . . . . . . . 0 Titrant addition . . . . . . . . INC ∆V [mL] . . . . . . . . . . . 0.05 Measure mode . . . . . . . . . . TFIX ∆t [s] . . . . . . . . . . . . 60.0 Threshold . . . . . . . . . . . . 800.0 EQP range . . . . . . . . . . . . Yes Limit A . . . . . . . . . . . 100 Limit B . . . . . . . . . . . 1000 Maximum volume [mL] . . . . . . . 1.0 Evaluation procedure . . . . . . Standard Steepest jump only . . . . . . . Yes Stop for reevaluation . . . . . . Yes Condition . . . . . . . . . . neq=0 Calculation Result name . . . . . . . . . . . . Content Formula . . . . . . . . . . . . . . R=(Q+QDISP)*C/m Constant . . . . . . . . . . . . . . C=M/(10*z) Result unit . . . . . . . . . . . . % Decimal places . . . . . . . . . . . 4 Record Output unit . . . . . . . . . . . . Printer Table of values . . . . . . . . . . Yes E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - curve . . . . . . . . . . . Yes Conditioning Interval . . . . . . . . . . . . . . 1 Time [s] . . . . . . . . . . . . . . 20 Statistics Ri (i=index) . . . . . . . . . . . . R1 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes

Outlier test . . . . . . . . . . . . Yes Record Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes

Variable parameters

Method B Method Sti2 Version 21-Jul-1994 15:37

Title Method ID . . . . . . . . . . . . . Sti2 Title . . . . . . . . . . . . . . . Date/time . . . . . . . . . . . . . 21-Jul-1994 15:37 Sync Sync mode . . . . . . . . . . . . . Send/Wait Code . . . . . . . . . . . . . . . . 1 Comment . . . . . . . . . . . . . . Sample Number samples . . . . . . . . . . . 1 Titration stand . . . . . . . . . . Auto stand Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 1.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 100.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . Manual


∆E [mL] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . . 1.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 20.0 t(max) [s] . . . . . . . . . . . . . 20.0 Sync Sync mode . . . . . . . . . . . . . Send/Wait Code . . . . . . . . . . . . . . . . 2 Comment . . . . . . . . . . . . . .


∆E [mL] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . . 1.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 5.0 t(max) [s] . . . . . . . . . . . . . 5.0 Sample Number samples . . . . . . . . . . . 7 Titration stand . . . . . . . . . . Auto stand Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 1.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 100.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 100 Time [s] . . . . . . . . . . . . . . 10 Stir Speed [%] . . . . . . . . . . . . . 15 Time [s] . . . . . . . . . . . . . . 48 Stir Speed [%] . . . . . . . . . . . . . 100 Time [s] . . . . . . . . . . . . . . 11 Stir Speed [%] . . . . . . . . . . . . . 15 Time [s] . . . . . . . . . . . . . . 49 Stir Speed [%] . . . . . . . . . . . . . 100 Time [s] . . . . . . . . . . . . . . 11 Stir Speed [%] . . . . . . . . . . . . . 15 Time [s] . . . . . . . . . . . . . . 49 Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R=1 Constant . . . . . . . . . . . . . . C=1 Result unit . . . . . . . . . . . . % Decimal places . . . . . . . . . . . 5 Statistics Ri (i=index) . . . . . . . . . . . . R1 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes

Variable parameters

General remarks

• Method A: maximum volume 1 mL (termination), ∆V 0.05 mL → 20 increments• Method B: 7 samples, 3 cycles (fast stirring/slow stirring) → 21 increments• Each different sample must be tested to obtain the optimal parameters. The rather few differences between

the methods are given in the result table under "remarks" (see next page).


• During separation of the two phases it can happenthat water bubbles are trapped in the phototrodecell of the screw-on mirror assembly.To avoid this situation, a special two-phase (2P)beaker with a lateral port was used (ME-51107655). In this way, the phototrode was notinserted vertically, and therefore the formation ofwater bubbles was avoided:

E – V curve

Author: Ch. Walter

Waste disposal

Organic phase:Chloroform can be distilled and used again or mustbe classified as special waste.Aqueous phase:Neutralization of the aqueous phase.

• CAUTION: Chloroform is toxic. It isrecommended to work in a fume hood.

Table of measured values Volume Increment Signal Change 1st deriv. Time mL mL mV mV mV/mL min:s

ET1 0.0000 16.3 1:00 ET2 0.0000 0.0000 7.4 -9.0 2:00 0.0500 0.0500 9.8 2.5 49.0 3:00 0.1000 0.0500 9.0 -0.8 -16.8 4:00

0.4000 0.0500 101.1 37.2 744.8 10:00 0.4500 0.0500 142.3 41.2 824.6 11:00 0.5000 0.0500 186.5 44.2 883.4 12:00 0.5500 0.0500 206.4 20.0 399.0 13:00EQP1 0.6000 0.0500 334.7 128.2 2564.8 14:00 0.6500 0.0500 402.8 68.2 1363.6 15:00 0.7000 0.0500 511.3 108.5 2170.0 16:00 0.7500 0.0500 592.1 80.8 1615.6 17:00 0.8000 0.0500 571.6 -20.3 -406.0 18:00 0.8500 0.0500 639.8 68.0 1359.4 19:00 0.9000 0.0500 621.3 -18.5 -369.6 20:00 0.9500 0.0500 701.9 80.6 1612.8 21:00 1.0000 0.0500 700.9 -1.1 -21.0 22:00

lateral port forthe phototrode

ResultsProduct (Surfactant component) Theor. content [%] Samples Content [%] RSD [%] Remarks

Liquid dish washer 15-30.0 6 15.89 1.01 -Anionic surfactant as LAES (M = 432)

Toothpaste (gel) 1 6 1.11 2.73 Analysis A:Anionic surfactant as SDS (M = 288.38) Sample: 0.04-0.06 g

Dispense: 0.5 mL,INC: 0.05 mL, TFIX: 90 sAnalysis B:3x:Stir: 100%, 10 sStir: 40%, 80 s

Shower foam 1 15.0 Analysis A:

Na-Laurylether sulphate (M = 430) 13.0 6 12.05 0.50 Weight (0.06-0.1 g)

5 12.11 0.90 Dispense: 4.5 mL

Betaine (M = 390) 2.0 INC: 0.1 mL, TFIX: 60 s

Maximum volume: 3 mL

Na-laurylether sulphate 71.0 6 63.66 0.44 Analysis A:

Raw material, M = 432 7 63.86 2.02 Weight (0.01-0.03)INC: 0.05 mL, TFIX: 60 s


Mixed two-phase titrationIn the previous sections the classical two-phase titration was automated by the «Two-phase titration»function which is available in the special method «91001 Surfactant determination» of the DL58titrator. The sequence of the classical two-phase titration, i.e.

Addition of incrementMixing and extraction (strong stirring)Separation of the two phases (slow stirring)Signal acquisition

is performed automatically by the titrator.

Although the analysis can be automated, it still can take a long time since the separation of the twophases is the time-consuming step of the classical two-phase titration. To shorten the analysis time, thesignal can be acquired while the titrator is stirring the sample solution at a high speed, and thus withoutphase separation. In this case, a conventional EQP-Titration function can be used for the two-phasetitration [see lit. 8, 9].

A comparison between the mixed two-phase titration and the classical manual procedure has beenpresented in detail by H. Block in 1985 [8]. In particular, the content of anionics and cationics by two-phase titration in various commercially available products were compared. A determination of SDS bymixed two-phase titration shows an excellent agreement with results obtained by classical manualtwo-phase titration [9].

The advantages of the mixed two-phase titration are:

1. automation (a sample changer can be easily used for this operation).2. considerable time saving with respect to the automated classical procedure including the

separation of the phases.3. endpoint detection is operator-independent with respect to the manual procedure.4. The consumption of chloroform is consistently reduced.

Since the signal acquisition is performed in a stirred, heterogeneous two-phase system, the solution isturbid and thus, the light transmission measured by the phototrode is decreased considerably.Nevertheless, the color change of the mixed indicator can still be detected by the sensor.

H. Block describes the signal detection as it follows [9]:«Since during the whole titration a constant stirring speed is maintained, a clear and well-definedphase separation is not visible. The overall colour change is measured in the emulsion. At the beginningthe color is milky-pink, it turns to grey-green at the equivalence point and after the equivalence pointit becomes blue-turquoise.» [citation translated from the German text].In this way, a continuous, mixed two-phase titration is achieved which does not require a phase separationfor the evaluation of the endpoint.

Note that the mixed two-phase titration can be performed with titrators of the DL2x, DL5x and DL7xfamilies and this represents a consistent benefit.



Mixed Two-Phase Titration: Standardization of Hyamine 1622

Sample: SDS, 5 mLc(SDS) = 0.004 mol/L

Compound: Sodium dodecylsulphate (SDS)c(SDS) = 0.004 mol/L

Preparation: - 10 mL mixed indicator- 10 mL chloroform- 40 mL deion. water


Results:


Method: 11

Accessories: Glass beaker ME-101446


Method 11 Titer Hya/Epton mixed 02-Jun-1997 18:39 Measured 03-Jun-1997 19:15 User rd

ALL RESULTS



STATISTICS Number results R1 n = 5 Mean value x = 1.0441 Titer Hyamine Standard deviation s = 0.00239 Titer Hyamine Rel. standard deviation srel = 0.229 % Sample no. 6 deleted



Method 11 Titer Hya/Epton mixed Version 02-Jun-1997 18:39

Title Method ID . . . . . . . . . . . . . 11 Title . . . . . . . . . . . . . . . Titer Hya/Epton mixed Date/time . . . . . . . . . . . . . 02-Jun-1997 18:39 Sample Sample ID . . . . . . . . . . . . . SDS Entry type . . . . . . . . . . . . . Fixed volume Volume [mL] . . . . . . . . . . . 5.0 Molar mass M . . . . . . . . . . . . 288.38 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . ST20A Pump . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 30.0 Stir . . . . . . . . . . . . Yes Pump . . . . . . . . . . . . . . No Rinse . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 30.0 Conditioning . . . . . . . . . . No Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 75 Time [s] . . . . . . . . . . . . . . 15 EQP titration Titrant/Sensor Titrant . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . 0.004 Sensor . . . . . . . . . . . . . DP550 Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . No Titrant addition ∆V [mL] . . . . . . . . . . . . . 0.15 Measure mode . . . . . . . . . . . . Equilibrium controlled ∆E [mV] . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . 1.0 t(min) [s] . . . . . . . . . . . 6.0 t(max) [s] . . . . . . . . . . . 30.0 Recognition Threshold . . . . . . . . . . . . 8.0 Steepest jump only . . . . . . . Yes Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Negative Termination at maximum volume [mL] . . . . . 5.5 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . No comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition = . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=m/(VEQ*c*C) Constant . . . . . . . . . . . . . . C=1/(H1*z) Decimal places . . . . . . . . . . . 4 Result unit . . . . . . . . . . . . Result name . . . . . . . . . . . . Titer Hyamine Statistics . . . . . . . . . . . . . Yes Titer Titrant . . . . . . . . . . . . . . Hyamine Concentration [moL/L] . . . . . . . 0.004 Formel t = . . . . . . . . . . . . x Report Output unit . . . . . . . . . . . . Printer Results . . . . . . . . . . . . . . Yes All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . Yes Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - V curve . . . . . . . . . . No ∆

2E/ ∆V

2 - V curve . . . . . . . . . No


Method

Other titrators

Method 11 also runs with the following titrators:DL50, DL53, DL55DL67, DL70ES, DL77

Author: D. Rehwald



V) ethanol. If

necessary, warm gently to achieve completedissolution. After cooling fill with 10% (V/

V) ethanol


V)

ethanol. If necessary, warm gently to achieve completedissolution. After cooling fill with 10% (V/

V) ethanol


Comments on method

• After each sample the phototrode is thoroughlyrinsed with water to clean the mirror surface.

• A sample changer ST20A is used for automaticprocedure. If necessary, a conditioning step canbe defined to ensure a complete cleaning of thesensor.

• H1 indicates the concentration of the standardsolution.


Waste disposal

After separation of the two phases:Organic phase:Chloroform can be distilled and used again or mustbe classified as special waste.Aqueous phase:Neutralization of the aqueous phase.

E – V curve



Mixed Two-Phase Titration: Anionic surfactants in liquid detergents


Method: 71004

Accessories: Glass beaker ME-101446


Sample: Liquid detergents10 mL aliquot (5g in 500 mL)


Preparation: -10 mL mixed indicator-10 mL chloroform- 40 mL deion. water

Titrant: Hyamine 1622c(Hyamine) = 0.01 mol/L


Results: Method 71004 Eptontitration gerührt 04-Apr-1997 9:34 Measured 04-Apr-1997 10:53 User rd

ALL RESULTS


1 Liq. Det 1 5.0621 g R1 = 14.892 % Content R2 = 113.6 mg/g as SDS 2 Liq. Det 1 5.0621 g R1 = 14.929 % Content R2 = 113.8 mg/g as SDS 3 Liq. Det 1 5.0621 g R1 = 14.940 % Content R2 = 113.9 mg/g as SDS 4 Liq. Det 1 5.0621 g R1 = 14.644 % Content R2 = 111.6 mg/g as SDS 5 Liq. Det 1 5.0621 g R1 = 14.853 % Content R2 = 113.2 mg/g as SDS

STATISTICS Number results R1 n = 5 Mean value x = 14.851 % AT Content Standard deviation s = 0.12088 % AT Content Rel. standard deviation srel = 0.814 %

STATISTICS Number results R2 n = 5 Mean value x = 113.2 % AT/g as SDS Standard deviation s = 0.92170 % AT/g as SDS Rel. standard deviation srel = 0.814 %




V) ethanol. If

necessary, warm gently to achieve completedissolution. After cooling fill with 10% (V/

V) ethanol


V)

ethanol. If necessary, warm gently to achieve completedissolution. After cooling fill with 10% (V/

V) ethanol


Comments on method

• After each sample the phototrode is rinsed withwater.

• The emulsion formed during titration decreasesthe light transmission. Predispensing is not usedsince it affects the curve profile and thus thedetection of the largest signal change.

• The anionic content AT in unknown samples canbe expressed as amount of sodium laurylsulphate(SDS) / Sample size [9]. 1 mL 0.01 mol/LHyamine corresponds to 2.8838 mg SDS. This isgiven in calculation R2.


Waste disposal

After separation of the two phases:Organic phase:Chloroform can be distilled and used again or mustbe classified as special waste.Aqueous phase:Neutralization of the aqueous phase.

Method 71004 Eptontitration gerührt Version 04-Apr-1997 9:34

Title Method ID . . . . . . . . . . . . . 71004 Title . . . . . . . . . . . . . . . Eptontitration gerührt Date/time . . . . . . . . . . . . . 04-Apr-1997 9:34 Sample Sample ID . . . . . . . . . . . . . Liq. Det. 1 Entry type . . . . . . . . . . . . . Weight Lower limit [g] . . . . . . . . . 4.0 Upper limit [g] . . . . . . . . . 5.0 Molar mass M . . . . . . . . . . . . 387 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . Stand 1 Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 40 Time [s] . . . . . . . . . . . . . . 10 EQP titration Titrant/Sensor Titrant . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . 0.01 Sensor . . . . . . . . . . . . . DP550 Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . No Titrant addition . . . . . . . . . . Incremental ∆V [mL] . . . . . . . . . . . . . 0.1 Measure mode . . . . . . . . . . . . Equilibrium controlled ∆E [mV] . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . 1.0 t(min) [s] . . . . . . . . . . . 6.0 t(max) [s] . . . . . . . . . . . 30.0 Recognition Threshold . . . . . . . . . . . . 8.0 Steepest jump only . . . . . . . No Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Negative Termination at maximum volume [mL] . . . . . 12.0 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . Yes n = . . . . . . . . . . . . . 1 comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition = . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=(Q*C)/(m*10/500) Constant . . . . . . . . . . . . . . C=M/(10*z) Decimal places . . . . . . . . . . . 3 Result unit . . . . . . . . . . . . % AT Result name . . . . . . . . . . . . Content Statistics . . . . . . . . . . . . . Yes Calculation Formula . . . . . . . . . . . . . . R2=(VEQ*t*2.8838)/(m/50) Constant . . . . . . . . . . . . . . Decimal places . . . . . . . . . . . 1 Result unit . . . . . . . . . . . . mg AT/g Result name . . . . . . . . . . . . as SDS Statistics . . . . . . . . . . . . . Yes Report Output unit . . . . . . . . . . . . Printer Results . . . . . . . . . . . . . . No All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . Yes Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - V curve . . . . . . . . . . No ∆

2E/ ∆V

2 - V curve . . . . . . . . . No


∆V/ ∆t - t curve . . . . . . . . . . No

Method

Other titrators


Author: D. Rehwald

E – V curve



(Surfactant component) content, % value, % samples % %

Liquid detergent 1 18.0 17.1 6 17.05 1.19 Method: 71004

Average molar mass: 387 pH 3 pH 3

Fatty alcohol ether sulphate 10.0Secondary alkanesulphonate 6.0Cocoamidopropylbetaine 2.0

Conc. liquid detergent 2 38.5 32.8 6 35.30 0.538 Same as 71004

Average molar mass: 362 pH 3 pH 3

Fatty alcohol ether sulphate 11.0Secondary alkanesulphonate 20.0Cocoamidopropylbetaine 3.5Nonionic surfactant (7 EO, M=520) 4.0

Liquid detergent 3 33.0 - 5 32.12 0.019 INC: 0.15 mL

Anionic surfactant A (M=346) 27.0 pH 1-2 additional comp. unknown

Anionic surfactant B (M=385) 6.0--> Average: 353.09

Liquid detergent 4Anionic surfactant as SDS 15-30.0 14.18 5 14.15 0.784 Same as 71004(M=288.38) pH 1-2 pH 1-2 unknown composition


Reference: Value given by the producer and mostly based on classical two-phase titration. It indicatesthe total washing active matter.

General remarks

• Each sample has its own composition, therefore the optimal parameters must be obtained by trying.• Liquid detergents 1 and 2:

The producer gives reference values for the content of washing active matter, 17.1 % and 32.8 % respectively.The value was obtained by classical manual two-phase titration at pH 3.

• Liquid detergent 3:An average value for M was calculated based on the content of the two anionic surfactants A and B , i.e.27% and 6%. Additional components are not specified.

• Liquid detergent 4:The composition is unknown. The anionic content is expressed as SDS.

• In the case of unknown sample or of formulated products:a) first perform a calibration titration on a standard solution of known composition (➡ reference value),b) then compare the reference value with the result obtained by titrating the sample.

Results


Potentiometric titrationsPrincipleThe potential of a solution containing surfactants is measured as a function of the titrant added. Potentiometrictitrations are indicated with a surfactant sensitive electrode (SSE). Usually, a SSE has a PVC membrane optimizedfor the detection of ionic surfactants. The potential is formed by interaction between the ion carrier in themembrane and the analyte in the sample solution. It can be measured against a reference electrode at zerocurrent.

The general composition of a typical SSE is:

• PVC• Plasticizer• Ion carrier

Anionic (cationic) surfactants are titrated with cationic (anionic) surfactants.Near the equivalence point, a precipitate is formed, and the solution becomesturbid.In the case of nonionic surfactants, addition of a specific activator prior totitration is necessary to form a complex between analyte and titrant. The activatoris usually barium chloride, BaCl

2 . The positively charged barium cation Ba2+

forms a complex with the uncharged nonionic surfactant [see ref. 1,4]. As aresult, the surfactant-barium cation complex is positively charged -a pseudo-cationic complex- and therefore can be precipitated by titration with sodiumtetraphenylborate (NaTPB): Tetraphenylborate anions (TPB- ) form a precipitatewith the pseudo-cationic complex.

Shape of curvesThe potential-volume E-V curves obtained are usually S-shapedand can be easily evaluated for the largest change in potential.Thus, the standard evaluation is selected in the titration method.If the curve shows a pronounced asymmetric profile, then theasymmetric evaluation can be used.

Practical Hints• SSEs are suitable for low concentrations (10-4 - 10-5 mol/L) in diluted solutions.• Caution: Organic solvents destroy the PVC-membrane!• After each sample clean the electrode thoroughly .• Conditioning of SSEs prior to titration is needed to achieve accurate and reproducible results.

Examples: - Dip the SSE in a standard solution of the surfactant to be titrated.- Perfom 2-3 titrations of the sample to be analysed before starting a series.

• Choose the appropriate electrolyte to avoid interferences. For instance, replace KCl with 2 M NaNO3

when using NaTPB for the titration of nonionic surfactant, since the potassium cation K+ forms a complexwith TPB- anions.

• Conditioning is sometimes needed for the reference electrode due to diffusion of the sample into the electrodethrough the ceramic diaphragm. If necessary, replace the electrolyte.

• Extreme pH-values, e.g. below pH 1-2, can damage the membrane of the surfactant sensitive electrode.

membrane



Titer of Hyamine 0.004 mol/L by potentiometric titration

Instruments: METTLER TOLEDO DL58METTLER TOLEDO AT261METTLER TOLEDO ST20APrinter

Method: 13

Accessories: Titration beaker 101974

Indication: 1. Surfactant sensitive electrode (e.g. DS500, ME-51107670)2. InLab 301 (3 mol/L KCl)

Sample: SDS, 5 mLc(SDS) = 0.004 mol/L

Compound: Sodium dodecylsulphate (SDS)M = 288.38 g/mol, z = 1

Preparation: 50 mL deionized water


Results: METTLER TOLEDO DL58 Titrator V2.0 Application Laboratory002

Method 13 Titer Hyamine 0.004 mol/L 02-Jun-1997 15:29 Measured 02-Jun-1997 16:11 User rd

ALL RESULTS



STATISTICS Number results R1 n = 5 Mean value x = 0.9967 Titer Hyamine Standard deviation s = 0.00758 Titer Hyamine Rel. standard deviation srel = 0.761 % Sample No. 1 deleted



Comments on method

• After each titration the surfactant electrodeand the reference electrode are dipped in aconditioning beaker with water to clean themthoroughly.

• Problems arising from small irregularities ofthe titration curve, from air bubbles or othersources can be avoided by setting anappropriate threshold value. In this way,incorrect evaluations can be avoided.

• A sample changer ST20A can be used for afully automatic analysis procedure: Enter«ST20A» as titration stand in the function«Sample».

• The auxiliary value H1 indicates theconcentration of the standard solution for titerdetermination ( c(SDS) = 0.004 mol/L).

Remarks

• The colloidal precipitate can coat the ceramicdiaphragm of the reference electrode and thus,thorough cleaning is necessary.

Waste disposal


Author: D. Rehwald

E – V curve

Method Method 13 Titer Hyamine 0.004 mol/L

Version 02-Jun-1997 15:29

Title Method ID . . . . . . . . . . . . . 13 Title . . . . . . . . . . . . . . . Titer Hyamine 0.004 mol/L Date/time . . . . . . . . . . . . . 02-Jun-1997 15:29 Sample Sample ID . . . . . . . . . . . . . SDS Entry type . . . . . . . . . . . . . Fixed volume Volume [mL] . . . . . . . . . . . 5.0 Molar mass M . . . . . . . . . . . . 288.38 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . ST20A Pump . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 50.0 Stir . . . . . . . . . . . . . Yes Pump . . . . . . . . . . . . . . No Rinse . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 30.0 Conditioning . . . . . . . . . . Yes Time [s] . . . . . . . . . . . 10 Interval . . . . . . . . . . 1 Rinse . . . . . . . . . . . . No

Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 30 Time [s] . . . . . . . . . . . . . . 90 EQP titration Titrant/Sensor Titrant . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . 0.004 Sensor . . . . . . . . . . . . . SSE Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . to volume Volume [mL] . . . . . . . . . . . 4 Wait time . . . . . . . . . . . . 3 Titrant addition . . . . . . . . . . Incremental ∆V [mL] . . . . . . . . . . . . . 0.05 Measure mode . . . . . . . . . . . . Equilibrium controlled ∆E [mV] . . . . . . . . . . . . . 1.0 ∆t [s] . . . . . . . . . . . . . 2.0 t(min) [s] . . . . . . . . . . . 5.0 t(max) [s] . . . . . . . . . . . 20.0 Recognition Threshold . . . . . . . . . . . . 100.0 Steepest jump only . . . . . . . No Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Positive Termination at maximum volume [mL] . . . . . 6.0 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . No comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition = . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=m/(VEQ*c*C) Constant . . . . . . . . . . . . . . C=1/(H1*z) Decimal places . . . . . . . . . . . 4 Result unit . . . . . . . . . . . . Result name . . . . . . . . . . . . Titer Hyamine Statistics . . . . . . . . . . . . . Yes

Titer Titrant . . . . . . . . . . . . . . Hyamine Concentration [moL/L]. . . . . . . . 0.004

Formula t = . . . . . . . . . . . . x Report Output unit . . . . . . . . . . . . Printer Results . . . . . . . . . . . . . . No All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . Yes Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - V curve . . . . . . . . . . No ∆

2E/ ∆V

2 - V curve . . . . . . . . . No


∆V/ ∆t - t curve . . . . . . . . . . No

Method 13 also runs with the following titrators:DL50, DL53, DL55DL67, DL70ES, DL77

Other titrators



Titer of SDS 0.004 mol/L by potentiometric titration


Method: 23


Indication: 1. Surfactant sensitive electrode (e.g. DS500, ME-51107670)2. InLab 301 ( 3 mol/L KCl)

Sample: CPC, 5 mLc(CPC) = 0.004 mol/L

Compound: CPC • 1 H2O

Cetylpyridinium chloridemonohydrateM = 358.01g/mol, z = 1


Titrant: SDS, c(SDS) = 0.004 mol/L

Results: METTLER TOLEDO DL58 Titrator V2.0 Application Laboratory002

Method 23 Titer SDS 0.004 mol/L 06-Jun-1997 12:04 Measured 06-Jun-1997 15:17 User C. De Caro

ALL RESULTS


1 SDS 5.0 mL R1 = 1.0163 Titer SDS 2 SDS 5.0 mL R1 = 1.0152 Titer SDS 3 SDS 5.0 mL R1 = 1.0089 Titer SDS 4 SDS 5.0 mL R1 = 1.0057 Titer SDS 5 SDS 5.0 mL R1 = 1.0133 Titer SDS 6 SDS 5.0 mL R1 = 1.0173 Titer SDS

STATISTICS Number results R1 n = 6 Mean value x = 1.0128 Titer SDS Standard deviation s = 0.00456 Titer SDS Rel. standard deviation srel = 0.450 %

TITER Titrant SDS 0.004 mol/L New titer t = 1.0128


Comments on method

• After each titration the surfactant electrodeand the reference electrode are dipped in aconditioning beaker with water to clean themthoroughly.


• The precipitate can coat the ceramicdiaphragm of the reference electrode and thus,thorough cleaning is necessary.

• Auxiliary value H1 indicates theconcentration of the standard solution for titerdetermination ( c(CPC) = 0.004 mol/L).

Waste disposal


Method

E – V curve

Other titratorsMethod 13 also runs with the following titrators:DL50, DLDL53, DL55DL67, DL70ES, DL77

Author: C. De Caro

Method 23 Titer SDS 0.004 mol/L Version 06-Jun-1997 12:04

Title Method ID . . . . . . . . . . . . . 23 Title . . . . . . . . . . . . . . . Titer SDS 0.004 mol/L Date/time . . . . . . . . . . . . . 06-Jun-1997 12:04 Sample Sample ID . . . . . . . . . . . . . CPC Entry type . . . . . . . . . . . . . Fixed volume Volume [mL] . . . . . . . . . . . 5.0 Molar mass M . . . . . . . . . . . . 358.01 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . ST20A Pump . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 60.0 Stir . . . . . . . . . . . . . No Pump . . . . . . . . . . . . . . No Rinse . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 20.0 Conditioning . . . . . . . . . . Yes Time [s] . . . . . . . . . . . 60 Interval . . . . . . . . . . 1 Rinse . . . . . . . . . . . . No

Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 30 Time [s] . . . . . . . . . . . . . . 90 EQP titration Titrant/Sensor Titrant . . . . . . . . . . . . . SDS Concentration [mol/L] . . . . . . 0.004 Sensor . . . . . . . . . . . . . SSE Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . to volume Volume [mL] . . . . . . . . . . . 3.5 Wait time . . . . . . . . . . . . 30 Titrant addition . . . . . . . . . . Dynamic ∆E(set)[mV] . . . . . . . . . . . 8.0 ∆V(min) [mL] . . . . . . . . . . 0.02 ∆V(max) [mL] . . . . . . . . . . 0.2 Measure mode . . . . . . . . . . . . Equilibrium controlled ∆E [mV] . . . . . . . . . . . . . 1.0 ∆t [s] . . . . . . . . . . . . . 2.0 t(min) [s] . . . . . . . . . . . 5.0 t(max) [s] . . . . . . . . . . . 20.0 Recognition Threshold . . . . . . . . . . . . 500.0 Steepest jump only . . . . . . . Yes Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Positive Termination at maximum volume [mL] . . . . . 6.0 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . No comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition = . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=m/(VEQ*c*C) Constant . . . . . . . . . . . . . . C=1/(H1*z) Decimal places . . . . . . . . . . . 4 Result unit . . . . . . . . . . . . Result name . . . . . . . . . . . . Titer SDS Statistics . . . . . . . . . . . . . Yes

Titer Titrant . . . . . . . . . . . . . . SDS Concentration [moL/L]. . . . . . . . 0.004

Formula t = . . . . . . . . . . . . x Report Output unit . . . . . . . . . . . . Printer Results . . . . . . . . . . . . . . No All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . Yes Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - V curve . . . . . . . . . . Yes ∆

2E/ ∆V

2 - V curve . . . . . . . . . No


∆V/ ∆t - t curve . . . . . . . . . . No


ET1 0.0000 377.4 0:05 2.0000 2.0000 360.4 -17.1 -8.5 0:16 3.0000 1.0000 348.5 -11.9 -11.9 0:25 ET2 3.5000 0.5000 340.9 -7.6 -15.1 0:59 3.7000 0.2000 336.9 -4.1 -20.4 1:06 3.9000 0.2000 333.0 -3.9 -19.4 1:12 4.1000 0.2000 327.9 -5.0 -25.2 1:19 4.3000 0.2000 321.4 -6.6 -33.0 1.27 4.4960 0.1960 313.9 -7.5 -38.2 1:34 4.6790 0.1830 304.2 -9.6 -52.6 1:43 4.7980 0.1190 294.9 -9.3 -78.2 1:52 4.8750 0.0770 278.4 -16.5 -214.0 2:13 4.8970 0.0220 265.3 -13.1 -596.3 2:33 4.9170 0.0200 248.4 -16.9 -846.5 2:53EQP1 4.9370 0.0200 229.9 -18.5 -924.1 3:14 4.9570 0.0200 212.3 -17.6 -878.8 3:34 4.9770 0.0200 204.5 -7.9 -394.2 3:46 4.9970 0.0200 197.2 -7.3 -365.1 3:57 5.0200 0.0230 192.8 -4.4 -191.0 4:04 5.0660 0.0460 184.9 -7.9 -171.4 4:12 5.1180 0.0520 178.2 -6.7 -129.2 4:18 5.2090 0.0910 169.8 -8.3 -91.6 4:26 5.3570 0.1480 160.5 -9.3 -62.9 4:33 5.5570 0.2000 152.1 -8.4 -42.0 4:40 5.7570 0.2000 146.0 -6.1 -30.7 4:46 5.9570 0.2000 141.2 -4.8 -23.9 4:52 6.0000 0.0430 140.4 -0.8 -18.0 4.57



Titer of sodium tetraphenylborate by potentiometric titration

Instruments: METTLER TOLEDO DL58METTLER TOLEDO AT261METTLER TOLEDO ST20AHP Printer

Method: 71007


Indication: 1. Surfactant sensitive electrode (e.g. DS500, ME-51107670)2. InLab 301 (2 M NaNO

3)

Sample: AgNO3 , 5 mL

c(AgNO3) = 0.002 mol/L

Compound: Silver nitrate, AgNO3

M = 169.88 g/mol, z = 1

Preparation: 40 mL pH 4.75 Buffer(Acetate buffer)

Titrant: Na-Tetraphenylborate (NaTPB)c(NaTPB) = 0.004 mol/L ,pH 9-10

Results: Method 71007 Titer NaTPB 0.004mol/L 07-Nov-1997 16:14 Measured 08-Nov-1997 16:51 User P. Maurer

ALL RESULTS


1 AgNO3 5.0 mL

R1 = 0.90224 Titer NaTPB 2 AgNO

3 5.0 mL


3 5.0 mL


3 5.0 mL


3 5.0 mL


3 5.0 mL


3 5.0 mL


3 5.0 mL

R1 = 0.88365 Titer NaTPB

STATISTICS Number results R1 n = 7 Mean value x = 0.91070 Titer NaTPB Standard deviation s = 0.00610 Titer NaTPB Rel. standard deviation srel = 0.669 % Sample No. 8 deleted

TITER Titrant NaTPB 0.004 mol/L New titer t = 0.90732


Comments on method

• After each titration the surfactant electrode andthe reference electrode are dipped in aconditioning beaker containing acetate buffer toclean them thoroughly (see function «Sample»).

• Acetate buffer 0.01 mol/L:1.0255 g sodium acetate are added to 125 mL0.1 mol/L acetic acid in a 250 mL volumetricflask. The buffer concentration is 0.1 mol/L.50 mL of the 0.1 mol/L acetate buffer are dilutedwith deionized water in a 500 mL flask to obtainthe desired concentration of 0.01 mol/L.

• Na-TPB Titrant:Adjust the pH to 9-10 with sodium hydroxidesolution [see lit. 3].

• H1 gives the concentration of the standardsolution of AgNO

3 used for the titer determination,

i.e., H1 = 0.002 mol/L.

Waste disposal

Filtration:- The precipitate (silver chloride) has to be classifiedas special waste.- The filtrate has to be neutralized with NaOH beforefinal disposal.

Method

E – V curve

Other titratorsMethod 71007 also runs with the following titrators:DL50, DLDL53, DL55DL67, DL70ES, DL77

Author: P. Maurer

Method 71007 Titer NaTPB 0.004mol/L Version 07-Nov-1997 16:14

Title Method ID . . . . . . . . . . . . . 71007 Title . . . . . . . . . . . . . . . Titer NaTPB 0.004mol/L Date/time . . . . . . . . . . . . . 07-Nov-1997 16:14 Sample Sample ID . . . . . . . . . . . . . AgNO3 Entry type . . . . . . . . . . . . . Fixed volume Volume [mL] . . . . . . . . . . . 5.0 Molar mass M . . . . . . . . . . . . 169.88 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . ST20A Pump . . . . . . . . . . . . . . No Pump . . . . . . . . . . . . . . No Rinse . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 30.0 Conditioning . . . . . . . . . . Yes Time [s] . . . . . . . . . . . 90 Interval . . . . . . . . . . 1 Rinse . . . . . . . . . . . . Yes Solvent . . . . . . . . . . H 2O Volume [mL] . . . . . . . . 10.0

Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 30 EQP titration Titrant/Sensor Titrant . . . . . . . . . . . . . NaTPB Concentration [mol/L] . . . . . . 0.004 Sensor . . . . . . . . . . . . . SSE Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . No Titrant addition . . . . . . . . . . Dynamic ∆E(set)[mV] . . . . . . . . . . . 8.0 ∆V(min) [mL] . . . . . . . . . . 0.02 ∆V(max) [mL] . . . . . . . . . . 0.2 Measure mode . . . . . . . . . . . . Equilibrium controlled ∆E [mV] . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . 1.0 t(min) [s] . . . . . . . . . . . 3.0 t(max) [s] . . . . . . . . . . . 45.0 Recognition Threshold . . . . . . . . . . . . 800 Steepest jump only . . . . . . . Yes Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Negative Termination at maximum volume [mL] . . . . . 4.0 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . No comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition = . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=m/(VEQ*c*C) Constant . . . . . . . . . . . . . . C=1/(H1*z) Decimal places . . . . . . . . . . . 5 Result unit . . . . . . . . . . . . Result name . . . . . . . . . . . . Titer NaTPB Statistics . . . . . . . . . . . . . Yes

Titer Titrant . . . . . . . . . . . . . . NaTPB Concentration [moL/L]. . . . . . . . 0.004

Formula t = . . . . . . . . . . . . x Report Output unit . . . . . . . . . . . . Printer Results . . . . . . . . . . . . . . No All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . Yes Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - V curve . . . . . . . . . . Yes ∆

2E/ ∆V

2 - V curve . . . . . . . . . No


∆V/ ∆t - t curve . . . . . . . . . . No


ET1 0.0000 237.8 0:03 0.0200 0.0200 237.2 -0.6 -32.3 0:06 0.0400 0.0200 236.4 -0.7 -35.5 0:10 0.0800 0.0400 235.6 -0.8 -21.0 0:13 1.6000 0.0800 234.7 -0.9 -11.3 0:17 0.3200 0.1600 233.3 -1.4 -8.5 0:20 0.5200 0.2000 231.1 -2.2 -11.0 0:25

2.6830 0.0200 111.7 -13.6 -678.5 3:19 2.7030 0.0200 105.3 -6.4 -319.9 3:32 2.7230 0.0200 78.0 -27.3 -1366.7 4:18 2.7430 0.0200 35.2 -42.8 -2138.9 5:03EQP1 2.7630 0.0200 -12.3 -47.6 -2378.0 5:49 2.7830 0.0200 -37.9 -25.6 -1279.5 6:26 2.8270 0.0440 -56.0 -18.0 -409.8 6:54 2.8470 0.0200 -60.4 -4.4 -219.7 7:03

3.7040 0.2000 -112.9 -5.6 -27.8 8:31 3.9040 0.2000 -117.1 -4.2 -21.0 8:40 4.0000 0.0960 -119.0 -1.9 -19.5 8:44



Potentiometric titration of anionic surfactants in liquid detergents


Method: 702


Indication: 1. Surfactant sensitive electrode (e.g. DS500, ME-51107670)2. InLab 301 (3 mol/L KCl)

Sample: Liquid detergents(5 g in 500 mL)10 mL aliquot





Results: Method 702 Tenside/Anionische 02-Apr-1997 8:50 Measured 02-Apr-1997 9:20 User rd

ALL RESULTS


1 Liq. Det. 1 5.0621 g R1 = 9.142 mmol/L Tensid R2 = 17.689 % AT mittl.M=387 2 Liq. Det. 1 5.0621 g R1 = 8.967 mmol/L Tensid R2 = 17.350 % AT mittl.M=387 3 Liq. Det. 1 5.0621 g R1 = 8.915 mmol/L Tensid R2 = 17.250 % AT mittl.M=387 4 Liq. Det. 1 5.0621 g R1 = 9.046 mmol/L Tensid R2 = 17.504 % AT mittl.M=387 5 Liq. Det. 1 5.0621 g R1 = 8.189 mmol/L Tensid R2 = 15.845 % AT mittl.M=387

STATISTICS Number results R1 n = 4 Mean value x = 9.017 mmol/L Tensid Standard deviation s = 0.09887 mmol/L Tensid Rel. standard deviation srel = 1.096 % Sample No. 5 deleted

STATISTICS Number results R2 n = 4 Mean value x = 17.448 % AT mittl.M=387 Standard deviation s = 0.19131 % AT mittl.M=387 Rel. standard deviation srel = 1.096 % Sample No. 5 deleted


Comments on method

• After each titration the surfactant electrodeand the reference electrode are cleaned withabundant water.


• It is recommended to use an InLab 301reference electrode to avoid problems with thesleeve.

• Addition of 20-50 mL methanol to the stocksolution of the different liquid detergents(stock solution: 5 g in a 500 mL flask, dilutedwith water) decreases foaming of the solution.

Caution: Do not add more than 20-50 mLmethanol to the stock solution since organicsolvents damage the membrane of thesurfactant electrode.

Method 702 Tenside/Anionische Version 02-Apr-1997 8:50

Title Method ID . . . . . . . . . . . . . 702 Title . . . . . . . . . . . . . . . Tenside/Anionische Date/time . . . . . . . . . . . . . 02-Apr-1997 8:50 Sample Sample ID . . . . . . . . . . . . . Liq. Det. 1 Entry type . . . . . . . . . . . . . Weight Lower limit [g] . . . . . . . . . 4.0 Upper limit [g] . . . . . . . . . 6.0 Molar mass M . . . . . . . . . . . . 387 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . Stand 1

Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 40 Time [s] . . . . . . . . . . . . . . 120 EQP titration Titrant/Sensor Titrant . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . 0.01 Sensor . . . . . . . . . . . . . SSE Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . No Titrant addition . . . . . . . . . . Dynamic ∆E(soll) [mV] . . . . . . . . . . 6.0 ∆V(min) [mL] . . . . . . . . . . 0.005 ∆V(max) [mL] . . . . . . . . . . 0.1 Measure mode . . . . . . . . . . . . Equilibrium controlled ∆E [mV] . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . 1.0 t(min) [s] . . . . . . . . . . . 5.0 t(max) [s] . . . . . . . . . . . 30.0 Recognition Threshold . . . . . . . . . . . . 100.0 Steepest jump only . . . . . . . No Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Positive Termination at maximum volume [mL] . . . . . 7.0 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . No comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition = . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=Q*C/m Constant . . . . . . . . . . . . . . C=1000 Decimal places . . . . . . . . . . . 3 Result unit . . . . . . . . . . . . mmol/L Result name . . . . . . . . . . . . Tensid Statistics . . . . . . . . . . . . . Yes Calculation Formula . . . . . . . . . . . . . . R2=(Q*C2)/(m*10/500) Constant . . . . . . . . . . . . . . C2=M/(10*z) Decimal places . . . . . . . . . . . 3 Result unit . . . . . . . . . . . . % AT Result name . . . . . . . . . . . . mittl.M=387 Statistics . . . . . . . . . . . . . Yes Report Output unit . . . . . . . . . . . . Printer Results . . . . . . . . . . . . . . Yes All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . No Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - V curve . . . . . . . . . . No ∆

2E/ ∆V

2 - V curve . . . . . . . . . No


∆V/ ∆t - t curve . . . . . . . . . . No

E – V curve

Method

Other titrators


Waste disposal


Author: D. Rehwald, C. De Caro, P. Maurer



Component content, % value, % samples % %

Liquid detergent 1 18.0 17.1 6 17.27 0.639 Method: 702

Average molar mass: 387 pH 3 pH 3 INC: 0.1 mL

Fatty alcohol ether sulphate 10.0 Threshold: 100

Secondary alkanesulphonate 6.0Cocoamidopropylbetaine 2.0

Conc. liquid detergent 2 38.5 32.8 6 34.13 0.401 Predispensing: 5 mL

Average molar mass: 362 pH 3 pH 3 Wait time: 30 s

Fatty alcohol ether sulphate 11.0 DYN: 10 mV, 0.005-0.2 mL

Secondary alkanesulphonate 20.0 EQU: 0.5/1 mV/s, 5-30 s

Cocoamidopropylbetaine 3.5 Threshold: 100

Nonionic surfactant (7 EO, M=520) 4.0 Maximum volume: 12 mL

Liquid detergent 3 33.0 - 6 33.85 1.23 Stir: 50%, 30s

Anionic surfactant A (M=346) 27.0 (n) c(CPC) = 0.004 mol/L

Anionic surfactant B (M=385) 6.0 INC: 0.25 mL, TFIX: 8 s--> Average: 353.09 Thresh.: 60, max vol: 6 mL

Liquid detergent 4Anionic surfactant as SDS 15-30.0 14.18 10 15.25 0.951 c(Hyamine)=0.004 mol/L

(M=288.38) pH 1-2 (n) Stir:50%, 60s, Predisp.: 5mL,

Wait time: 30 s , DYN: 6 mV,0.1-0.5 mL, EQU 0.25/1 mV/s,

2-20 s, Threshold: 50

Nominal value: Theoretical composition of the sample as total washing active matter. It is obtainedby summing the percentages of all surfactant components in the sample.

Reference: Value given by the producer and mostly based on classical two-phase titration. Itindicates the total washing active matter.


Results

Additional samples

Sample Number of Concentration Recovery RSDsamples mol/L % %

Standard solution 1CPC, c = 0.004 mol/L 6 0.0040 100.62 0.728

Standard solution 2SDS, c = 0.004 mol/L 6 0.0040 99.95 0.746





Potentiometric titration of nonionic surfactants in raw materials


Methods: 33 f (calibration factor)33 g (content determination)


Indication: 1. Surfactant sensitive electrode (e.g. DS500, ME-51107670)2. InLab 301 reference electrode (2 M NaNO3)

Sample: Raw materials (10 g in 1 L)5 mL aliquot

Compound: Nonionic surfactants(fatty alcohol C10/C14-6 EO)

Preparation: - 10 mL BaCl2 0.1 mol/L

- 5 mL PVA solution- Deion. water to 50 mL

Titrant: Na-tetraphenylborate (NaTPB)c(NaTPB)=0.0203 mol/L, pH 9-10

Standard: Triton N101C

9H

19-C

6H

4-(OCH

2CH

2)

x-OH

x= 9-10Average M: 636.86, z=1

Results Calibration factor, method 33 f / Calibration with Triton N101METTLER TOLEDO DL58 Titrator V2.0 Mettler-Toledo GmbH 002 Market Support Laboratory

Method 33 f Factor NioT 04-Jun-1997 12:10 Measured 04-Jun-1997 12:56 User rd

ALL RESULTS


1 TritonN101 5.0 mL R1 = 8.48712 mg/mL Factor 2 TritonN101 5.0 mL R1 = 8.67061 mg/mL Factor 3 TritonN101 5.0 mL R1 = 8.78171 mg/mL Factor 4 TritonN101 5.0 mL R1 = 8.97446 mg/mL Factor 5 TritonN101 5.0 mL R1 = 9.00326 mg/mL Factor 6 TritonN101 5.0 mL R1 = 8.86509 mg/mL Factor

STATISTICS Number results R1 n = 6 Mean value x = 8.79704 mg/mL Factor Standard deviation s = 0.19540 mg/mL Factor Rel. standard deviation srel = 2.221 %

AUXILIARY VALUE New value H3 = 8.79704 Factor NioT


Method 33 f (calibration factor)

Other titratorsMethod 33 f also runs with the following titrators:DL50, DL53, DL55DL67, DL70ES, DL77

Method 33 f Factor NioT Version 04-Jun-1997 12:10

Title Method ID . . . . . . . . . . . . . 33 f Title . . . . . . . . . . . . . . . Factor NioT Date/time . . . . . . . . . . . . . 04-Jun-1997 12:10 Sample Sample ID . . . . . . . . . . . . . TritonN101 Entry type . . . . . . . . . . . . . Fixed volume ∆V [mL] . . . . . . . . . . . . . 5.0 Molar mass M . . . . . . . . . . . . 1 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . Stand 1 Pump . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 35.0 Stir . . . . . . . . . . . . . No Pump . . . . . . . . . . . . . . No Rinse . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 30.0 Conditioning . . . . . . . . . . Yes Time [s] . . . . . . . . . . . 60 Interval . . . . . . . . . . 1 Rinse . . . . . . . . . . . . Yes Solvent . . . . . . . . . . H 2O Volume [mL] . . . . . . . . 10.0

Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 35 Time [s] . . . . . . . . . . . . . . 90 EQP titration Titrant/Sensor Titrant . . . . . . . . . . . . . NaTPB Concentration [mol/L] . . . . . . 0.0203 Sensor . . . . . . . . . . . . . SSE Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . No Titrant addition . . . . . . . . . . Dynamic

∆E (set). . . . . . . . . . . . . 6.0 ∆V (min) [mL] . . . . . . . . . . 0.015 ∆V (max) [mL] . . . . . . . . . . 0.15 Measure mode . . . . . . . . . . . . Equilibrium controlled

∆E (set). . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . 1.0 t(min) [mL] . . . . . . . . . . . 3.0 t(max) [s] . . . . . . . . . . . 30.0 Recognition Threshold . . . . . . . . . . . . 500.0 Steepest jump only . . . . . . . No Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Negative Termination at maximum volume [mL] . . . . . 5.0 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . No comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition = . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=C*m/VEQ Constant . . . . . . . . . . . . . . C=2.55157 Decimal places . . . . . . . . . . . 5 Result unit . . . . . . . . . . . . mg/mL Result name . . . . . . . . . . . . Factor Statistics . . . . . . . . . . . . . Yes Auxiliary value ID . . . . . . . . . . . . . . . . . Factor NioT Formula . . . . . . . . . . . . . . H3= x Report Output unit . . . . . . . . . . . . Printer Results . . . . . . . . . . . . . . Yes All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . No Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - V curve . . . . . . . . . . No ∆

2E/ ∆V

2 - V curve . . . . . . . . . No


∆V/ ∆t - t curve . . . . . . . . . . No

Principle

• Since the titration reaction is not stoichiometricthe content determination of nonionic surfactantsis based on a comparative titration .

• A sample of known concentration is titratedaccording to method 33 f. From the titrantconsumption VEQ and the known concentration,a factor R is determined and stored as auxiliaryvalue H3. This is taken into account in the titration33 g for the sample content determination (seenext page).

Comments on method 33 f

• Na-TPB titrant:Adjust the pH to 9-10 with sodium hydroxidesolution [see lit. 3].

• Polyvinyl alcohol (PVA) solution:Dissolve 3-4 g PVA in ca. 250 mL water bywarming the solution, and allow it to cool downbefore addition.

• C is the concentration of the standard solution, inthis case C=2.55157 g/L

• A long conditioning time (60 s) ensures anefficient cleaning of the electrode.

E – V curve


ET1 0.0000 121.6 0:03 0.0150 0.0150 121.5 -0.1 -4.3 0:06 0.0300 0.0150 121.4 -0.1 -4.3 0:10 0.0600 0.0300 121.2 -0.2 -6.5 0:13 0.1200 0.0060 121.0 -0.3 -4.3 0:17 0.2400 0.1200 120.3 -0.7 -5.9 0:20 0.3900 0.1500 119.1 -1.2 -7.8 0:24 0.5400 0.1500 117.5 -1.6 -10.3 0:28 0.6900 0.1500 114.3 -3.2 -21.3 0:33 0.8400 0.1500 109.1 -5.2 -34.5 0:41 0.9660 0.1260 104.7 -4.5 -35.4 0:47 1.1160 0.1500 99.5 -5.2 -34.9 0:54 1.2660 0.1500 92.4 -7.0 -47.0 1:02 1.3670 0.1010 81.6 -10.9 -107.5 1:16 1.4020 0.0350 75.2 -6.3 -180.9 5:30 1.4250 0.0230 66.9 -8.3 -362.4 1:37 EQP1 1.4400 0.0150 58.3 -8.6 -573.0 1:51 1.4550 0.0150 50.9 -7.4 -495.4 2:02 1.4700 0.0150 42.8 -8.1 -538.5 2:14

4.7010 0.1500 -107.7.9 -1.4 -9.0 5:35 4.8510 0.1500 -109.0 -1.3 -8.6 5:39

5.0000 0.1490 -110.1 -1.2 -7.8 5:43



Method 33 g Content NioT Version 05-Jun-1997 9:09

Title Method ID . . . . . . . . . . . . . 33 g Title . . . . . . . . . . . . . . . Content NioT Date/time . . . . . . . . . . . . . 05-Jun-1997 9:09 Sample Sample ID . . . . . . . . . . . . . Nio Sample A Entry type . . . . . . . . . . . . . Fixed volume ∆V [mL] . . . . . . . . . . . . . 5.0 Molar mass M . . . . . . . . . . . . 1 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . ST20A Pump . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 35.0 Stir . . . . . . . . . . . . . No Pump . . . . . . . . . . . . . . No Rinse . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 30.0 Conditioning . . . . . . . . . . Yes Time [s] . . . . . . . . . . . 60 Interval . . . . . . . . . . 1 Rinse . . . . . . . . . . . . Yes Solvent . . . . . . . . . . H 2O Volume [mL] . . . . . . . . 10.0

Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 35 Time [s] . . . . . . . . . . . . . . 90 EQP titration Titrant/Sensor Titrant . . . . . . . . . . . . . NaTPB Concentration [mol/L] . . . . . . 0.0203 Sensor . . . . . . . . . . . . . SSE Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . No Titrant addition . . . . . . . . . . Dynamic

∆E (set). . . . . . . . . . . . . 6.0 ∆V (min) [mL] . . . . . . . . . . 0.035 ∆V (max) [mL] . . . . . . . . . . 0.15 Measure mode . . . . . . . . . . . . Equilibrium controlled

∆E (set). . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . 1.0 t(min) [mL] . . . . . . . . . . . 4.0 t(max) [s] . . . . . . . . . . . 30.0 Recognition Threshold . . . . . . . . . . . . 45.0 Steepest jump only . . . . . . . Yes Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Negative Termination at maximum volume [mL] . . . . . 6.5 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . No comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition = . . . . . . . . . neq=0 Calculation Formula . . . . . . . . . . . . . . R=VEQ Constant . . . . . . . . . . . . . . Decimal places . . . . . . . . . . . 5 Result unit . . . . . . . . . . . . mL Result name . . . . . . . . . . . . Cons. TM Statistics . . . . . . . . . . . . . No Calculation Formula . . . . . . . . . . . . . . R2=(H3*R1*100)/50 Constant . . . . . . . . . . . . . . Decimal places . . . . . . . . . . . 3 Result unit . . . . . . . . . . . . % Result name . . . . . . . . . . . . Content Statistics . . . . . . . . . . . . . Yes Report Output unit . . . . . . . . . . . . Printer+Memory card Results . . . . . . . . . . . . . . Yes All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . Yes Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - V curve . . . . . . . . . . No ∆

2E/ ∆V

2 - V curve . . . . . . . . . No


∆V/ ∆t - t curve . . . . . . . . . . No

E – V curve

Method 33 g (content determination)


ET1 0.0000 106.8 0:04 0.0350 0.0350 106.8 0.0 0.0 0:08 0.0700 0.0350 106.8 0.0 0.0 0:13 0.1400 0.0700 106.8 -0.1 -0.9 0:17 0.2800 0.1400 106.6 -0.2 -1.4 0:22 0.4300 0.1500 106.3 -0.3 -1.7 0:26 0.5800 0.1500 106.0 -0.3 -2.2 0:31 0.7300 0.1500 105.6 -0.4 -2.6 0:36 0.8800 0.1500 105.3 -0.3 -2.2 0:40 1.0300 0.1500 104.8 -0.5 -3.0 0:45 1.1800 0.1500 104.4 -0.5 -3.0 0:50 1.3300 0.1500 103.9 -0.5 -3.0 0:54 1.4800 0.1500 103.4 -0.5 -3.4 0:59 1.6300 0.1500 102.7 -0.6 -4.3 1:04

4.4800 0.1500 69.3 -4.1 -27.1 2:39 4.6300 0.1500 64.8 -4.6 -30.6 2:46 4.7800 0.1500 59.4 -5.4 -35.8 2:53 4.9260 0.1460 53.3 -6.1 -41.6 3:02 5.0520 0.1260 47.1 -6.2 -49.2 3:11 5.1570 0.1050 41.9 -5.2 -49.2 3:20 5.2780 0.1210 36.3 -5.6 -46.5 3:28 5.4150 0.1370 28.8 -7.5 -54.7 3:39 EQP1 5.5100 0.0950 23.6 -5.2 -55.1 3:47 5.6180 0.1080 17.7 -5.9 -54.4 3:56 5.7290 0.1110 12.0 -5.7 -51.2 4:04 5.8530 0.1240 5.8 -6.3 -50.3 4:14 5.9730 0.1200 0.6 -5.1 -42.5 4:21 6.1230 0.1500 -5.6 -6.3 -41.8 4:29 6.2690 0.1460 -10.5 -4.9 -33.6 4:35 6.4190 0.1500 -16.6 -6.1 -40.5 4:44 6.5000 0.0810 -19.5 -2.9 -35.9 4:50

Comments on method 33 g

• Na-TPB titrant:Adjust the pH to 9-10 with sodium hydroxidesolution [see lit. 3].

• To obtain the content value in %, the consumptionmust be:1. multiplied by the calibration factor, stored as

H3,2. and then divided by the sample size m.

• R2 gives the non-ionic surfactant content of theraw material of the sample expressed as TritonN101 (see method 33 f).

Author: D. Rehwald, C. De Caro


Other titratorsMethods 33 f and 33 g can also run with thefollowing titrators:DL50, DL53, DL55DL67, DL70ES, DL77


Results Content determination, Method 33 g / Titration of NIO Sample A

General remarks:

Principle• Samples of unkown composition are measured and compared against a reference nonionic surfactant, for

instance, nonylphenol ethoxylate with 10 EO (1 EO: CH2-CH

2-O ) or, if known, a pure solution of the

nonionic surfactant present in the sample.• Nonionic surfactants form a complex with barium cations Ba2+. The formed complex has a positive charge

-a pseudo-cationic surfactant. The analyte can be titrated with a bulky cation which is able to precipitatethe pseudo-cationic surfactant.Tetraphenylborate (TPB, (C

6H

5)4B- ) is used to form an insoluble complex with the pseudo-cationic surfactant.

The reaction is not stoichiometric, i.e., there is no well-defined ratio between the amounts of substance ofthe two species. Thus, a calibration titration with a standard solution of know concentration must beperformed in advance before the titration of the sample. Its result, a calibration factor, is then used in thecalculation of the sample titration.

Titration technique• Always take the same sample volume for both methods 33 f (factor) and 33 g (content). Choose the sample

volume to get a titrant consumption of about 5 mL.• Unknown sample:

First run a titration with termination at maximum volume to record the whole titration curve. In this way,the parameters and the evaluation procedure of the method can easily be optimized.


Method 33 g Content NioT 05-Jun-1997 9:09 Measured 05-Jun-1997 9:55 User rd

ALL RESULTS


1 Nio Sample A 5.0 mL R1 = 5.68601 mL Cons. TM R2 = 100.040 % Content 2 Nio Sample A 5.0 mL R1 = 5.46856 mL Cons. TM R2 = 96.214 % Content 3 Nio Sample A 5.0 mL R1 = 5.48065 mL Cons. TM R2 = 96.214 % Content 4 Nio Sample A 5.0 mL R1 = 5.58600 mL Cons. TM R2 = 98.281 % Content 5 Nio Sample A 5.0 mL R1 = 6.01352 mL Cons. TM R2 = 105.802 % Content 6 Nio Sample A 5.0 mL R1 = 5.68601 mL Cons. TM R2 = 96.347 % Content

STATISTICS Number results R2 n = 4 Mean value x = 96.852 % Content Standard deviation s = 0.84851 % Content Rel. standard deviation srel = 0.876 % Sample No. 1 deleted Sample No. 5 deleted



Potentiometric titration of a betaine in shampoo


Method: 61009


Indication: DG113 (LiCl in ethanol)c(LiCl)= 1 mol/L

Sample: Shampoo0.8-1 g / sample

Compound: Cocoamidopropylbetaine, ca. 4%

(amphoteric surfactant)M = 372 g/mol, z = 1

Preparation: ca. 1 g sample in beaker10 mL methanol50 mL acetone/isopropanol 4:1 v/v

3 mL HCl, c(HCl) = 0.5 mol/L

Titrant: KOH in methanolc(KOH) = 0.1 mol/L

Standard: Primary standardBenzoic acid in methanol

Results:

Method 61009 Betaine nonaq. solvent 27-Nov-1997 17:56 Measured 27-Nov-1997 19:05 User P. Maurer

ALL RESULTS


1 Cosmed 0.8688 g R1 = 4.027 % Content 2 Cosmed 0.9932 g R1 = 4.201 % Content 3 Cosmed 1.0078 g R1 = 4.287 % Content 4 Cosmed 0.8936 g R1 = 3.603 % Content 5 Cosmed 1.0348 g R1 = 4.236 % Content

STATISTICS Number results R1 n = 4 Mean value x = 4.188 % Content Standard deviation s = 0.11264 Content Rel. standard deviation srel = 2.690 % Sample No. 4 deleted

METTLER TOLEDO DL58 Titrator V2.0 Application Laboratory002


Comments on method

• According to Buschmann betaines can be titrateddirectly with a base in a strong acid solution [seeref. 10].

• Betaines are protonated by adding an excess ofHCl (Protonation of the carboxylic group,COOH). The protonated compound can be titratedwith a base, in a similar way as an acid/basetitration.

• Usually, formulated products and concentratedraw materials contain additional componentswhich can not be distinguished and therefore theyare titrated together.For this reason, a non-aqueous solvent is used todifferentiate the different components.

• This titration leads to three equivalence points:1. EQP1: Neutralization of excess HCl2. EQP2: Titration of betaine ⇒ Q23. EQP3: Additional components

• Due to the quite low threshold value anappropriate threshold must be selected for diffe-rent samples. Too low value leads to therecognition of fake equivalence points.

Waste disposalOrganic waste.

Method

E – V curve

Other titratorsMethod 61009 also runs with the followingtitrators:DL50, DL53, DL55DL67, DL70ES, DL77

Author: P. Maurer

Method 61009 Betaine nonaq. solvent Version 27-Nov-1997 17:56

Title Method ID . . . . . . . . . . . . . 61009 Title . . . . . . . . . . . . . . . Betaine nonaq. solvent Date/time . . . . . . . . . . . . . 27-Nov-1997 17:56 Sample Sample ID . . . . . . . . . . . . . Cosmed Entry type . . . . . . . . . . . . . Weight Lower limit [g] . . . . . . . . . 0.8 Volume [mL] . . . . . . . . . . . 1.2 Molar mass M . . . . . . . . . . . . 372 Equivalent number z . . . . . . . . 1 Titration stand . . . . . . . . . . ST20A Pump . . . . . . . . . . . . . . No Pump . . . . . . . . . . . . . . No Rinse . . . . . . . . . . . . . . Yes Solvent . . . . . . . . . . . H 2O Volume [mL] . . . . . . . . . 20.0 Conditioning . . . . . . . . . . No

Temperature sensor . . . . . . . . . Manual Stir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 30 EQP titration Titrant/Sensor Titrant . . . . . . . . . . . . . KOH in MeOH Concentration [mol/L] . . . . . . 0.1 Sensor . . . . . . . . . . . . . DG113 Unit of meas. . . . . . . . . . . mV Predispensing . . . . . . . . . . . to volume Volume [mL] . . . . . . . . . . . 5 Wait time . . . . . . . . . . . . 0 Titrant addition . . . . . . . . . . Dynamic ∆E(set)[mV] . . . . . . . . . . . 8.0 ∆V(min) [mL] . . . . . . . . . . 0.03 ∆V(max) [mL] . . . . . . . . . . 0.3 Measure mode . . . . . . . . . . . . Equilibrium controlled ∆E [mV] . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . 1.0 t(min) [s] . . . . . . . . . . . 3.0 t(max) [s] . . . . . . . . . . . 30.0 Recognition Threshold . . . . . . . . . . . . 70.0 Steepest jump only . . . . . . . No Range . . . . . . . . . . . . . . No Tendency . . . . . . . . . . . . Negative Termination at maximum volume [mL] . . . . . 20.0 at potential . . . . . . . . . . No at slope . . . . . . . . . . . . No after number EQPs . . . . . . . . No comb. termination conditions . . No Evaluation Procedure . . . . . . . . . . . . Standard Potential 1 . . . . . . . . . . . No Potential 2 . . . . . . . . . . . No Stop for reevaluation . . . . . . Yes Condition = . . . . . . . . . neq<3 Calculation Formula . . . . . . . . . . . . . . R=Q2*C/m Constant . . . . . . . . . . . . . . C=M/(10*z) Decimal places . . . . . . . . . . . 3 Result unit . . . . . . . . . . . . % Result name . . . . . . . . . . . . Content Statistics . . . . . . . . . . . . . Yes Report Output unit . . . . . . . . . . . . Printer Results . . . . . . . . . . . . . . Yes All results . . . . . . . . . . . . Yes Raw results . . . . . . . . . . . . No Table of measured values . . . . . . Yes Sample data . . . . . . . . . . . . No E - V curve . . . . . . . . . . . . Yes ∆E/ ∆V - V curve . . . . . . . . . . Yes ∆

2E/ ∆V

2 - V curve . . . . . . . . . No


∆V/ ∆t - t curve . . . . . . . . . . No


ET1 0.0000 336.9 0:03 2.8570 2.8570 340.2 3.3 1.2 0:13 4.2850 1.4280 341.4 1.2 0.8 0:19 ET2 5.0000 0.7150 341.8 0.5 0.6 0:24 5.3000 0.3000 342.4 0.5 1.7 0:28 5.6000 0.3000 342.7 0.3 1.1 0:32

15.4400 0.0960 257.6 -7.8 -81.4 3:46EQP1 15.5300 0.0890 249.6 -8.0 -90.0 3:52 15.6110 0.0810 242.5 -7.1 -87.8 3:58 15.7040 0.0930 234.1 -8.3 -89.6 4:05

16.6240 0.0360 106.1 -8.5 -235.1 5:59 16.6550 0.0310 98.8 -7.3 -235.6 6:06EQP2 16.6880 0.0330 90.1 -8.7 -262.4 6:14 16.7180 0.0300 82.7 -7.4 -247.7 6:21 16.7520 0.0340 74.0 -8.7 -256.6 6:29

17.7090 0.0300 -109.1 -13.4 -448.0 9:44 17.7390 0.0300 -123.6 -14.5 -482.5 10:01 17.7690 0.0300 -148.5 -24.9 -831.5 10:25EQP3 17.7990 0.0300 -199.3 -50.8 -1693.0 10:56 17.8290 0.0300 -244.5 -45.2 -1505.6 11:22

20.0000 0.1560 -359.7 -1.7 -11.2 13:14



Anionic components in water soluble metal working fluids

Instruments: METTLER TOLEDO DL70ESMETTLER TOLEDO AT261ST20A Sample changerPrinter

Methods: 081a (calibration factor)081b (content determination)

Accessories: Titration beaker ME-101974Pump SP40/6 ME-65241

Indication: DN100 Infratrode

Sample: Water soluble metalworking fluids5-25 mL(concentration dependent)

Compound: Anionic surfactants


Titrant: Hyamine 1622c(Hyamine) = 0.05 mol/LM = 448.18 g/mol , z = 1

Standard: Water soluble metal workingfluids of known composition

Results: Content determination, method 081b / Titration of used lubricantsMETTLER TOLEDO DL70 Mettler-Toledo, 6300 Giessen Market Support Laboratory

081b Concentr. Determination measured 24-04-1992 12:54 24-04-1992 12:05 Titrator *3* SW Version 2.0 User K.M./Rd.

RESULTS

No Identification Volume Results

1/1 Aliquot 25.0 mL 946.5 mV Starting sign 2.29 mL Consumption 6.88 % Content 1/2 Aliquot 25.0 mL 946.5 mV Starting sign 2.29 mL Consumption 6.88 % Content 1/3 Aliquot 25.0 mL 946.5 mV Starting sign 2.29 mL Consumption 6.88 % Content 1/4 Aliquot 25.0 mL 946.5 mV Starting sign 2.29 mL Consumption 6.88 % Content 1/5 Aliquot 25.0 mL 946.5 mV Starting sign 2.29 mL Consumption 6.88 % Content

STATISTICS Number results R3 n = 5 Mean value x = 6.88 % Content Standard deviation s = 0.003 % Content Rel. standard deviation srel = 0.039 % Outlier test: no outliers!


Comments on method 081b: content determination

• In this application the content of anioniccomponents in water soluble metal working fluidsis determined. These fluids serve as coolers andlubricants of tools and workpieces in metal cuttingprocesses.Through periodical checking of the concentrationthe use of lubricants can be optimized to increasereliability and minimize running expenses andwaste reduction.

• One of the advantages of this method is theelimination of the use of organic solvents (in thecase, carbon tetrachloride).

Principle:

• The determination of the content of anionicsurfactants is based on a comparative titration .First an unused sample of known concentration(in this case 5%) is titrated according to method081a (see next page).From the titrant consumption and the knownconcentration of the water soluble metal workingfluids mixture, a calibration factor is calculatedand stored as auxiliary value H4, which isautomatically taken into account in the maintitration (method 081b, content determination)

• As soon as a new calibration factor is determined,the former auxiliary value is overwritten if theresult meets the defined condition regardingrepeatability.If not, instructions are generated and the set ofmeasurements is interrupted in order to repeat thedetermination of the auxiliary values.

• Then the actual determination of the content inthe sample according to method 081b follows.The starting value of the potential, the mL-consumption and the content are determined, andthe average of the series is calculated.

Method 081b Concentr. Determination Version 24-Apr-1992 12:05

Title Method ID . . . . . . . . . . . . . 081b Title . . . . . . . . . . . . . . . Concentr. Determination Date/time . . . . . . . . . . . . . 24-Apr-1992 12:05 Sample Number samples . . . . . . . . . . . 5 Titration stand . . . . . . . . . . ST20 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 25.0 ID1 . . . . . . . . . . . . . . . . Aliquot Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Pump Auxiliary reagent . . . . . . . . . H 2O Volume [mL] . . . . . . . . . . . . 50.0 Stir Speed [%] . . . . . . . . . . . . . 70 Time [s] . . . . . . . . . . . . . . 120

Measure Sensor . . . . . . . . . . . . . . . DN100 Unit of meas. . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.5

∆t [s] . . . . . . . . . . . . . . 1.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s]. . . . . . . . . . . . 3.0 t(max) [s] . . . . . . . . . . . . 30.0 Calculation Result name . . . . . . . . . . . . Starting sign Formula . . . . . . . . . . . . . . R1=E Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mV Decimal places . . . . . . . . . . . 1 Titration Titrant . . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . . 0.01 Sensor . . . . . . . . . . . . . . . DN100 Unit of meas. . . . . . . . . . . . As installed Titration mode . . . . . . . . . . . EQP Predispensing 1 . . . . . . . . . mL Volume [mL] . . . . . . . . . 0.7 Titrant addition . . . . . . . . INC ∆V [mL] . . . . . . . . . . . 0.05 Measure mode . . . . . . . . . . TFIX ∆t [s] . . . . . . . . . . . . 5.0 Threshold . . . . . . . . . . . . 1200 EQP range . . . . . . . . . . . . Yes Limit A [mV, pH,...] . . . . . 1000.0 Limit B [mV, pH,...] . . . . . 1999.0 Maximum volume [mL] . . . . . . . 6.0 Termination after n EQPs . . . . Yes n = . . . . . . . . . . . . . 1 Evaluation procedure. . . . . . . Maximum Calculation Result name . . . . . . . . . . . . Consumption Formula . . . . . . . . . . . . . . R2=VEQ Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mL Decimal places . . . . . . . . . . . 2 Calculation Result name . . . . . . . . . . . . Content Formula . . . . . . . . . . . . . . R3=VEQ*H4 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . % Decimal places . . . . . . . . . . . 2 Rinse Auxiliary reagent . . . . . . . . . H 2O Volume [mL] . . . . . . . . . . . . 10.0 Conditioning Interval . . . . . . . . . . . . . . 1 Time [s] . . . . . . . . . . . . . . 30 Rinse . . . . . . . . . . . . . . . Yes Auxiliary reagent . . . . . . . . H 2O Volume [mL] . . . . . . . . . . . 10.0 Record Output unit . . . . . . . . . . . . Printer Results last sample . . . . . . . . Yes E - V curve . . . . . . . . . . . . Yes Record Output unit . . . . . . . . . . . . Printer Table of measured values . . . . . . Yes Condition . . . . . . . . . . . . . Yes Condition . . . . . . . . . . . . neq=0 Statistics Ri (i=index) . . . . . . . . . . . . R3 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes

Outlier test . . . . . . . . . . . . Yes Record Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes Conditioning Interval . . . . . . . . . . . . . . 1

Method 081b (content determination)

E – V curve

Authors: K. Mooibroek, D. Rehwald, H.J. Nolte


Method 081a Calculation Constant Version 23-Apr-1992 12:00

Title Method ID . . . . . . . . . . . . . 081a Title . . . . . . . . . . . . . . . Calculation Constant Date/time . . . . . . . . . . . . . 23-Apr-1992 12:00 Rinse Auxiliary reagent . . . . . . . . . H 2O Volume [mL] . . . . . . . . . . . . 25.0 Sample Number samples . . . . . . . . . . . 3 Titration stand . . . . . . . . . . ST20 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 25.0 ID1 . . . . . . . . . . . . . . . . 5% Std. L Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Pump Auxiliary reagent . . . . . . . . . H 2O Volume [mL] . . . . . . . . . . . . 50.0 Stir Speed [%] . . . . . . . . . . . . . 70 Time [s] . . . . . . . . . . . . . . 120

Measure Sensor . . . . . . . . . . . . . . . DN100 Unit of meas. . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.5

∆t [s] . . . . . . . . . . . . . . 1.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s]. . . . . . . . . . . . 3.0 t(max) [s] . . . . . . . . . . . . 30.0 Calculation Result name . . . . . . . . . . . . Starting sign Formula . . . . . . . . . . . . . . R1=E Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mV Decimal places . . . . . . . . . . . 1 Titration Titrant . . . . . . . . . . . . . . Hyamine Concentration [mol/L] . . . . . . . 0.01 Sensor . . . . . . . . . . . . . . . DN100 Unit of meas. . . . . . . . . . . . As installed Titration mode . . . . . . . . . . . EQP Predispensing 1 . . . . . . . . . mL Volume [mL] . . . . . . . . . 1.0 Titrant addition . . . . . . . . INC ∆V [mL] . . . . . . . . . . . 0.05 Measure mode . . . . . . . . . . TFIX ∆t [s] . . . . . . . . . . . . 5.0 Threshold . . . . . . . . . . . . 1200 EQP range . . . . . . . . . . . . Yes Limit A [mV, pH,...] . . . . . 1000.0 Limit B [mV, pH,...] . . . . . 1999.0 Maximum volume [mL] . . . . . . . 6.0 Termination after n EQPs . . . . Yes n = . . . . . . . . . . . . . 1 Evaluation procedure. . . . . . . Maximum Calculation Result name . . . . . . . . . . . . Consumption Formula . . . . . . . . . . . . . . R2=VEQ Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mL Decimal places . . . . . . . . . . . 2 Calculation Result name . . . . . . . . . . . . Factor Formula . . . . . . . . . . . . . . R3=5/VEQ Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . Decimal places . . . . . . . . . . . 3 Rinse Auxiliary reagent . . . . . . . . . H 2O Volume [mL] . . . . . . . . . . . . 10.0 Conditioning Interval . . . . . . . . . . . . . . 1 Time [s] . . . . . . . . . . . . . . 30 Rinse . . . . . . . . . . . . . . . Yes Auxiliary reagent . . . . . . . . H 2O Volume [mL] . . . . . . . . . . . 10.0 Record Output unit . . . . . . . . . . . . Printer Results last sample . . . . . . . . Yes E - V curve . . . . . . . . . . . . Yes Record Output unit . . . . . . . . . . . . Printer Table of measured values . . . . . . Yes Condition . . . . . . . . . . . . . Yes Condition . . . . . . . . . . . . neq=0 Statistics Ri (i=index) . . . . . . . . . . . . R3 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes

Outlier test . . . . . . . . . . . . Yes Auxiliary value ID text . . . . . . . . . . . . . . Factor Formula . . . . . . . . . . . . . . H4= x Condition . . . . . . . . . . . . . Yes Condition . . . . . . . . . . . . srel < 1

Method 081a (calibration factor) Instruction Instruction . . . . . . . . . . . . Attention!srel of > . . . . . . . . . . . . . . . . . Factor determination > . . . . . . . . . . . . . . . . . >1. more titrations? Condition . . . . . . . . . . . . . Yes Condition . . . . . . . . . . . . srel>1 Instruction Instruction . . . . . . . . . . . . Run away test. Repeat > . . . . . . . . . . . . . . . . . with 5 new samples! > . . . . . . . . . . . . . . . . . Condition . . . . . . . . . . . . . Yes Condition . . . . . . . . . . . . srel>1 Record Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes Conditioning Interval . . . . . . . . . . . . . . 1 Time [s] . . . . . . . . . . . . . . 10

General remarks

1) Hyamine is used as a titrant. The equivalence pointis detected through a signal change monitored withthe DN100 Sensor.

2) In both methods 081a and 081b the same samplevolume is titrated (25 mL in this example). Asthese concentration determinations arecomparative methods, no information about Mand z is necessary.

3) If needed, the DN100 sensor is rinsed by immer-sing it in a mixture of solvent, e.g. in ethanol/water(90%/10%) after each titration.

Comments on method 081a: calibration factor

1 Mean stirrer speed, in order to achieve a goodstability of the emulsion.

2,3 Determination of the DN100 Infratrode outputsignal to control the automatic setting. The signalshould be 1000 ± 200 mV.

4 Titration to a maximum signal after passing thethreshold value of 1200 mV.The titration is terminated after the firstequivalence point or after reaching the maximumvolume.

5 Additional information.Output only if no equivalence point has beenfound («condition neq = 0»).

6 Statistics.With outlier test if 5 or more samples have beentitrated.

7 The average of calculation R3 is stored asauxiliary value H4 if the condition srel<1 isfulfilled.The average is stored only if the repeatability issufficiently high. The user is informed when theRSD is above 1%.

8,9 Comments of the DL70 for the user if thecalibration factor could not be stored.

1

2

3

4

5

6

7

8

9


Results: Calibration factor , method 081a / Standard of known concentration (5%)

The DN100 Infratrode

The optoelectronic DN100 sensor is composed of a fibre optics system and evaluation electronics. The emittedlight is reflected and refracted at the boundary layer. The intensity of the received light is dependent on theoptical properties at the interface of the glass tip with the solution. The output signal of the DN100 sensor ishandled like an output signal of an electrode or a phototrode.

General remarks

• The calibration factor, stored as auxiliary H4, is assigned to a certain sample or to a certain type of samples.Immediately before different samples or types of samples are analysed, method 081a has to be run. Thisensures that the correct calculation factor is applied every time.

• Methods 081a and 081b can each be used several times without interruption. The reference samples(calibration factor) and those to be analysed are put on the sample changer ST20A in the same order. Witheach new series of reference samples the value H4 is overwritten .

• Always take the same sample volume for both methods. Adjust the sample volume to a titrant consumptionof about 5 mL.

• The initial signal of the DN100 sensor is automatically set to about 1000 mV at the beginning of a titration.During the adjustment period, the green and red LED is blinking. The adjustment time is about 20 seconds(red light becomes green). With milky samples, the adjustment time may be longer. As soon as the DN100sensor is ready to be used, the green display will be blinking. If the insertion depth is insufficient, the redlight is blinking.

• The Infratrode has to be carefully cleaned after each titration, so that leftovers, e.g. an oil film, do not affectthe following titration. This is automatically performed by the function «Conditioning».

• Defoamers can affect the titration.• Formation of air bubbles has to be avoided, e.g. by controlling the stirrer speed, sample addition, and

keeping a constant temperature.

METTLER TOLEDO DL70 Mettler-Toledo, 6300 Giessen Market Support Laboratory

081a Calculation Constant measured 23-04-1992 12:35 23-04-1992 12:00 Titrator *3* SW Version 2.0 User K.M./Rd.

RESULTS

No Identification Volume Results

1/1 5% Std. L 25.0 mL 985.9 mV Starting sign 2.13 mL Consumption 2.347 Factor 1/2 5% Std. L 25.0 mL 1005.4 mV Starting sign 2.14 mL Consumption 2.339 Factor 1/3 5% Std. L 25.0 mL 965.5 mV Starting sign 2.14 mL Consumption 2.338 Factor

STATISTICS Number results R3 n = 3 Mean value x = 2.341 Factor Standard deviation s = 0.0048 Factor Rel. standard deviation srel = 0.203 %

AUXILIARY VALUE New Value H4 n = 2.341421 Factor


Surfactant titration: Comparison of different techniques

Titer determinations with standard solutions

A useful test of the different methods is the titer determination using the same standard solution (SDSand CPC, respectively). A comparison of the results is shown in table 1. The precision (repeatability),indicated by the relative standard deviation RSD, is very good for all methods, with values reachingdown to 0.183 %.The titer values vary from 0.9967 to 1.0461 for Hyamine, and from 0.9560 to 1.0319 for SDS. The2P-titration methods (2P DL58 and Mixed 2P) give slightly different values (1.0461 and 1.0441 forHyamine, 0.9560 and 1.0319 for SDS) than with the turbidimetric (DP550) and potentiometrictechniques (SSE) due to the formation of bubbles and emulsions which increase the turbidity. Thisaffects the photometric detection with the phototrode.

Recovery tests with SDS and CPC solutions

5 mL 0.004 M SDS and 0.004 M CPC have been used as standard solutions to test the recovery. Thesamples were titrated with 0.004 M Hyamine and SDS, respectively. Very good agreement with thetheoretical value of 100% was achieved with all four methods and both standard solutions, althoughthe precision of the 2P DL58 method was only ca. 1.8 %. This is due to the formation of small waterbubbles on the mirror and window of the phototrode screw-on assembly during signal acquisition(slow stirring speed) leading to a noisy signal, and is also responsible for the higher RSD values.

Tab.2: Recovery

Tab.1: Comparison of titer determinations

2P DL58 Mixed 2P DP550 SSE

n Recovery RSD n Recovery RSD n Recovery RSD n Recovery RSD(%) (%) (%) (%) (%) (%) (%) (%)

SDS 4 98.28 1.78 5 99.49 0.62 6 100.15 0.13 5 99.95 0.75

CPC 4 100.86 1.79 6 100.15 0.61 7 100.83 0.18 6 100.62 0.73

Titrant 2P DL58 Mixed 2P DP550 SSE

n Titer RSD n Titer RSD n Titer RSD n Titer RSD(%) (%) (%) (%)

Hyamine 5 1.0461 0.562 5 1.0441 0.229 5 1.0104 0.183 5 0.9967 0.761

SDS 3 0.9560 0.821 6 1.0319 0.763 6 1.0083 0.325 6 1.0128 0.450


Anionic content determination in formulated products

Two formulations (Liquid det. 1 and 2) and 2 commercially available products (Liquid det. 3 and 4)have been analysed by four different methods. Where possible, composition, type and content valuesof the surfactants were indicated (information from the producer).To allow a significant comparison, the pH value was adjusted to pH 1-2 by adding 10 mL 0.1 Msulfuric acid to reproduce the same pH value conditions as for the classical 2P titration, if not indicatedotherwise by the analysis procedure of the producer (Liq. Det. 1 and 2 have been analysed at pH 3 inorder to take into account the betaine content).Note that the determinations with a surfactant sensitive electrode (SSE) were all performed at pH 3since a pH lower than 2 can damage the membrane.

Nominal value: Theoretical composition of the sample as total washing active matter. It is obtainedby summing the percentages of all surfactant components in the sample.

Reference: Value given by the producer and mostly based on classical two-phase titration. Itindicates the total washing active matter.


Tab.3: Anionic content determination in various products

2P DL58 Mixed 2P DP550 SSE COMMENTS

Content (%) Content (%) Content (%) Content (%) Reference Nominal value

RSD (%), (n) RSD (%), (n) RSD (%), (n) RSD (%), (n) (%) (%)

Liq. det. 1 17.84 17.05 17.24 (n) 17.27 17.1 18.0 Average 3.43 (6) 1.19 (6) 0.09 (5) 0.64 (6) pH 3 Fat Alc. Ethersulphate 10%

M=387 Sec. Alk. sulphonate 6%

14.21 14.85 14.12 17.45 (n) - Betaine 2 %

0.51 (5) 0.81 (5) 0.25 (3) 1.10 (4) pH 1-2

Liq. det. 2 31.13 35.30 34.49 (n) 34.13 32.8 38.5 Average 3.17 (5) 0.54 (6) 0.02 (5) 0.40 (6) pH 3 Fat Alc. Ethersulphate 11%

M=362 Sec. Alk. sulphonate 20%

30.84 30.67 30.42 35.59 (n) - Betaine 3.5%

1.48 (5) 0.42 (5) 0.10 (5) 0.70 (5) pH 1-2 7 EO Nonionic 4 %

Liq. det. 3 33.10 32.12 30.94 34.58 (pH 3) - 33.0 Average 0.50 (5) 0.02 (5) 1.97 (7) 0.28 (6) pH 1-2 Anionics A (346) 27%

M = 353.09 Anionics B (385) 6%

34.44 33.85 - additional comp. unknown

0.07 (5) 1.23 (6) (n)

Liq. det. 4 13.48 14.15 13.24 16.35 (pH 3) 14.18 15-30 anionic surf. as SDS, 0.78 (5) 0.78 (5) 0.94 (4) 0.28 (6) pH 1-2 unknown composition

M = 288.3814.32 15.25 -1.56 (5) 0.95 (10) (n)


Liquid detergent 1:

This product contains 10% fatty alcohol ether sulphate, 6% secondary alkanesulphonate, and 2% betaine (no-minal value: 18% washing active matter, average M = 387 g/mol). According to the producer, 2P-titration isperformed at pH 3 (average content result: 17.1%) to avoid interferences due to betaines [see ref. 4]. This isshown by the results obtained with the standard acid mixed indicator (pH 1-2). At this pH value, betaines areprotonated and they neutralize other anionic surfactants present in the sample. The neutralized anionic surfactantscannot form a precipitate with the titrant, and the results indicate a lower content by approx. 3.3%.All results at pH 3 agree very well with the reference value, and their values vary from 17.05% to 17.84%.

Liquid detergent 2

Liquid detergent 2 has a similar composition to the previous sample. In addition, nonionic surfactants arecontained in the formulated product (average M = 362). 2P-titration performed at pH 3 gives a reference valueof 32.8% (average M = 362). Measurements at pH 3 vary between 31.13% and 35.30%. Note the low precisionachieved with the automatic 2P-titration (RSD: 3.17%) relative to the other techniques, i.e. mixed 2P, DP550and SSE.

Particularly low are the content values obtained at pH 1-2 , ca. 30.5 %, although the repeatability is very good(down to RSD: 0.01%). This is to be expected since at this pH value betaines are protonated and neutralize otheranionic surfactants, and therefore the latter can not be precipitated by titration.

The comparison of content values obtained at pH 3 and without pH adjustment, for all techniques, confirm thisexplanation. In addition, the large content of secondary alkanesulphonate (20%) can be a possible reason for thehigher values found by potentiometric titration with a SSE both at pH 3 and without pH adjustment.

Liquid detergent 3

The anionic content has a nominal value of 33%, which consists of 27% of surfactant A (M=346) and 6% ofcomponent B (M=385). Nature and chemical structure of these surfactants are unknown. Based on thisinformation, an average molecular weight of M=353.09 was calculated.

The results obtained at pH 1-2 with 2P DL58, mixed 2P and SSE (pH 3) techniques are in good agreementwith the nominal value of 33% (absolute deviations: 1-2%). The DP550 method shows a consistently lowercontent, although the precision is excellent (RSD down to 0.019% !). Since the composition is not completelyknown, it is only possible to speculate on the origin of such low content value. For instance, at pH 1-2 theprotonation of surfactant components such as betaines is a conceivable reason for an uncomplete precipitation.This is also suggested by the results obtained without pH adjustment, i.e. when the sample is simply dissolvedin water. In this case, a higher content of 34.44% is found which indicates the presence of surfactant speciesstrongly dependent on pH value, e.g. betaines.

This hypothesis is confirmed by potentiometric determinations with SSE at both pH 3 and without pH adjustment.The results are slightly higher (34.58% and 33.85%, respectively) than the nominal value of 33%, and theprecision varies between 0.276% (pH 3) and 1.23% (without pH adjustment).

Liquid detergent 4

The only information available was the indication of an anionic surfactant content of 15-30%. Thus, to comparethe results obtained the content was expressed as % SDS (M=288.38). An independent laboratory performedthe determination by mixed 2P-titration, achieving a value of 14.18% (SDS). The results show a very goodagreement with the reference value of 14.18%, with an absolute content deviation ranging from 0.03% to1.07%.

Again, potentiometric titration shows a slightly higher content with respect to the other techniques. Since thecomposition is unknown, it is not possible to identify the exact reason for this slightly higher content, whichreaches 16.35% at pH 3. Conceivable explainations can be:1) the higher sensitivity of the SSE with respect to photometric techniques [see ref. 4],2) if present, betaines affecting the anionic content determination at pH 1-2,3) 2P-titration: incomplete precipitation and extraction into the chloroform phase.Since the composition is unknown, the effect due to additional components can not be quantified exactly.


Conclusions

There is no general titration method which can be used for all possible formulations and products.When the sample consists of one pure surfactant component, e.g. in raw materials, the determinationis straightforward. In the case of formulated products, i.e. products containing various surfactants andadditional components, a specific method with appropriate detection technique must be chosen,developed and optimized taking into account:

• Additional surfactant components present in the sample;

• Appropriate pH values;

• Additional components such as salts, abrasive particles, fragrances.

Two-phase titration (2P):

This volumetric technique is still the reference method in surfactant titration. Its main advantage is theextraction of the non polar titrant-analyte complex into the organic phase: matrix effects, i.e.interferences due to additional components present in the sample, can be avoided. The 2P-titration canbe automated by a special function in the DL58 and a phototrode. This method is particularly suitedfor the analysis of anionic and cationic surfactants. Methods based on 2P-titration of nonionic surfactantscontaining EO-units and of amphoteric surfactants are also described in the literature [in particular,see ref. 1 and 3].

Mixed two-phase titration:

In classical two-phase titration the phase separation is always the time-consuming step. For someionic surfactants, the mixed two-phase titration can be used, since the phase separation can be completelyavoided and therefore the analysis time can be reduced consistently.

Turbidimetric titration:

A fast method is the turbidimetric titration of ionic surfactants with photometric indication. Thephototrode employed does not need conditioning and the maintenance is reduced to the minimum.Also the use of organic solvents is avoided. On the other hand, there is no extraction of the complexinto the organic phase, therefore interferences can become a serious problem. This method is mostsuited for ionic surfactants. In addition, nonionic surfactants (raw materials) and a pure solution ofbetaines (amphoteric surfactants) were titrated using sodium tetraphenylborate as a titrant.

Potentiometric techniques: SSE and non aqueous titration

The titration of ionic surfactants by a SSE is rather straightforward. This sensor is suitable for theanalysis of all types of surfactants, but appropriate conditioning and accurate maintenance of the SSEbecome very relevant. Thorough cleaning of the SSE membrane is crucial, since it can be coated bythe precipitate, in particular when titrating nonionic surfactants. An alternative technique is thepotentiometric titration in nonaqueous solution by a pH-combination electrode. With this method thecontent of betaines, the most used amphoteric surfactants in cosmetics, was determined in a shampoo.

Titration with the DN100 Infratrode

This sensor was developed for the determination of ionic surfactants in water-soluble cooling lubricants,and it is limited to this application. Due to its robustness and reduced maintenance, it is particularlysuited for routine analysis with a high sample throughput.


Checklist for surfactant titration

Nature of the sample:

• Raw material or finished product / formulation• Qualitative composition: which surfactants are present in the sample ?• Quantitative composition: what is the surfactant content ?• Additional components: salts, fragrances, alcohol, water.

Analysis:

• What is the momentary analytical procedure used ?⇒ detailed information is necessary.

• If different surfactants are present: possible interferences ?• pH value: possible interferences ?

Sample preparation:

• Finished products / formulations :Ιs a separation step of the components necessary before titration?

• pH value: Is a pH-adjustment necessary ?• Known composition of a sample

⇒ choice of the correct pH value to avoid interferences.

CommentDetailed information is crucial to achieve correct results.

Tips and tricksR. Schulz has extensively described many practical aspects concerning surfactant titration. For furtherinformation, consult reference [4].

I. Properties of surfactants

Surface active behaviour• Migration and enrichment at solution surfaces and interfaces (e.g., glass-water, water-air)

⇒ Avoid too many dilution steps.• Heterogeneous concentration in glass flask, especially when content <1 mg/L• Enrichment of cationic surfactants on glass surfaces: the positive charge of the cationic surfactants is

attracted by the negatively polarised glass surface of a bottle. This leads to a lower concentration ofcationic titrants such has Hyamine, CPC and DDMICl.

Foam formation• Higher surfactant concentration in foam than in solution.

⇒ Avoid shaking and strong stirring during sample preparation.⇒ Add few mL methanol or other alcohols to reduce foam (max. content: 5-10% v/v).

Micelle formation (self-aggregation)• Strongly dependent on concentration• Surfactant molecules in micelles are not available for titration. They become available only after

titration of molecules in solution.⇒ Too fast a titration leads to lower results.

• Direct measurements as for metal ions are generally not possible.


II. Surfactant titration: requirements

• Precipitation reactionThe analyte has to be titrated with a counter ionic surfactant leading to the precipitation of a titrant-analyte complex.

• Complete precipitation of the titrant-analyte complexSurfactants molecules have alkyl chains of various lengths. In general, a chain with more than 12 carbonatoms is completely precipitated, a partial precipitation can occur for chains varying between C

8-C

12 ,

and chains with less than 8 carbon atoms are difficult to titrate.⇒ In general, DDMICl as titrant leads to better results compared to CPC and Hyamine.

• Solubility product of the analyte-titrant complex formedIt depends on the alkyl chain length of the analyte: shorter chain ⇒ higher solubility.

• Endpoint indicationThe precipitation reaction leads to a potential change (potentiometric indication), an increase inturbidity or to a colour change (photometric indication) when indicators are used.

III. Practical hints

• Titrant• Choice of the appropriate titrant for a complete precipitation

⇒ Best results are obtained with DDMICl (compared to CPC and Hyamine)DDMICl: for instance, Fluka no. 36757, or Aldrich no. 43378-0Hyamine: for instance, Fluka no. 53571 (53572), or Merck 112058 (115480)CPC: for instance, Fluka no. 52349 (52350), or Merck 102340

• Cationic surfactant molecules cover a glass surface forming a layer. Some time is needed toreach saturation of the glass surface. When preparing a fresh titrant solution, it is thereforerecommended to allow saturation of the glass surface of the flask, e.g. over night [4].

• Sample size• General rule: avoid too small a sample size (lower content).• Surfactants with many hydrophilic groups such as EO-units ( -(CH

2-CH

2-O-)

n ):

⇒ increase sample size• Analyte with short alkyl chains and broad chain length distribution:

⇒ increase sample size

• Titration speed• A precipitation reaction requires the appropriate titration time

⇒ Do not titrate too fast

• Chemical structure• Alkyl ether sulphates (anionics) with more than 10 EO-units must be titrated as

nonionic surfactants• The number of polar groups (e.g., ethers) affects the titration results.• The alkyl chain length affects the titration curve.• The presence of nonionic surfactants can affect the analysis of ionic surfactants.

• Additional interferences

• Salts affect the titration curve (potentiometric detection): high salt concentration ⇒ flat curve• The influence of insoluble substances, e.g., abrasive particles in tooth paste, can be decreased

by adding methanol to the sample (5-10% v/v).• Deionized water can contain molecules arising from the ion exchange cartridge material (e.g.,

sulphonates) and can lead to wrong content results.⇒ blank value determination.


Literature

[1] Thomas M. Schmitt,«Analysis of Surfactants», in Surfactant Science Series, Vol. 40,Marcel Dekker, Inc., New York , Basel, Hong Kong, 1990, 1992

[2] D. C. Cullum, «Introduction to Surfactant Analysis»,Blackie Academic & Professional, 1994.

[3] Dietrich O. Hummel«Analyse der Tenside», 2nd Edition, Carl Hanser Verlag, München Wien, 1995.

[4] Reiner Schulz, «Titration von Tensiden und Pharmaka»,Verlag für Chemische Industrie, H. Ziolkowsky GmbH, Augsburg (D), 1996 (German).

[5] G. Krusche,«Zur Analytik der Tenside», in «Die Tenside», Kap. 5,Eds. Dr. K. Kosswig / Dr. H. Sache, Carl Hanser Verlag, München Wien 1993, pp. 251-279

[6] Ch. M. Walter, C. A. De Caro,«Tenside titration: a practical discussion»,in «Proceedings of the 4th World Surfactant Congress», Barcelona, Spain, 3-7.6.1996,Vol. 1, pp. 432-445.

[7] a) ASTM D 3049-89: «Synthetic Anionic Ingredients by Cationic Titration», 1989.b) ISO 2271: «Determination of Anionic-Active Matter. Direct Two-Phase Titration Proc.»,1989.c) BSI 3672: «Analysis of formulated detergents», Section 3.1, «Method for determination

of cationic-active matter content», 1990.d) DIN 38409-H23-1: «Summarische Wirkungs- und Stoffkenngrössen: Bestimmung der

methylenblauaktiven und der bismutaktiven Substanzen», 1980, pp.1-13.

[8] Lebensmittel und Veterinäruntersuchungsamt des Landes Schleswig-Holstein,«Bestimmung anionischer Tenside mit der 2-Phasen-Titration nach Epton mittels Titrations-prozessorsystems DL67», Prüfmethode M-3004-01.500, Februar 1997.

[9] H. Block,«Mikroprozessorgesteuerte Phototitration anionischer und kationischer Tenside in Wasch-und Reinigungsmitteln»,Lebensmittechem. Gerichtl. Chem. 39, 6-21 (1985)

[10] N. Buschmann, H. Wille«Titration of amphoteric surfactants - a comparison of methods»,Atti delle 7e Giornate CID (Conference Proceedings), Comitato Italiano dei DerivatiTensioattivi, Genova, Italy, 22-24.10.97, and references therein.


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