direct measurement with ion selective electrodesbikeitech.com/datas/es_free3/f_4979110fc3bc9.pdf ·...

METTLER TOLEDO Titrators

Direct Measurementwith Ion Selective Electrodes

Application brochure 6

Na+

F - Cl-

K+

NO -3

/ 68 METTLER TOLEDO DL5x and DL7x Titrators Direct Measurement with Ion Selective Electrodes

Editorial

Dear ReaderUsing ion selective electrodes (ISE) to determine ion contents, today’s analyst has a simple, reliableand versatile method at hand.

It pleases us to present these applications to you. Using lots of examples, they will show you how youcan use the METTLER TOLEDO DX ion selective electrode series, together with titrators DL67 /DL70ES / DL77, to solve many of your analysis tasks. This builds up on the many possibilities foradapting methods offered by titrators DL67 / DL70ES / DL77. This, of course, together with the clearuser guidance offered by alphanumeric and grafic displays in plain language.

The applications examples are mostly taken from the area of foods and beverages. However, they alsorepresent samples from other areas such as chemicals, cosmetics and environmental protection.

Matrix effects and the influence of interfering ions (cross sensitivity) are explained. Hints for pre-venting or reducing these are given wherever possible. Also included is a list of references which wemention explicitly in this context.

A load of practical tips and hints are included with the individual measurements. These are summa-rized in the chapter on trouble-shooting.

A further benefit of the use of ion selective electrodes is the minimal use of chemicals and the avoid-ance of environmentally damaging wastes, ecologically as well as economically an important consid-eration.

Unless the sample must be buffered, the method is also non-destructive.

The analyses were mostly performed with perserverance and success in our lab by Anke Stock, as apart of the work required for her to attain her chemical engineering Masters degree.

Albert Aichert, Market Support AnaChem, included numerous additions and edited this brochure.Many thanks to both authors.

A further brochure will describe the addition procedures also used in measurements with ion selectiveelectrodes.

We are convinced that the inclined reader, thanks to the broad scope of information, will soon feel atease using ion selective electrodes. The new tools should help him/her readily solve new problems.

We wish you lots of luck using ion selective electrodes together with our titrators .

Georg Reutemann Rolf M. Rohner

Manager Market Support Marketing Manager

Direct Measurement with Ion Selective Electrodes METTLER TOLEDO DL5x and DL7x Titrators / 68

Contents

1. Fluoride Selective Electrode ........................................................................................ 4

M101 Calibrating the Fluoride Electrode ............................................................................... 6

M102 Fluoride Determination with Fluoride Ion Selective Electrode ................................... 8

M071 Fluoride Determination in Water ............................................................................... 12

2. Chloride Selective Electrode...................................................................................... 14

M103 Calibrating the Chloride Electrode ............................................................................ 16

M104 Chloride Determination with Ion Selective Chloride Electrode ................................ 18

M105 Chloride Determination in Canned Vegetables .......................................................... 22

3. Nitrate Selective Electrode ........................................................................................ 24

M106 Calibrating the Nitrate Electrode ............................................................................... 26

M107 Automatic Three-point Calibration of the Nitrate Electrode ..................................... 28

M108 Nitrate Determination with Ion Selective Electrode .................................................. 30

M109 Nitrate Determination in Reference Samples ............................................................ 34

4. Potassium Selective Electrode ................................................................................... 36

M110 Calibration of the Potassium Electrode...................................................................... 38

M111 Potassium Determination with Ion Selective Electrode............................................. 40

5. Sodium Selective Electrode ....................................................................................... 44

M112 Calibration of the Sodium Electrode.......................................................................... 46

M113 Sodium Determination with Ion Selective Electrode................................................. 48

6. Trouble-shooting ........................................................................................................ 52

7. Summary of the Ion Selective Electrodes and Reagents Used .................................. 54

8. Literature .................................................................................................................... 56

9. Sample index ...............................................................................................................63


1. Fluoride Selective Electrode

Theory The fluoride electrode is a solid state membrane electrode. The active electrodephase is a nearly water insoluble lanthanide fluoride monocrystal which is indirect contact with the measurement solution. The potential difference derivedfrom the equation

LaF3 ⇔ La+3 + 3 F- is conducted by the electrolyte and a noble metal wire.

The theoretical detection limit of the fluoride electrode is determined by the lowsolubility of the LaF3 crystal (10-26). Using TISAB to adjust the pH value and theionic strength, linear calibration curves of 0.1 – 10-6 mol/L are attained; thedetection limit lies slightly higher than 10-7 mol/L. The slope, theoreticallycalculated from the Nernst equation to be 59.16 mV/pF at 25°C, usually lies at58-59 mV/pF in practice.

Electrodes

Bridging electrolyte As bridging electrolyte for the reference electrode, a 1 mol/L KNO3 solution is

used.

Conditioning For the determination of concentrations under 1 mg/L, the electrode should beconditioned in deionized water for approx. 30 minutes.

Storage Store electrodes dry or in a dilute fluoride solution. The electrolyte should not besubmerged for long in solutions containing TISAB, as the crystal surface isdamaged by complexing agents.

Handling The lanthanide fluoride crystal is sensitive to mechanical impact. Cracks andscratches render the electrode useless. Avoid fat deposits on the crystal; do nottouch with bare fingers.

Contamination A sluggish or no response indicates that the sensor is contaminated. Deposits onthe crystal can be removed carefully by wiping with a soft tissue. Afterwards itis advantageous to condition for several minuts in a dilute fluoride solution.

Repolish non-regenerable modules with an aqeous slurry of aluminum oxide orwith toothpaste.

Reagents

TISAB solutions: (Total Ionic Strength Adjustment Buffer)

METTLER TOLEDO TISAB 3 Art. No. 51 340 064 (mix 1:10 with sample)

MERCK TISAB I Art. No. 153668 (1:1 mix with sample), contains NaClTISAB III Art. No. 116770 (1:10 mix with sample), contains NH

4Cl

Self made In 700 mL deion. water are dissolved 58 g NaCl p.a. and 5 g CDTA (1,2-diaminocyclohexane-N,N,N’,N’-tetraacetate, Titriplex IV from MERCK, No.108424, or Complexon IV p.a.) by adding 5 mol/L NaOH solution.Add 57 mL glacial acetic acid p.a and adjust to pH 5.5 using sodium hydrox-ide c(NaOH) = 5 mol/L at 20°C. Adjust volume to 1000 mL using deion wa-ter. The pH value of this solution should be 5.3 (20°C).


F- stock solution: Fluoride standard solution (potassium fluoride in water) 1.000 g ± 0.002 g F-

MERCK Art. No. 109869Fill to 1000 mL with deion. water and decant to plastic bottle.1 mL = 1 mg fluoride.Appropriate standard solutions are made from this stock.

RemarkspH Value At pH values under pH=5, HF and HF2

- are formed. Both are not detected by thefluoride electrode. At pH values over pH=8, La(OH)3 is formed and the electroderesponds increasingly to OH- ions.

Interfering ions Metal ions such as Al3+, Fe3+, Si4+, Ca2+, Fe2+, and other polyvalent ions formcomplexes with fluoride, some of which are stable. The fluoride bound in thismanner can be released for determination by adding Complexon IV (found inTISAB solution) for preferential complexing.

Ionic strength The total activity of calibration and measurement solutions must be constant. Byadding a constant amount of TISAB solution, the pH is buffered sufficiently andthe solution is adjusted to a constant ionic strength.

Samples Samples and standard solutions should be stored only in PE or PP bottles withfluoride-saturated walls.

Glass utensils Any glass utensils used should first be rinsed with sodium hydroxide (0.01 mol/L) to block glass against fluoride ions.

Deion. water The deion. water used to make solutions should be made basic using sodiumhydroxide. This prevents fluoride loss.

Application and Use

Application The fluoride electrode is used for fluoride determination in air, water, beverages,foods, dental hygiene articles, organic compounds, vegetation, soil and rocksamples.

Use Direct measurement with an ion selective electrode is the method of choice forfluoride determination. The high selectivity and large concentration range makethis method universally applicable .

Alternatives Ion chromatography.Potentiometric titration using a fluoride electrode and lanthanide nitrate astitrant at pH=6.3 F- + La(NO3)3 = LaF3 + 3 NO3

-

This method is applicable only for higher fluoride concentrations (more than20 mg/L). It is rarely used in practice.

Advantages - wide application range (1000 - 0.01 mg/L)- the determination is fast and simple- no heavy metal wastes- small investment (compared to ion chromatography)

Disadvantages none

METTLER TOLEDO


M101 Calibrating the Fluoride Electrode

Sample: 50 mL fluoride solution10-1 g/L, 10-2 g/L, 10-4 g/L

Substance: FluorideM = 18.998 g/mol , z = 1

Preparation: 5 mL TISAB III MERCK

Titrant: --

Standard: --

Instruments: METTLER TOLEDO DL70ESHP Deskjet 500 PrinterMT AT261 Balance

Method: F007

Accessories: Titration beaker ME-101974DT120 (temp. sensor Pt100)

Indication: DX219 Fluoride ISEDX200 Reference electrode(bridge electrolyte: 1 M KNO3)

Results: METTLER DL70ES Titrator V3.0 Mettler-Toledo AG AA01 Market Support Laboratory

Method F007 Calibration F--sensor 09-Nov-1993 17:46 User aa Measured 10-Nov-1993 10:27

RESULTS

No ID1 ID2 Sample amount and results

1/1 10-4 g/L 50.0 mL pH,pM,pX 4.000 R1 = 158.267 mV Potential 1/2 10-2 g/L 50.0 mL pH,pM,pX 2.000 R1 = 42.349 mV Potential 1/3 10-1 g/L 50.0 mL pH,pM,pX 1.000 R1 = -15.540 mV Potential

CALIBRATIONSensor F--sensor

Buffer type pH,pM,pX Zero point 1.269 pX0 Slope 57.94 mV/pX Calibration temperature 21.7 °C


Method Remarks1) Calibration and measurement solutions should

always be at the same temperature.

2) All measurements should be performed usingthe same stirring conditions. This means thesame speed, stirrer type, distance to electrodeetc.

3) The calibration parameters are automaticallystored in the installation data by the titrator.They are then referred to the sensor indicatedin the method and are applicable only for thissensor.

4) Up to 8 standard solutions can be used for thecalibration. If only one standard is used, thetitrator will correct only the zero point.

5) Rinse electrode with deion. water after eachmeasurement and remove adhering waterdrops with a soft paper tissue.

6) It is necessary to stir for approx. 5 minutes eachmeasurement to attain a stable measured value.

7) For a three-point calibration with automaticproduction of the standard solutions, see thenitrate electrode.

Disposal--

Other titratorsDL50 Graphix, DL53/55/58, DL77 titrators.

Method F007 Calibration F--sensor Version 09-Nov-1993 17:46

Title Method ID . . . . . . . . . . . . . F007 Title . . . . . . . . . . . . . Calibration F--sensor Date/time . . . . . . . . . . . . . 09-Nov-1993 17:46Sample Number samples . . . . . . . . . . 3 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 300Measure Sensor . . . . . . . . . . . . . . F--sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 30.0Calculation Result name . . . . . . . . . . . . Potential Formula . . . . . . . . . . . . . . R=E Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mV Decimal places . . . . . . . . . . . 3Calibration Sensor . . . . . . . . . . . . . . . F--sensor Buffer type . . . . . . . . . . . . pH,pM,pX First buffer . . . . . . . . . . 4.0 Second buffer . . . . . . . . . . 2.0 Third buffer . . . . . . . . . . 1.0 Fourth buffer . . . . . . . . . . 0.0 Fifth buffer . . . . . . . . . . 0.0 Sixth buffer . . . . . . . . . . 0.0 Seventh buffer . . . . . . . . . 0.0 Eighth buffer . . . . . . . . . . 0.0 Ri (i=index) . . . . . . . . . . . . R1 Minimal slope . . . . . . . . . . . 50.0 Maximal slope . . . . . . . . . . . 60.0Record Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes

Author: Albert Aichert

Typical calibration curve of a fluoride selective electrode with TISAB solution

METTLER TOLEDO


M102 Fluoride Determination with Fluoride Ion Selective Electrode

Sample: 50 mL sample solution with1000 to 0.01 mg/L fluoride



Titrant: -

Standard: -

Instruments: METTLER TOLEDO DL70ESPrinter (HP Desk Jet 500)

Method: F00A, F00B



Repeatability and Recovery Rate

1. For these measurements, aqueous fluoride solutions from the fluoride standard solution (potas-sium fluoride in water) 1.000 g ± 0.002 g fluoride, MERCK Art. No. 109869, were used.

2. The fluoride electrode was recalibrated at least once a day using 10 mg/L and 0.1 mg/L standardsolutions (sometimes necessary after 3-4 series).

3. Preparation: Add 5 mL TISAB III to 50 mL sample solution and measure.

Concentration Recovery srel from several series (n=6)mg / L % Method A Method B

1000 100 - 105 % 0.09 - 0.20 % 0.15 - 0.26 %

100 100 - 103 % 0.06 - 0.20 % 0.11 - 0.20 %

10 99 - 101 % 0.13 - 0.26 % 0.18 - 0.24 %

1 98 - 100 % 0.15 - 0.31 % 0.19 - 0.36 %

0.1 99 - 102 % 0.15 - 0.45 % 0.27 - 0.51 %

0.05 97 - 101 % 0.10 - 0.84 % 0.12 - 0.91 %

0.01 155 - 181 % 0.38 - 4.6 % 0.42 - 2.47 %

Result:Method (A) allows to obtain a a better repeatability, expressed as relative standard deviation srel.However, the adjstment time prior to the measurement is crucial for good repeatability. At highconcentrations (1000 - 0.1 mg/L) the stirring time is 5 minutes. At low concentrations, longer times arenecessary: for 0.05 g/L approx. 10 minutes, and for 0.01 g/L approx. 20 minutes.

The concentration 0.01 mg/L is not in the linear range (see calibration curve page 7). The range ofconcentrations for fluoride sensitive electrodes was therefore limited from 100 to 0.05 mg/L.


Method A

Other titratorsDL53+, DL55+, DL58, DL77 titrators. Author: Albert Aichert

Method F00A F--content Version 10-Sep-1993 16:05

Title Method ID . . . . . . . . . . . . . F00A Title . . . . . . . . . . . . . F--content Date/time . . . . . . . . . . . . . 10-Sep-1993 16:05Sample Number samples . . . . . . . . . . 6 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 300Measure Sensor . . . . . . . . . . . . . . F--sensor Unit of meas . . . . . . . . . . . . As installed ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Measure Sensor . . . . . . . . . . . . . . F--sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 1.0 t(max) [s] . . . . . . . . . . . . . 2.0Measure Sensor . . . . . . . . . . . . . . F--sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 1.0 t(max) [s] . . . . . . . . . . . . . 2.0Measure Sensor . . . . . . . . . . . . . . F--sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 1.0 t(max) [s] . . . . . . . . . . . . . 2.0Measure Sensor . . . . . . . . . . . . . . F--sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 1.0 t(max) [s] . . . . . . . . . . . . . 2.0Measure Sensor . . . . . . . . . . . . . . F--sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 1.0 t(max) [s] . . . . . . . . . . . . . 2.0Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R1=E[1] Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . p(F-) Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . F--single Formula . . . . . . . . . . . . . . R2=pw(-E[1])*1000 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mg/L Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R3=(C3+E[5]+E[6])/6 Constant . . . . . . . . . . . . . . C3=E[1]+E[2]+E[3]+E[4] Result unit . . . . . . . . . . . . Decimal places . . . . . . . . . . . 3Calculation Result name . . . . . . . . . . . . F--x of 6 Formula . . . . . . . . . . . . . . R4=pw(-R3)*1000 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mg/L Decimal places . . . . . . . . . . . 4Statistics Ri (i=index) . . . . . . . . . . . . R2 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesStatistics Ri (i=index) . . . . . . . . . . . . R4 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesRecord Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes

Method B

Remarks

Method A1) Stirring during 5 minutes.

2) Acquisition of six values (six Measure-func-tions) at an interval of 1-2 s.

3) The fluoride concentration is calculated fromthe mean of these six values.

Method B1) Stirring during 5 minutes.

2) Acquisition of one value.

3) If the sample is diluted for the measurement,the dilution factor can be entered as a correc-tion factor (f) for each sample. This will beused in the calculation.

Method F00B F--content Version 16-Sep-1993 10:21

Title Method ID . . . . . . . . . . . . . F00B Title . . . . . . . . . . . . . F--content Date/time . . . . . . . . . . . . . 16-Sep-1993 10:21Sample Number samples . . . . . . . . . . 6 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . F-

Molar mass M . . . . . . . . . . . . 18.99840 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 300Measure Sensor . . . . . . . . . . . . . . F--sensor Unit of meas . . . . . . . . . . . . As installed ∆E [mV] . . . . . . . . . . . . . . 0.3 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 3.0 t(max) [s] . . . . . . . . . . . . . 30.0Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R=E Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . p(F-) Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . F--content Formula . . . . . . . . . . . . . . R2=pw(-E)*1000*f Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mg/L

Decimal places . . . . . . . . . . . 3Statistics Ri (i=index) . . . . . . . . . . . . R2 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesRecord Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes

Disposal--


Results

Sample Direct measurement with ISE Nominal content(number) F- content srel (Producer specification)

Drinking water 0.056 mg/L 0.79 % not over 1.5 mg/L *(n = 5)

Snow 0.0066 mg/L 14.9 % none given(n = 5)

Mineral water 0.109 mg/L 0.5 % 0.13 mg/L(n = 5) (analysis 1983)

Wine 0.176 mg/L 2.0 % none given(n = 5)

Milk 0.023 mg/L 2.1 % none given(n = 3)

Table salt 233 mg/kg 1.2 % 250 mg/kg(n = 10) ± 20 %

Toothpaste 0.117 % 0.9 % 0.113 %(n = 2)

Fluoride tablet 1.064 mg/tab. 2.4 % 1 mg / tablet(n = 5)

Mouth wash 236 mg/kg 0.27 % 220 mg/kg(n = 5)

* Obtained from: Schweizerisches Lebensmittelbuch, 5th

Edition, Table 8.


Sample Preparation and Remarks

Drinking water To 50 mL add 5 mL TISAB III solution and measure.For this determination, a calibration with concentrations 0.1 and 0.05 mg/Lwas performed. The stir time before measuring is 10 minutes. Fluoride con-tents above 1.5 mg/L can be damaging to the health.

Snow Melt snow. To 50 mL add 5 mL TISAB III solution and measure. For thisdetermination, a calibration with concentrations 0.01 and 0.005 mg/L wasundertaken. The stir time before measuring is 15 minutes.

Mineral water To 50 mL add 5 mL TISAB III solution and measure.

Wine To 50 mL add 5 mL TISAB III solution and measure.

Milk To 50 mL add 5 mL TISAB III solution and measure.Before measuring, the sample was stirred rapidly (75%) for 4 minutes todisperse fat droplets.Remove fat residues from electrode after each measurement.

Table salt Dissolve 20 g table salt in 100 mL deion. water and measure.The same amount of table salt (fluoride free) was added to the calibrationsolutions.

Toothpaste Stir 2.5 g in 50 mL deion. water thoroughly. Add 5 mL TISAB III solutionand measure.Clean electrode after each measurement because the toothpaste sticks to themenbrane. Calibrate prior to each measurement series since the cleaning in-fluences the electrode.

Mouthwash Dilute 10 mL sample with 40 mL deion. water, add 5 mL TISAB III solu-tion and measure.

General Remarks:

1. All measurements were performed using the simple direct method (B).

2. Rinse electrode with deion. water after each measurement and remove clinging water drops witha soft paper tissue.

3. All measurements should be performed using the same stirring conditions. This means the samespeed, stirrer type, distance to electrode etc.

METTLER TOLEDO


M071 Fluoride Determination in Water

Sample: 50 mL drinking water"Schwerzenbach"



Titrant: Fluoride solution 1.0 mg/L

Standard: --

Instruments: METTLER TOLEDO DL70ESHP Deskjet 500 PrinterSample changer ST20A

Method: F00W

Accessories: Titration beaker ME-101974DT120 (temp. sensor Pt100)1 additional burette drive DV901 peristaltic pump



Method F00W Auto.Calib+conc.det of F- 22-Nov-1993 12:49 User aa Measured 22-Nov-1993 13:05

RESULTS


1/1 5*10-5 g/L 50.0 mL pH,pM,pX 4.301 R1 = 175.206 mV Potential 1/2 10-4 g/L 50.0 mL pH,pM,pX 4.000 R1 = 160.647 mV Potential 2/1 Water tap 50.0 mL Fixed volume U R2 = 4.113 pX F- Potential R3 = 0.0772 mg/L F--content 2/2 Water 50.0 mL Fixed volume U R2 = 4.113 pX F- Potential R3 = 0.0772 mg/L F--content 2/3 Water 50.0 mL Fixed volume U R2 = 4.113 pX F- Potential R3 = 0.0772 mg/L F--content 2/4 Water 50.0 mL Fixed volume U R2 = 4.110 pX F- Potential R3 = 0.0777 mg/L F--content

CALIBRATIONSensor F--sensor

Buffer type pH,pM,pX Zero point 0.679 pX0 Slope 48.37 mV/pX Calibration temperature 20.8 °C

STATISTICS Number results R3 n = 4 Mean value x = 0.0773 mg/L F--content Standard deviation s = 0.000254 mg/L F--content Rel. standard deviation srel = 0.329 %


Method Remarks1) The calibration and fluoride concentration de-

termination of each sample is automatically per-formed in a method.

2) The standard solutions 0.1 and 0.05 mg F-/L for thecalibration were made by dispensing fluoride solu-tion (1 mg/L) and TISAB solution into 50 mLdeion. water.

3) Subsequently, the fluoride concentrations of thewater samples are measured. The 5 mL TISAB so-lution were dispensed using the function DIS-PENSE.

4) Between calibration and measurement, the elec-trode is conditioned for 5 minutes in deion. water toprevent contamination with fluoride ions.

5) The measurement requires the following succes-sion of beakers on the sample changer ST20A:

5.1 Two beakers with 50.0 mL deion. water forthe calibration,

5.2 One beaker with deion. water for condition-ing,

5.3 At the end, a beaker with deion. water (redstopper), so that the electrode comes to rest indeion. water (The electrode should not re-main submerged in solutions containing TI-SAB for a long time).

Disposal--

Method F00W Auto.Calib+conc.det of F-

Version 22-Nov-1993 12:49

Title Method ID . . . . . . . . . . . . . F00W Title . . . . . . . . . . . . . Auto.Calib+conc.det of F-

Date/time . . . . . . . . . . . . . 22-Nov-1993 12:49Auxiliary value ID text . . . . . . . . . . . . . . Counter Formula . . . . . . . . . . . . . . H10=1Sample Number samples . . . . . . . . . . 2 Titration stand . . . . . . . . . . ST20 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP ADispense Titrant . . . . . . . . . . . . . . F--solution Concentration [mol/L] . . . . . . . 1.0 Volume [mL] . . . . . . . . . . . . H10*0.251256Dispense Titrant . . . . . . . . . . . . . . TISAB Concentration [mol/L] . . . . . . . 1.0 Volume [mL] . . . . . . . . . . . . (H10*0.0251256)+5.0Stir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 900Measure Sensor . . . . . . . . . . . . . . F--sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 30.0Calculation Result name . . . . . . . . . . . . Potential Formula . . . . . . . . . . . . . . R=E Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mV Decimal places . . . . . . . . . . . 3Calibration Sensor . . . . . . . . . . . . . . . F--sensor Buffer type . . . . . . . . . . . . pH,pM,pX First buffer . . . . . . . . . . 4.301 Second buffer . . . . . . . . . . 4.0 Third buffer . . . . . . . . . . 0.0 Fourth buffer . . . . . . . . . . 0.0 Fifth buffer . . . . . . . . . . 0.0 Sixth buffer . . . . . . . . . . 0.0 Seventh buffer . . . . . . . . . 0.0 Eighth buffer . . . . . . . . . . 0.0 Ri (i=index) . . . . . . . . . . . . R1 Minimal slope . . . . . . . . . . . 40.0 Maximal slope . . . . . . . . . . . 60.0Record Output unit . . . . . . . . . . . . Printer Raw results last sample . . . . . . Yes All results . . . . . . . . . . . . YesConditioning Interval . . . . . . . . . . . . . . 1 Time [s] . . . . . . . . . . . . . . 300Sample Number samples . . . . . . . . . . 4 Titration stand . . . . . . . . . . ST20 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Water Molar mass M . . . . . . . . . . . . 100.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP ADispense Titrant . . . . . . . . . . . . . . TISAB Concentration [mol/L] . . . . . . . 1.0 Volume [mL] . . . . . . . . . . . . 5.0Stir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 600Measure Sensor . . . . . . . . . . . . . . F--sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 30.0Rinse Auxiliary reagent . . . . . . . . . H

2O

Volume [mL] . . . . . . . . . . . . 10.0Calculation Result name . . . . . . . . . . . . Potential Formula . . . . . . . . . . . . . . R2=E[2] Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . pX F-

Decimal places . . . . . . . . . . . 3Calculation Result name . . . . . . . . . . . . F--content Formula . . . . . . . . . . . . . . R3=pw(-R2)*1000 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mg/L Decimal places . . . . . . . . . . . 4Statistics Ri (i=index) . . . . . . . . . . . . R3 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesRecord Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes


Other titratorsDL55+, DL58, DL77 titrators.

Sample Mean / mg/L srel / % Remarksn =

Drinking water 0.0773 0.33 % Sampling:“Schwerzenbach” 4 22.11.93

Drinking water 1.067 0.23 % Sampling:“Basel” 4 3.12.93

(enrichedwith F-)

River water 0.0669 0.51 % Sampling:“Töss” 3 11.10.93

Spring water 0.0748 1.03 % Sampling:“Bachtel” 4 28.11.93


2. Chloride Selective Electrode

Theory The chloride electrode has a solid state membrane composed of a pressed Ag2Sand AgCl composite. The active electrode phase is a nearly water insoluble solidmembrane pasted in the electrode adapter. It is in direct contact with the solutionto be measured.

Measurement range The measurement range of a pressed Ag2S and AgCl composite electrode islimited by the relatively high solubility product of AgCl (2•10-10). Deviationsfrom the Nernst equation are already observed at chloride concentrations under2• 10-5 mol/L.

Using ISA to adjust the ionic strength, linear calibration curves were attainedfrom 1.0 - 5•10-5 mol/L; the detection limit lies somewhat above 10-6 mol/L. Theslope, theoretically calculated from the Nernst equation to be 59.16 mV/pX at25°C, lies at 58-59 mV/pX in practice.

ElectrodesBridge electrolyte The bridge electrolyte for the reference electrode is KNO3 (1 mol/L).

Storage Store electrode dry or in deion. water.

The electrode should not be submerged for long in concentrated chloride-containing solutions because the crystal membrane surface will be damaged.

Handling The solid membrane is sensitive to mechanical impact. Cracks and scratchesrender the electrode useless. Avoid fat deposits on the crystal; do not touch withbare fingers.

Contamination A sluggish or no response indicates that the sensor is contaminated. Deposits onthe crystal can be removed carefully by wiping with a soft tissue.

Repolish non-regenerable modules with an aqueous slurry of aluminum oxide orwith toothpaste. Polishing can shift the electrode zero point by several mV. Thisshift subsides within several days. During this time, however, the electrode mustbe calibrated more frequently.

Reagents

ISA solution: (Ionic Strength Adjustment)

Sodium nitrate solution 5.0 mol/LDissolve 42.5 g sodium nitrate (p.a.) in deion water and adjust to 100 mL in avolumetric flask.

Citrate buffer Dissolve 100 g citric acid p.a. in about 800 mL deion. water.Add 40 g NaOH p.a. (low in chloride) and dissolve. Cool to room temperatureand adjust to 1000 mL. The pH value should be about 5.

Sulfide oxidation Put 62 g boric acid in 800 mL deion water. Add 10 % sodium hydroxide untilsolution the boric acid has dissolved completely and a pH value of 8.5 is reached.

Add 100 mL hydrogen peroxide 30 % and fill to 1000 mL with deion. water.


Cl- stock solution Chloride standard solution (sodium chloride in water) 1.000 g ± 0.002 g Cl- ,MERCK Art. No. 119897. Fill to 1000 mL with deion. water. 1 mL = 1 mgchloride. This solution is used to make appropriate standards.

Remarks

Ionic strength To prevent differences in the ionic strength among samples, add to eachcalibration and measurement solution a constant amount of ISA solution.

Interfering ions Ions that form poorly soluble silver salts, e.g. bromide, iodide, sulfide. Com-plexing agents for silver ions, such as cyanide or thiosulfate, cause falsificationof measured values. The same holds for strong reducing agents. These convertAgCl to metallic silver.

Sulfide containing To prevent the sulfide from interfering with the chloride determination, it mustbe oxidized. All calibration and measurement solutions are mixed 1:1 with thesulfide oxidation solution instead of with the ISA solution. To allow for completesulfide oxidation, let samples stand for 10 minutes before measuring.

Alkaline earth ions Alkaline earth ions can interfere by depositing hydroxide and carbonate on themembrane. This can be prevented by adding citrate buffer 1:1, rather than the ISAsolution.

Extending By mixing 1:1 with e.g. acetone or isopropanol, the AgCl solubility and thus thedetection limit can be lowered and the linear measurement range extended.

Range The same effect is attained by cooling calibration and measurement solutionsbelow room temperature. Combining both methods allows an extension of themeasurement range to < 10-6 mol/L.

Application and Use

Application The chloride electrode is used for chloride determinations in air, water, foods, soiland rock samples.

Use The chloride determination is useful for routine analyses in which the exactcontent is not as interesting as finding a standard or limiting value.

Alternatives Chloride determinations can also be performed using argentometric titration.AgNO3 + Cl- = AgCl + NO3

-

This method is often more selective, more exact and gives more reproducibleresults than the chloride electrode.For these reasons, argentometric titration is frequently used.

Advantages The chloride determination has the following advantages over argentometrictitration:- the determination is faster (with ISE approx. 2 min; titration 3-4 min)- no heavy metal wastes (AgCl)

Disadvantages The chloride determination has the following disadvantages compared toargentometric titration:- not selective for some samples (erroneous results)- poor reproducibility

METTLER TOLEDO


M103 Calibrating the Chloride Electrode

Sample: 50 mL chloride solution1 g/L and 10-2 g/L

Substance: ChlorideM = 35.45 g/mol , z = 1

Preparation: 3 mL ISA solution

Titrant: --

Standard: --

Instruments: METTLER TOLEDO DL77HP Deskjet 500 PrinterMT AT261 Balance

Method: Cl07


Indication: DX235 Chloride ISEDX200 Reference electrode(bridge electrolyte: 1 M KNO3)

Results: METTLER DL77 Titrator V3.0 Mettler-Toledo AG Norma 4766 Market Support Laboratory

Method Cl07 Calibration Cl--Sensor B 19-Aug-1993 8:53 User AS Measured 15-Sep-1993 18:02

RESULTS


1/1 2 50.0 mL pH,pM,pX 2.000 R1 = 232.465 mV Potential 1/2 0 50.0 mL pH,pM,pX 0.000 R1 = 117.808 mV Potential

CALIBRATIONSensor Cl--Sensor B

Buffer type pH,pM,pX Zero point -2.055 pX0 Slope 57.33 mV/pX Calibration temperature 22.1 °C








6) Each measurement requires at leat three min-utes of stirring time for a stable measuredvalue.

Disposal--


Method Cl07 Calibration Cl--Sensor B Version 19-Aug-1993 8:53

Title Method ID . . . . . . . . . . . . . Cl07 Title . . . . . . . . . . . . . Calibration Cl--Sensor B Date/time . . . . . . . . . . . . . 19-Aug-1993 8:53Sample Number samples . . . . . . . . . . 2 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 180Measure Sensor . . . . . . . . . . . . . . Cl--Sensor B Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 30.0Calculation Result name . . . . . . . . . . . . Potential Formula . . . . . . . . . . . . . . R=E Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mV Decimal places . . . . . . . . . . . 3Calibration Sensor . . . . . . . . . . . . . . . Cl--Sensor B Buffer type . . . . . . . . . . . . pH,pM,pX First buffer . . . . . . . . . . 2.0 Second buffer . . . . . . . . . . 0.0 Third buffer . . . . . . . . . . 0.0 Fourth buffer . . . . . . . . . . 0.0 Fifth buffer . . . . . . . . . . 0.0 Sixth buffer . . . . . . . . . . 0.0 Seventh buffer . . . . . . . . . 0.0 Eighth buffer . . . . . . . . . . 0.0 Ri (i=index) . . . . . . . . . . . . R1 Minimal slope . . . . . . . . . . . 55.0 Maximal slope . . . . . . . . . . . 65.0Record Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes

Author: Anke Stock

Typical calibration curve of a chloride selective electrode with ISA solution

METTLER TOLEDO


M104 Chloride Determination with Ion Selective Chloride Electrode

Sample: 50 mL sample solution with1.0 to 0.005 g/L chloride

Substance: ChlorideM = 35.45 g/mol , z = 1

Preparation: 3 mL ISA solution

Titrant: -

Standard: -

Instruments: METTLER TOLEDO DL77Printer (HP Desk Jet 500)

Method: Cl0A, Cl0B




1. For these measurements, aqueous chloride solutions were made with NaCl.

2. The chloride electrode was calibrated daily with 1000 mg/L and 10 mg/L chloride standard .

3. Preparation: Add 3 mL ISA solution to 50 mL sample and measure.

Concentration Recovery srel from several series (n=6 .. 10)mg / L % Method A Method B

1000 100 - 104 % 0.3 - 0.6 % 0.3 - 0.7 %

100 99 - 104 % 0.3 - 0.7 % 0.3 - 0.9 %

10 95 - 108 % 0.2 - 0.3 % 0.3 - 0.5 %

5 107 - 114 % 0.3 - 1.1 % 0.5 - 1.2 %

Result:Method (A) gives a better reproducibility. The differences between (A) and (B) are not, however,decisive in practice.

The concentration 5 mg/L is not in the linear range (see calibration curve page 17). Thus, the range ofuseful concentrations for the chloride electrode is hereafter limited from 1000 to 10 mg/L.


Method A (direct meaurement with mean value)


Method Cl0A Cl--content Version 13-Jul-1993 10:25

Title Method ID . . . . . . . . . . . . . Cl0A Title . . . . . . . . . . . . . Cl--content Date/time . . . . . . . . . . . . . 13-Jul-1993 10:25Sample Number samples . . . . . . . . . . 6 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 180Measure Sensor . . . . . . . . . . . . . . Cl--Sensor B Unit of meas . . . . . . . . . . . . As installed ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Measure Sensor . . . . . . . . . . . . . . Cl--Sensor B Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Measure Sensor . . . . . . . . . . . . . . Cl--Sensor B Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Measure Sensor . . . . . . . . . . . . . . Cl--Sensor B Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Measure Sensor . . . . . . . . . . . . . . Cl--Sensor B Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Measure Sensor . . . . . . . . . . . . . . Cl--Sensor B Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Calculation Result name . . . . . . . . . . . . Potential Formula . . . . . . . . . . . . . . R1=E[1] Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . p(Cl-) Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . Cl--single Formula . . . . . . . . . . . . . . R2=pw(-E[1])*1000 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mg/L Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R3=(C3+E[5]+E[6])/6 Constant . . . . . . . . . . . . . . C3=E[1]+E[2]+E[3]+E[4] Result unit . . . . . . . . . . . . Decimal places . . . . . . . . . . . 3Calculation Result name . . . . . . . . . . . . Cl--x of 6 Formula . . . . . . . . . . . . . . R4=pw(-R3)*1000 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mg/L Decimal places . . . . . . . . . . . 4Statistics Ri (i=index) . . . . . . . . . . . . R2 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesStatistics Ri (i=index) . . . . . . . . . . . . R4 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesRecord Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes

Method B (Single direct measurement)

Remarks


2) Acquisition of six values (six Measure-func-tions) at an interval of at least 10 s.

3) The chloride concentration is calculated fromthe mean of these six values.




Disposal--

Method Cl0B Cl--Content Version 26-Jul-1993 10:35

Title Method ID . . . . . . . . . . . . . Cl0B Title . . . . . . . . . . . . . Cl--Content Date/time . . . . . . . . . . . . . 26-Jul-1993 10:35Sample Number samples . . . . . . . . . . 5 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 180Measure Sensor . . . . . . . . . . . . . . Cl--Sensor B Unit of meas . . . . . . . . . . . . As installed ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R=E Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . p(Cl-) Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . Cl--content Formula . . . . . . . . . . . . . . R2=pw(-E)*1000*f Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . g/L Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . NaCl-content Formula . . . . . . . . . . . . . . R3=R2*1.648 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . g/L

Decimal places . . . . . . . . . . . 5Statistics Ri (i=index) . . . . . . . . . . . . R2 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesStatistics Ri (i=index) . . . . . . . . . . . . R3 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesRecord Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes


Results

Sample Direct measurement with ISE Nominal content Titration with AgNO3(Number) Content srel Producer specification Amount Content

Tomato juice 7.92 g NaCl/L 5.4 % — 2 mL 7.5 g NaCl/L(n = 5)

Tomato ketchup 40.0 g NaCl/kg 1.3 % 33-35 g NaCl/L 2 g 33.0 g NaCl/L(n = 5)

Carrot juice 690 mg Cl-/L 0.7 % 207-771 mg Cl-/L* 25 mL 669 mg Cl-/L(n = 10)

Mayonnaise 12.3 g NaCl/kg 1.0 % 12.3 g NaCl/kg 2 g 11.6 g NaCl/kg(n = 5) ± 3 %

Salad dressing 32.5 g NaCl/kg 1.0 % — 0.5 g 30.9 g NaCl/L(n = 4)

Cheese 12.6 g NaCl/kg 1.5 % — 2 g 13.5 g NaCl/kg(n = 3)

Milk 1.16 g Cl-/L 0.9 % 0.97-1.05 g Cl-/L* 5 mL 1.16 g Cl-/L(n = 5)

Baby food 975 mg NaCl/kg 3.1 % — 10 g 934 mg NaCl/kg(n = 4)

Beans 11.5 g NaCl/kg 5.6 % 8.0 g NaCl/L 5 g 8.4 g NaCl/kgcanned ± 2 g/l(n = 5)

Peas 7.4 g NaCl/kg 1.1 % 8.0 g NaCl/L 5 g 7.4 g NaCl/kgcanned ± 2 g/l(n = 5)

* Obtained from: Schweizerisches Lebensmittelbuch, 5th

Edition, Table 8



Tomato juice Dilute sample with deion. water 1:10. To 50 mL add 3 mL ISA solution andmeasure.Matrix effects cause the somewhat higher values obtained with ISA.

Tomato ketchup Mix 2 g sample with 100 mL deion. water, add 6 mL ISA solution and measure.

Carrot juice Dilute 25 mL sample with 25 mL HNO3 (0.1 mol/L), add 3 mL ISA solution andmeasure.The calibration solutions contained 0.05 mol/L NHO3.

Mayonnaise Dilute 0.5 g sample with 100 mL HNO3 0.1 mol/L, add 6 mL ISA solutionSalad dressing and measure. Higher sample weights are disadvantageous because the risk of fat

adhering to the membrane increases with the amount of fat in solution. This resultsin a poorer slope. The sample was stirred vigorously (70 %) for 4 minutes prior tomeasurement to disperse fat droplets.

The calibration solutions contained 0.05 mol/L NHO3.

Cheese Heat 2.5 g cheese in 100 mL deion. water for 30 minutes with stirring. Aftercooling, adjust volume to 250 mL using HNO3 (0.1 mol/L). To 50 mL add 3 mLISA solution and measure. The sample was stirred more vigorously (70 %) for4 minutes before measuring.

Milk Dilute sample with HNO3 (0.1 mol/L) 1:8. To 100 mL of this add 6 mL ISA so-lution and measure.The sample was stirred more vigorously (70%) for 3 minutes before measuringto disperse fat droplets.The calibration solutions contained 0.05 mol/L NHO3.

Baby food Stir 5 g sample in 100 mL HNO3 (0.1 mol/L), add 6 mL ISA solution and mea-sure.The calibration solutions contained 0.05 mol/L NHO3.

Beans, peas Homogenize can contents with mixer. Stir 10 g resp. 5 g sample into 100 mLcanned deion. water, add 6 mL ISA solution and measure.

General Remarks:

1) All measurements were performed using the simple direct (method B) measurement.

2) Rinse electrode with deion. water after each measurement and remove clinging water drops witha soft paper tissue.

3) All measurements should be performed using the same stirring conditions. This means the samespeed, stirrer type, distance from stirrer to electrode etc.

METTLER TOLEDO


M105 Chloride Determination in Canned Vegetables

Sample: 5 g Peas

Substance: Sodium chloride, NaClM = 35.45 g/mol , z = 1

Preparation: 100 mL deion. water6 mL ISA solution

Titrant: --

Standard: --

Instruments: METTLER TOLEDO DL77HP Deskjet 500 Printer

Method: Cl0C




Method Cl0C NaCl in canned peas 11-Aug-1993 9:53 User AS Measured 11-Aug-1993 10:03

RESULTS


1/1 Cl- 5.3601 g Weight m R1 = 0.6285 p(Cl-) Cl--content R2 = 0.2352 g/L Cl--content R3 = 7.233 g/kg NaCl-content 1/2 Cl- 5.31 g Weight m R1 = 0.6235 p(Cl-) Cl--content R2 = 0.2379 g/L Cl--content R3 = 7.385 g/kg NaCl-content 1/3 Cl- 5.0396 g Weight m R1 = 0.6484 p(Cl-) Cl--content R2 = 0.2247 g/L Cl--content R3 = 7.348 g/kg NaCl-content 1/4 Cl- 5.475 g Weight m R1 = 0.6086 p(Cl-) Cl--content R2 = 0.2463 g/L Cl--content R3 = 7.413 g/kg NaCl-content 1/5 Cl- 5.2528 g Weight m R1 = 0.6248 p(Cl-) Cl--content R2 = 0.2373 g/L Cl--content R3 = 7.444 g/kg NaCl-content

STATISTICS Number results R2 n = 5 Mean value x = 0.2363 g/L Cl--content Standard deviation s = 0.007718 g/L Cl--content Rel. standard deviation srel = 3.266 %

STATISTICS Number results R3 n = 5 Mean value x = 7.364 g/kg NaCl-content Standard deviation s = 0.081698 g/kg NaCl-content Rel. standard deviation srel = 1.109 %



always be at the same temperature. All mea-surements should be performed using the samestirring conditions. This means the samespeed, stirrer type, distance from stirrer to elec-trode etc.

2) Rinse electrode with deion. water after eachmeasurement and remove clinging water dropswith a soft paper tissue.

3) In this method the chloride concentration in g/L (=R2) of the sample solution and the NaClcontent in g/kg (=R3) of the actual sample(canned peas) are calculated.

Sample Preparation1) Purée and homogenize contents of the whole

can.2) Stir 5 g of this with 100 mL deion. water.3) Add 6 mL ISA solution (ISA solution addi-

tion is performed automatically as part ofthe method).

Chloride Determination by Titration with AgNO3

1) 5 g homogenized canned peas are stirred in60 mL deion. water.

2) 2 mL HNO3 (0.1 mol/L) are added and ti-trated with AgNO3 (0.1 mol/L). Electrode:DM141-SC

Result:7.4 g NaCl / kg (n = 2)

Content specified by manufacturer:8 g NaCl / kg ± 2 g/kg

Disposal--

Method Cl0C NaCl in canned peas Version 11-Aug-1993 9:53

Title Method ID . . . . . . . . . . . . . Cl0C Title . . . . . . . . . . . . . NaCl in canned peas Date/time . . . . . . . . . . . . . 11-Aug-1993 9:53Sample Number samples . . . . . . . . . . 5 Titration stand . . . . . . . . . . ST20 1 Entry type . . . . . . . . . . . . . Weight m Lower limit [g] . . . . . . . . . 0.0 Upper limit [g] . . . . . . . . . 15.0 ID1 . . . . . . . . . . . . . . . . Cl-

Molar mass M . . . . . . . . . . . . 35.453 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP ADispense Titrant . . . . . . . . . . . . . . TISAB Concentration [mol/L] . . . . . . . 5.0 Volume [mL] . . . . . . . . . . . . 6.0Stir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 120Measure Sensor . . . . . . . . . . . . . . Cl--Sensor A Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.3 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 3.0 t(max) [s] . . . . . . . . . . . . . 30.0Calculation Result name . . . . . . . . . . . . Cl-content Formula . . . . . . . . . . . . . . R=E Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . p(Cl-) Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . Cl-content Formula . . . . . . . . . . . . . . R2=pw(-R1) Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . g/L Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . NaCl-content Formula . . . . . . . . . . . . . . R3=R2*C3*100/m Constant . . . . . . . . . . . . . . C3=1.648 Result unit . . . . . . . . . . . . g/kg Decimal places . . . . . . . . . . . 3Statistics Ri (i=index) . . . . . . . . . . . . R2 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesStatistics Ri (i=index) . . . . . . . . . . . . R3 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesRecord Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes

Author: Anke Stock

Other titratorsDL55+, DL58, DL70ES Titratoren.


3. Nitrate Selective Electrode

Theory The nitrate electrode is a liquid membrane electrode. This type of electrode worksaccording to the ion exchange principle. The ion to be measured (nitrate) isembedded in an ion exchanger in the PVC polymer membrane. The ion exchang-er is water insoluble and forms a nearly water insoluble complex with the nitrate(e.g. nickel nitrate complex). Therefore, an electrode with a new membrane mustfirst be conditioned for 5 – 10 minutes in a nitrate solution of approx. 0.01 mol/L. This procedure makes the electrode nitrate selective. The insolubility of thenitrate salt allows measurements in aqeous solutions to be performed withoutcausing the nitrate ions to be dissolved out of the active phase. Thus the selectivityis retained.

The active ion substance in the nitrate electrode is an o-phenanthroline-nickel-nitrate complex.

Measurement range When ISA is used to adjust the ionic strength, a linear calibration curve from 0.1- 10-4 mol/L is obtained.

The detection limit lies somewhat above 10-5 mol/L. The slope, theoreticallycalculated from the Nernst equation to be 59.16 mV/pX at 25°C, lies at 58 mV/pX in practice.

Electrodes

Bridging electrolyte As the bridging electrolyte for the reference electrode, a 0.9 mol/L aluminiumsulphate solution (ME-51 340 072) is used. The solution must be renewed daily.

The inner electrolyte (KCl solution, 3 mol/L, ME-51 340 049) is renewedmonthly.

Conditioning The nitrate electrode is conditioned in a nitrate solution, 0.01 mol/L, for 5-10minutes prior to measurement.

Storage Store nitrate electrode dry, preferably in protective sleeve.

Reference electrode: drain electrolyte. To store, seal orifice for filling withrubber stopper. (The longevity of the reference electrode is reduced if thebridging electrolyte chamber is consistently filled up over the inner diaphragm;KCl leakage).

Handling The polymer measurement membrane can be damaged by mechanical impact(e.g. magnetic stirrer, cleaning). If the membrane is damaged, the membranemodule must be replaced. Avoid fat deposits on the membrane; do not touch withbare hands.

Contamination A sluggish response indicates that the sensor is contaminated. Deposits on thesurface of the membrane module can be removed by placing the nitrate electrodein deion. water or dilute acid or base (< 0.001 mol/L) for several minutes. Afterrinsing with deion water, the electrode is conditioned for several minutes inapprox. 0.01 mol/L nitrate solution.

If the electrode is no longer regenerable, the membrane module must be replaced.


Reagents

ISA solution (Ionic Strength Adjustment)

METTLER TOLEDO ISA Aluminum sulfate solution 0.9 mol/L (METTLER TOLEDO 51 340 072)

The ISA solution can also be prepared as it follows.

600 g Al2(SO4)3 • 18 H2O are dissolved in 800 mL deion. water by heating. Aftercooling to room temperature, adjust volume to 1000 mL in flask. The milky,colloidal solution keeps for several weeks at room temp. In case a sedimentdeposits after standing for some time, use only the remaining clear solution bypipetting from the top.

N03- standard Nitrate standard solution 0.1 mol/L:

8.501 g NaNO3, p.a., (eg: Fluka Art. No. 71758) are dissolved in a 1000 mLvolumetric flask in deion. water. Fill to mark. This solution keeps for severalmonths.

HintsIonic strength The total activity of measurement and calibration solutions must be constant. By

adding to each a constant amount of ISA solution, a constant ionic strength isattained.

Interfering ions In order to keep the error induced by interfering ions below 10%, the molarrelation (X- / NO3

- ) of these ions must be smaller than the value in parenthesis:

ClO4- (<0.0007), NO2- (<0.0005), I- (<0.001); Br- (<0.02); Cl- (<1); HS- (<1);

CN- (<0.01); ClO3- (<0.2), HCO3

- (<25); CO3- (<15), PO4

3- , HPO42-, SCN-,

H2PO4-, F- and SO42- (<100)

Anionic tensides should not be present. Chloride, iodide, bromide, phosphate,hydrogensulfite and cyanide can be precipitated with silver sulfate (0.01 mol/L).

Carbonate and bicarbonate can be removed by acidifying with sulfuric acid topH 4.5.

Nitrite is selectively reduced with sulphamic acid.

Org. Acids Many organic acids that interfere with the nitrate electrode are precipitated by thealuminium sulfate in the ISA solution.

Application and Use

Application The nitrate electrode is used for nitrate determination in water, beverages, foods(meat, vegetables), vegetation and fertilizers.

Use The nitrate determination using an ion selective electrode is especially useful forroutine analyses (same samples with known matrix), in which the nitrate contentmust be determined quickly and simply.

Alternatives The nitrate determination can also be achieved using chromatography, photo-metric or potentiometric titration with ferroammonium sulfate.

Advantages - wide application range (0.1 - 10-4 mol/L)- quick, simple determination- no heavy metal wastes (titration)- small investment (compared to chromatography)

Disadvantages - non-selective for a few samples; values are somewhat too high.

METTLER TOLEDO


M106 Calibrating the Nitrate Electrode

Sample: 50 mL nitrate solution10-2 mol/L and 10-4 mol/L

Substance: Nitrate, NO3-

M = 62.00 g/mol , z = 1

Preparation: 5 mL ISA solution(0.9 mol/L Al2(SO4)3 ,ME-51 340 072)

Titrant: --

Standard: --


Method: N007


Indication: DX262 Nitrate ISEDX200 Reference electrode(bridge electrolyte:0.9 mol/L Al2(SO4)3 )


Method N007 Calibration NO3-sensor 28-May-1993 13:42

User AS Measured 02-Jun-1993 8:02

RESULTS


1/1 10-4 mol/L 50.0 mL pH,pM,pX 4.000 R1 = 286.364 mV Potential 1/2 10-2 mol/L 50.0 mL pH,pM,pX 2.000 R1 = 171.847 mV Potential

CALIBRATIONSensor NO

3-Sensor









6) Each measurement requires at least five min-utes stirring time for a stable measured value.(see next page for automatic three point cali-bration).

Disposal--


Method N007 Calibration NO3-sensor

Version 28-May-1993 13:42

Title Method ID . . . . . . . . . . . . . N007 Title . . . . . . . . . . . . . Calibration NO

3-sensor

Date/time . . . . . . . . . . . . . 28-May-1993 13:42Sample Number samples . . . . . . . . . . 2 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 300Measure Sensor . . . . . . . . . . . . . . NO

3-sensor

Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 30.0Calculation Result name . . . . . . . . . . . . Potential Formula . . . . . . . . . . . . . . R=E Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mV Decimal places . . . . . . . . . . . 3Calibration Sensor . . . . . . . . . . . . . . . NO

3-sensor

Buffer type . . . . . . . . . . . . pH,pM,pX First buffer . . . . . . . . . . 4.0 Second buffer . . . . . . . . . . 2.0 Third buffer . . . . . . . . . . 0.0 Fourth buffer . . . . . . . . . . 0.0 Fifth buffer . . . . . . . . . . 0.0 Sixth buffer . . . . . . . . . . 0.0 Seventh buffer . . . . . . . . . 0.0 Eighth buffer . . . . . . . . . . 0.0 Ri (i=index) . . . . . . . . . . . . R1 Minimal slope . . . . . . . . . . . 55.0 Maximal slope . . . . . . . . . . . 65.0Record Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes

Author: Anke Stock

Typical calibration curve of a nitrate selective electrode with ISA solution

METTLER TOLEDO


M107 Automatic Three-point Calibration of the Nitrate Electrode

Sample: 200 mL nitrate solution10-2 , 10-3 and 10-4 mol/Lare prepared automatically


M = 62.00 g/mol , z = 1

Preparation: 20 mL ISA solution(0.9 mol/L Al2(SO4)3 ,ME-51 340 072)

Titrant: Nitrate solution,c(NO3

-) = 10-1 mol/L

Standard: --


Method: N008

Accessories: 250 mL Titr. beaker ME-23515DT120 (temp. sensor Pt100)1 additional burette drive



Method N008 Auto-calibration NO3-sens. 13-Dec-1993 13:53

User aa Measured 13-Dec-1993 13:56

RESULTS


1/1 10-4 mol/L 200.0 mL pH,pM,pX 4.000 R1 = 296.234 mV Potential 1/2 10-3 mol/L 200.0 mL pH,pM,pX 3.000 R1 = 238.805 mV Potential

1/2 10-2 mol/L 200.0 mL pH,pM,pX 2.000 R1 = 182.346 mV Potential

CALIBRATIONSensor NO

3-sensor


AUXILIARY VALUE New value H10 = 1.0 Counter

AUXILIARY VALUE New value H10 = 4.0 Counter


Method Remarks1) Calibration and measurement solutions

should always be at the same temperature.





6) Each measurement requires at least five min-utes stirring time for a stable measured value.

Remarks on method1) The calibration solutions required for this

method (10-2, 10-4 and 10-3 mol/L) were madeautomatically from one nitrate standard solu-tion (10-1 mol/L).

2) Have available exactly 200 mL deion. water.The 20 mL ISA solution and the amount ofnitrate standard solution (10-1 mol/L) are dis-pensed automatically by the titrator.

Disposal--

Other titratorsDL77 titrator.

Method N008 Auto-calibration NO3-sens.

Version 13-Dec-1993 13:53

Title Method ID . . . . . . . . . . . . . N008 Title . . . . . . . . . . . . . Auto-calibration NO

3-sens.

Date/time . . . . . . . . . . . . . 13-Dec-1993 13:53Dispense Titrant . . . . . . . . . . . . . . ISA/NO

3

Concentration [mol/L] . . . . . . . 0.9 Volume [mL] . . . . . . . . . . . . 20Auxiliary value ID text . . . . . . . . . . . . . . Counter Formula . . . . . . . . . . . . . . H10=1.0Sample Number samples . . . . . . . . . . 3 Titration stand . . . . . . . . . . Auto stand Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 200.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP ADispense Titrant . . . . . . . . . . . . . . NO

3-solution

Concentration [mol/L] . . . . . . . 0.1 Volume [mL] . . . . . . . . . . . . 0.2 Condition . . . . . . . . . . . . . Yes Condition . . . . . . . . . . . . H10=1.0Dispense Titrant . . . . . . . . . . . . . . NO

3-solution

Concentration [mol/L] . . . . . . . 0.1 Volume [mL] . . . . . . . . . . . . 2.0 Condition . . . . . . . . . . . . . Yes Condition . . . . . . . . . . . . H10=2.0Dispense Titrant . . . . . . . . . . . . . . NO

3-solution

Concentration [mol/L] . . . . . . . 0.1 Volume [mL] . . . . . . . . . . . . 20.0 Condition . . . . . . . . . . . . . Yes Condition . . . . . . . . . . . . H10=3.0Stir Speed [%] . . . . . . . . . . . . . 70 Time [s] . . . . . . . . . . . . . . 300Auxiliary value ID text . . . . . . . . . . . . . . Counter Formula . . . . . . . . . . . . . . H10=H10+1Measure Sensor . . . . . . . . . . . . . . NO

3-sensor

Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 30.0Calculation Result name . . . . . . . . . . . . Potential Formula . . . . . . . . . . . . . . R=E Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mV Decimal places . . . . . . . . . . . 3Calibration Sensor . . . . . . . . . . . . . . . NO

3-sensor

Buffer type . . . . . . . . . . . . pH,pM,pX First buffer . . . . . . . . . . 4.0 Second buffer . . . . . . . . . . 3.0 Third buffer . . . . . . . . . . 2.0 Fourth buffer . . . . . . . . . . 0.0 Fifth buffer . . . . . . . . . . 0.0 Sixth buffer . . . . . . . . . . 0.0 Seventh buffer . . . . . . . . . 0.0 Eighth buffer . . . . . . . . . . 0.0 Ri (i=index) . . . . . . . . . . . . R1 Minimal slope . . . . . . . . . . . 50.0 Maximal slope . . . . . . . . . . . 60.0Record Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes


METTLER TOLEDO


M108 Nitrate Determination with Ion Selective Electrode

Sample: 50 mL sample solution with100 to 0.01 mmol/L nitrate


M = 62.00 g/mol , z = 1

Preparation: 5 mL ISA solution0.9 mol/L Al2(SO4)3(ME-51 340 072)

Titrant: -

Standard: -


Method: N00A, N00B




1. Aqueous nitrate solutions were used for these measurements. They were prepared from NaNO3,p.a., Fluka Art. No. 71758.

2. The nitrate electrode was calibrated daily with standard solutions of 10 and 0.1 mmol nitrate/L,if necessary already after 2-3 series.

3. Preparation: Add 5 mL ISA solution to 50 mL sample before measuring.

Concentration Recovery srel of several series (n= 6)mmol / L % Method A Method B

100 97 - 102 % 0.33 - 0.8 % 0.41 - 0.8 %

10 99 - 103 % 0.23 - 1.1 % 0.23 - 1.0 %

1 97 - 103 % 0.11 - 0.9 % 0.30 - 1.0 %

0.1 99 - 102 % 0.09 - 1.7 % 0.15 - 1.8 %

0.05 105 - 109 % 0.42 - 0.75 % 0.61 - 0.75 %

0.01 250 - 260 % 0.7 - 3.0 % 0.9 - 3.2 %

ResultThe differences between methods (A) and (B) are not decisive in practice.

The concentration of 0.05 mmol/L is outside the linear range (see calibration curve page 27). Thus, therange of useful concentrations for the nitrate electrode is limited from 100 to 0.1 mmol/L.




Method N00A NO3--content


Title Method ID . . . . . . . . . . . . . N00A Title . . . . . . . . . . . . . NO

3--content

Date/time . . . . . . . . . . . . . 14-Dec-1993 12:59Sample Number samples . . . . . . . . . . 6 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 300Measure

Sensor . . . . . . . . . . . . . . NO3--Sensor

Unit of meas . . . . . . . . . . . . As installed ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Measure

Sensor . . . . . . . . . . . . . . NO3--Sensor

Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Measure

Sensor . . . . . . . . . . . . . . NO3--Sensor


Sensor . . . . . . . . . . . . . . NO3--Sensor


Sensor . . . . . . . . . . . . . . NO3--Sensor


Sensor . . . . . . . . . . . . . . NO3--Sensor

Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Calculation Result name . . . . . . . . . . . . Potential Formula . . . . . . . . . . . . . . R1=E[1] Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . p(NO

3-)

Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . NO

3--single

Formula . . . . . . . . . . . . . . R2=pw(-E[1])*1000 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mmol/L Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R3=(C3+E[5]+E[6])/6 Constant . . . . . . . . . . . . . . C3=E[1]+E[2]+E[3]+E[4] Result unit . . . . . . . . . . . . Decimal places . . . . . . . . . . . 3Calculation Result name . . . . . . . . . . . . NO

3--x of 6

Formula . . . . . . . . . . . . . . R4=pw(-R3)*1000 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mmol/L Decimal places . . . . . . . . . . . 4Statistics Ri (i=index) . . . . . . . . . . . . R2 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesStatistics Ri (i=index) . . . . . . . . . . . . R4 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesRecord Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes


Remarks

Method A1) Stirring during five minutes.






Disposal--

Method N00B NO3--content


Title Method ID . . . . . . . . . . . . . N00B Title . . . . . . . . . . . . . NO

3--content

Date/time . . . . . . . . . . . . . 14-Dec-1993 13:04Sample Number samples . . . . . . . . . . 6 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . NO

3-

Molar mass M . . . . . . . . . . . . 62.00 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 900Measure

Sensor . . . . . . . . . . . . . . NO3--sensor

Unit of meas . . . . . . . . . . . . As installed ∆E [mV] . . . . . . . . . . . . . . 0.3 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 3.0 t(max) [s] . . . . . . . . . . . . . 30.0Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R=E Constant . . . . . . . . . . . . . .

Result unit . . . . . . . . . . . . p(NO3-)

Decimal places . . . . . . . . . . . 4Calculation

Result name . . . . . . . . . . . . NO3--content

Formula . . . . . . . . . . . . . . R2=pw(-E)*1000*f Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mmol/L



Results

Sample Direct measurement with nitrate electrode Number partial samples andmeasurements

n Content srel

Lettuce head 5 2033 mg / kg 1.1 % 1 partial sample, 5 meas’mentssupermarket 15 2149 mg / kg 5.4 % 3 partial samples, 5 meas’ments

Lettuce head 10 1753 mg / kg 0.6 % 5 partial samples, 2 meas’mentsgarden variety

Iceberg lettuce 7 821 mg / kg 1.1 % 1 partial sample, 7 meas’mentsgarden variety 21 924 mg / kg 10.1 % 3 partial samples, 7 meas’ments

Cucumber 6 101 mg / kg 1.5 % 6 partial samples, 1 measurementsupermarket

Potatoes 5 218 mg / kg 1.2 % 1 partial sample, 5 meas’mentssupermarket 9 211 mg / kg 4.5 % 3 partial samples, 3 meas’ments

Spinach 4 969 mg / kg 1.4 % 2 partial samples, 2 meas’mentssupermarket 10 986 mg / kg 6.4 % 5 partial samples, 2 meas’ments

Silver beet 4 117 mg / kg 2.1 % 2 partial samples, 2 meas’mentsorganically grown 10 129 mg / kg 11.3 % 5 partial samples, 2 meas’ments

Cabbage 4 589 mg /kg 5.7 % 2 partial samples, 2 meas’ments10 692 mg / kg 15.4 % 5 partial samples, 2 meas’ments

Carrots 4 215 mg / kg 0.3 % 2 partial samples, 2 meas’mentsorganically grown 8 207 mg / kg 5.2 % 4 partial samples, 2 meas’ments

Carrot juice 10 230 mg / kg 1.8 %

Beet juice 9 2257 mg / kg 0.3 %

Drinking water 3 19 mg / kg 0.6 %

Aquarium water 3 7.2 mg / kg 0.4 %


Sample preparation and remarks

Lettuce head Finely chop whole head with mixer or onion chopper. Mix well. Take 30 gIceberg lettuce (=partial sample) and mix for 1 minute with 370 mL deion. water. Filter through

glass frit. To 50 mL filtrate add 5 mL ISA solution and measure. Tolerance value*lettuce head: 3500 mg / L

Cucumber Finely chop whole cucumber with mixer or onion chopper. Mix well. Take 30 g(=partial sample) and mix for 1 minute with 370 mL deion. water. Filter throughglass frit. To 50 mL filtrate add 5 mL ISA solution and measure.

Potatoes Finely chop 1 kg potatoes with mixer or onion chopper. Mix well. Mix 250 g ofthis (=partial sample) with 250 mL deion. water for 1 minute. Filter through glassfrit. Dilute 25 mL filtrate 1:1 with water, add 5 mL ISA solution and measure.

Spinach Finely chop 500 g sample with mixer or onion chopper. Mix well. Take 30 g.Silver beet (=partial sample) and mix for 1 minute with 370 mL deion. water. Filter through

glass frit. Dilute 25 mL filtrate 1:1 with deion. water, add 5 mL ISA solutionand measure. Tolerance value* spinach: 3500 mg / L

Cabbage Finely chop whole head with mixer or onion chopper. Mix well. Take 30 g of this(=partial sample) and mix for 1 minute with 370 mL deion. water. Filter throughglass frit. Dilute 25 mL filtrate 1:1 with deion. water, add 5 mL ISA solution andmeasure.All cabbage varieties are difficult to measure. They contain sulfur compoundsthat contaminate the membrane and thus reduce the longevity of the electrode.

Carrots Grate 1 kg and mix well.Mix 200 g of this (=partial sample) with 200 mL deion. water for 1 min.Filter through glass frit. Dilute 25 mL filtrate 1:1 with deion. water, add 5 mLISA solution and measure.

Carrot juice Dilute 25 mL sample 1:1 with deion. water.Beet juice Add 5 mL ISA solution and measure.

Producer’s specification for carrot juice: max. 500 mg / LTolerance value* beet juice: 2500 mg / L

Drinking water To 50 mL sample add 5 mL ISA solution and measure.Tolerance value*: 40 mg / L

Aquarium water To 50 mL sample add 5 mL ISA solution and measure.

* Tolerance values indicate the highest allowable concentration of substances. Athigher concentrations, the pertinent authority will intervene. Standing as of Sept1991 (Switzerland).

General remark

All measurements were performed using the simple direct measurement (Method B).

METTLER TOLEDO


M109 Nitrate Determination in Reference Samples

Sample: 2 g Reference sampleBeet (red beet)


M = 62.00 g/mol , z = 1

Preparation: 100 mL deion. water5 mL ISA solution0.9 mol/L Al2(SO4)3(ME-51 340 072)

Titrant: --

Standard: --

Instruments: METTLER TOLEDO DL77HP Deskjet 500 Printer

Method: N00D




Method N00D NO3- dry substance 01-Jul-1993 14:04

User AS Measured 01-Jul-1993 14:07

RESULTS


1/1 beetroot 2.0643 g Weight m R1 = 0.763 mmol/L NO

3--conc

R2 = 4584 mg/kg content dry 1/2 beetroot 2.0643 g Weight m R1 = 0.760 mmol/L NO

3--conc

R2 = 4566 mg/kg content dry 1/3 beetroot 2.0643 g Weight m R1 = 0.766 mmol/L NO

3--conc

R2 = 4599 mg/kg content dry

STATISTICS Number results R2 n = 3 Mean value x = 4583 mg/kg content dry Standard deviation s = 16.48865 mg/kg content dry Rel. standard deviation srel = 0.360 % Outlier test: no outliers!


Method Remarks

Sample Preparation

1) To 2.0 g reference sample are added 100 mLdeion. water. Shake for 1 hour.

2) Filter through folded filter. Dilute 25 mL fil-trate with deion. water 1:1.

3) The sample is ready to be measured. 5 mL ISAare added automatically by the titrator beforemeasuring the potential.

Method


2) Rinse electrode with deion. water after eachmeasurement and remove clinging water dropswith a soft paper tissue.

3) Each measurement requires about 3 minutesstirring time for a stable measured value to beattained.

Disposal--

Method N00D NO3- dry substance

Version 01-Jul-1993 14:04

Title Method ID . . . . . . . . . . . . . N00D Title . . . . . . . . . . . . . NO

3- dry substance

Date/time . . . . . . . . . . . . . 01-Jul-1993 14:04Sample Number samples . . . . . . . . . . 3 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Weight m Lower limit [g] . . . . . . . . . 0.4 Upper limit [g] . . . . . . . . . 4.0 ID1 . . . . . . . . . . . . . . . . beetroot Molar mass M . . . . . . . . . . . . 62.0049 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP ADispense Titrant . . . . . . . . . . . . . . ISA Concentration [mol/L] . . . . . . . 1.0 Volume [mL] . . . . . . . . . . . . 5.0Stir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 180Measure Sensor . . . . . . . . . . . . . . NO

3--sensor

Unit of meas . . . . . . . . . . . . As installed ∆E [mV] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . 10.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 30.0Calculation Result name . . . . . . . . . . . . NO

3--conc

Formula . . . . . . . . . . . . . . R=pw(-E)*1000 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mmol/L Decimal places . . . . . . . . . . . 3Calculation Result name . . . . . . . . . . . . content dry Formula . . . . . . . . . . . . . . R2=R1*M*200/m Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mg/kg Decimal places . . . . . . . . . . .Statistics Ri (i=index) . . . . . . . . . . . . R2 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesRecord Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes


Other titratorsDL53+, DL55+, DL58, DL70ES titrators.

Reference samples (standards)The Swiss Federal Research Institute for Fruit, Wine and Garden Produces in Wädenswil, Switzerland(www.admin.ch/sar/faw) offers reference samples for nitrate determinations. The certified nitratecontent of these samples, which have been mechanically mixed and dried in vacuum over phosphor-pentoxide, was determined using different analysis methods.

ResultsSample n Direct measurement with ISE Content acc. to certificate(Number) Content RSD HPLC GC

Lettuce head 10 27.073 mg/kg 0.2 % 26.600 - 27.300 mg/kg 27.400 - 30.000 mg/kg

Spinach 3 6966 mg/kg 1.2 % 6560 - 6750 mg/kg 6380 - 6540 mg/kg

Cabbage, white 2 8428 mg/kg 1.0 % 7350 - 8440 mg/kg 8680 - 8730 mg/kg

Carrots 3 1545 mg/kg 0.6 % 1390 - 1510 mg/kg 1340 - 1510 mg/kg

Red beet 3 4583 mg/kg 0.4 % 4710 - 4970 mg/kg 4300 - 4730 mg/kg


4. Potassium Selective Electrode

Theory The potassium electrode is a liquid membrane electrode. This type of electrodehas in its membrane a neutral, cyclic organic compound which binds and can thusdetermine cations (such as potassium) due to its structure.The ion active substance in the potassium electrode is the antibiotic valinomycin.Valinomycin shows only a very slight cross reactivity with sodium.

Measurement range When ISA is used to adjust the ionic strength, a linear calibration curve from 0.1– 10-4 mol/L is obtained.The detection limit lies somewhat above 2•10-6 mol/L. The slope, theoreticallycalculated from the Nernst equation to be - 59.16 mV/pK at 25°C, lies at - 58 mV/pK in practice.

ElectrodesBridging electrolyte 0.9 mol/L aluminum sulfate solution (ME-51 340 072), 0.1 mol/L NaCl or

0.1 mol/L TEACl can be used as the bridging electrolyte (TEACl = tetraethylam-moniumchloride). The inner electrolyte (potassium chloride solution, 3 mol/L,ME-51 340 049) should be replaced monthly.

Storage Store the potassium electrode dry (in protective sleeve) or in a dilute potassiumsolution.Reference electrode: drain electrolyte. To store, seal orofice for filling withrubber stopper. (The longevity of the reference electrode is reduced if the bridgingelectrolyte chamber is consistently filled up over the inner diaphragm).

Handling The polymer measurement membrane can be damaged by mechanical impact(e.g. magnetic stirrer, cleaning). If the membrane is damaged, the membranemodule must be replaced.

Contamination A sluggish response indicates that the sensor is contaminated. Deposits on thesurface of the membrane module can be removed by placing the potassiumelectrode in deion. water or dilute acid or base (< 0.001 mol/L) for severalminutes. After rinsing with deion water, the electrode is reconditioned for severalhours in approx. 0.01 mol/L potassium solution.If the electrode is no longer regenerable, the membrane module must be replaced.

ReagentsISA solutions Corresponds with the bridging electrolyte used:

Aluminium sulfate solution 0.9 mol/L (Art. No. 51 340 072) orNaCl solution 5 mol/L orTEACl 10 mol/L (tetraethylammoniumchloride)The ISA solutions can also be freshly made:aluminum sulfate solution 0.9 mol/L:Dissolve 600 g Al2(SO4)3 • 18 H2O in 600 mL deion. water while warming. Coolto room temp. and adjust volume to 1000 mL. The milky colloidal solution keepsfor several weeks at room temp. Should a sediment form upon standing for sometime, use the remaining clear solution by pipetting off the top.NaCl solution 5 mol/L:Dissolve 29.22 g NaCl p.a. in 80 mL deion. water in a volumetric flask andfill to 100 mL.


K+ standard Potassium standard solution 1000 mg/L:potassium standard solution (KCl in water) 1.000 g ± 0.002 g , e.g. fromMERCK No. 109924or weigh 1.907 g KCl, p.a. MERCK No. 104936 into a 1000 mL volumetricflask, fill with deion. water to mark.This solution keeps for several months.

Hints

Ionic strength The total activity of measurement and calibration solutions must be constant. Byadding to each a constant amount of ISA solution, a constant ionic strength isattained.

Interfering ions In order to keep the error induced by interfering ions below 10 %, the molarrelation (X- / K+ ) of these ions must be smaller than the value in parenthesis:

Rb+ (<0.005), Cs+ (<0.02), NH4+ (<1), Sr+2 (<20), Ca+2 (<500),H+ (<1000), Na+ (<2000), Mg+2 (<2000)Cationic tensides should not be present.

Ammonium: can be removed by boiling at pH 12 (with NaOH). Cool andneutralize prior to measuring.

Application and Use

Application The potassium electrode is used for potassium determination in water, bever-ages, serum, infusion solutions, soil samples and fertilizers.

Use The potassium determination using an ion selective electrode is especiallyuseful for routine analyses (same samples with known matrix), in which thepotassium content must be determined quickly and simply.

Alternatives The potassium determination can also be performed using ion chromatography,flame photometry or atomic absorption.

For higher concentrations,i.e. > 10-3 mol/L, potentiometric titration using sodi-um tetraphenylborate (Na-TPB) is possible.

Advantages - wide application range (0.1 – 10-4 mol/L)- rapid and simple determination- smaller investment (compared to ion chromatography or atomic absorption)

Disadvantages - pH sensitive

METTLER TOLEDO


M110 Calibration of the Potassium Electrode

Sample: 50 mL potassium solution1 g/L and 10-2 g/L

Substance: Potassium, K+

M = 39.0983 g/mol , z = 1

Preparation: 1 mL ISA solution(5 mol/L NaCl solution)

Titrant: --

Standard: --


Method: K007


Indication: DX239 Potassium ISEDX200 Reference electrode(bridge electrolyte:0.9 mol/L Al2(SO4)3 )


Method K007 Calibration K+-sensor 04-Jan-1994 9:16 User aa Measured 04-Jan-1994 9:18

RESULTS


1/1 0.01 g/L 50.0 mL pH,pM,pX 2.000 R1 = 39.969 mV Potential 1/2 1 g/L 50.0 mL pH,pM,pX 0.000 R1 = 152.177 mV Potential

CALIBRATIONSensor K+-Sensor

Buffer type pH,pM,pX Zero point 2.712 pX0 Slope -56.10 mV/pX Calibration temperature 20.1 °C








6) Each measurement requires 5 minutes stirringtime for a stable measured value.

7) For three-point calibration with automatic pro-duction of the standard solutions, a methodsimilar to the one for the nitrate ISE can beused (page 29).

Disposal--


Method K007 Calibration K+-sensor Version 04-Jan-1994 9:16

Title Method ID . . . . . . . . . . . . . K007 Title . . . . . . . . . . . . . Calibration K+-sensor Date/time . . . . . . . . . . . . . 04-Jan-1994 9:16Sample Number samples . . . . . . . . . . 2 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 39.0983 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 300Measure Sensor . . . . . . . . . . . . . . K+-sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 30.0Calculation Result name . . . . . . . . . . . . Potential Formula . . . . . . . . . . . . . . R=E Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mV Decimal places . . . . . . . . . . . 3Calibration Sensor . . . . . . . . . . . . . . . Na+-sensor Buffer type . . . . . . . . . . . . pH,pM,pX First buffer . . . . . . . . . . 2.0 Second buffer . . . . . . . . . . 0.0 Third buffer . . . . . . . . . . 0.0 Fourth buffer . . . . . . . . . . 0.0 Fifth buffer . . . . . . . . . . 0.0 Sixth buffer . . . . . . . . . . 0.0 Seventh buffer . . . . . . . . . 0.0 Eighth buffer . . . . . . . . . . 0.0 Ri (i=index) . . . . . . . . . . . . R1 Minimal slope . . . . . . . . . . . -45.0 Maximal slope . . . . . . . . . . . -65.0Record Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes


Typical calibration curve of a potassium selective electrode with ISA solution

METTLER TOLEDO


M111 Potassium Determination with Ion Selective Electrode

Sample: 50 mL Sample solution with1000 to 1 mg/L potassium

Substance: Potassium, K+

M = 39,0983 g/mol , z = 1

Preparation: 1 mL ISA solution(5 mol/L NaCl)

Titrant: -

Standard: -


Method: K00A, K00B


Indication: DX239 Potassium ISEDX200 Reference electrode(bridge electrolyte:0.9 mol/L Al2(SO4)3 )


1. Aqueous potassium solutions were used for these measurements. They were made from thepotassium standard 1.000 ± 0.002 g K+ (MERCK Art. No. 109924).

2. The potassium electrode was recalibrated daily with standard solutions 1.0 and 0.01 g K+/L, ifnecessary after 2-3 series.

3. The potassium and reference electrodes were stored in dilute potassium solution (0.001 g/L)before and between measurements.

Concentration Recovery RSD of several series (n= 6)mmol / L % Method A Method B

1000 97 - 103 % 0.3 - 1.0 % 0.4 - 1.0 %

100 98 - 103 % 0.2 - 1.4 % 0.3 - 1.4 %

10 99 - 102 % 0.3 - 1.2 % 0.4 - 1.3 %

5 98 - 102 % 0.3 - 0.8 % 0.4 - 0.7 %

1 110 - 115 % 1.1- 4.2 % 1.2 - 4.2 %

ResultThe differences between methods (A) and (B) are not decisive in practice.

The concentration 0.001 mg/L is not in the linear range (see calibration curve page 39). Thus, the rangeof useful concentrations for the potassium electrode was limited from 1000 to 5 mg/L.


Method A (direct measurement with mean value)


Method K00A K+-content Version 04-Jan-1994 9:49

Title Method ID . . . . . . . . . . . . . K00A Title . . . . . . . . . . . . . K+-content Date/time . . . . . . . . . . . . . 04-Jan-1994 9:49Sample Number samples . . . . . . . . . . 6 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 300Measure

Sensor . . . . . . . . . . . . . . K+-Sensor Unit of meas . . . . . . . . . . . . As installed ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Measure

Sensor . . . . . . . . . . . . . . K+-Sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Measure




Sensor . . . . . . . . . . . . . . K+-Sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R1=E[1] Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . p(K+) Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . K+-single Formula . . . . . . . . . . . . . . R2=pw(-E[1])*1000 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mg/L Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R3=(C3+E[5]+E[6])/6 Constant . . . . . . . . . . . . . . C3=E[1]+E[2]+E[3]+E[4] Result unit . . . . . . . . . . . . Decimal places . . . . . . . . . . . 3Calculation Result name . . . . . . . . . . . . K+-x of 6 Formula . . . . . . . . . . . . . . R4=pw(-R3)*1000 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mg/L Decimal places . . . . . . . . . . . 4Statistics Ri (i=index) . . . . . . . . . . . . R2 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesStatistics Ri (i=index) . . . . . . . . . . . . R4 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesRecord Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes


Remarks

Method A1) Stirring during five minutes.






Disposal--

Method K00B K+-content Version 04-Jan-1994 9:09

Title Method ID . . . . . . . . . . . . . K00B Title . . . . . . . . . . . . . K+-content Date/time . . . . . . . . . . . . . 04-Jan-1994 9:09Sample Number samples . . . . . . . . . . 6 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . K+

Molar mass M . . . . . . . . . . . . 39.0983 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 300Measure

Sensor . . . . . . . . . . . . . . K+-sensor Unit of meas . . . . . . . . . . . . As installed ∆E [mV] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 30.0 t(max) [s] . . . . . . . . . . . . . 60.0Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R=E Constant . . . . . . . . . . . . . .

Result unit . . . . . . . . . . . . p(K+) Decimal places . . . . . . . . . . . 4Calculation

Result name . . . . . . . . . . . . K+-content Formula . . . . . . . . . . . . . . R2=pw(-E)*1000*f Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mg/L



Results

Sample Dilution Direct measurement with potassium electrode Content

n Mean value srel (Producer spec.)

Milk 1:20 6 1557 mg/L 0.36 % 1.6 -1.9 g/L *

Orange juice 1:20 6 1698 mg/L 0.12 % 1.4 - 2.7 g/L*

Apple juice 1:20 6 973 mg/L 0.12 % 0.9 - 1.5 g/L*

Grape juice, red 1:20 6 1219 mg/L 0.24 % 0.9 - 2.2 g/L*

Wine, red 1:10 6 739 mg/L 0.34 % 0.4 - 1.6 g/L*Italian

Wine, white 1:10 6 764 mg/L 0.20 % 0.4 - 1.6 g/L*Swiss

Carrot juice 1:50 6 3076 mg/L 0.29 % 1.5 - 3.4 g/L*freshly pressed

Beet juice ** 1:50 6 2745 mg/L 0.22 % —with sour whey

Beet juice ** 1:50 6 3588 mg/L 0.33 % 3.2 - 7.2 g/L*org. grown

Beet juice ** 1:50 6 4575 mg/L 0.40 % 3.2 - 7.2 g/L*wholesale

Elderberry juice 1:50 5 3739 mg/L 0.17 % 4.4 - 5.3 g/L*70% fruit flesh

Infusion solution 1:5 3 200.8 mg/L 0.20 % 199.2 mg/L

Liquid fertilizer 1:400 4 26.69 g/L 0.30 % 26.6 g/L

Garden soil 1:1 3 33.6 mg/kg 0.29 % —-from garden

Potting soil 1:2 4 496 mg/kg 0.26 % 290-440 mg/kgpurchased

* Obtained from: Schweizerisches Lebensmittelbuch

** Beet = red beet



General Potassium is important for cell metabolism and for maintenance of the potas-sium / sodium equilibrium. Excess potassium is excreted by the body, unlikesodium. Thus, excess sodium can result in such a shift of the equilibrium infavor of sodium that even with normal potassium values, a potassium deficien-cy may show up.

Potassium deficiency may lead to muscle weakness and tightness, an irregularheart rhythm, high pulse rates, oedemas and frequently to cramps, especially ofthe rear and leg muscles.

Beverages Are diluted 1:10 to 1:50, depending on the potassium content. To 50 mL dilutedsample are added 1 mL ISA solution before measuring.

Infusion solution Dilute sample 1:5. To 50 mL add 0.5 mL ISA solution and measure. Less ISAsolution is used for this sample as it already contains NaCl.

Fertilizer Dilute sample 1: 400. To 50 mL add 1 mL ISA solution and measure.

Garden soil Dry overnight at 170 – 180°C. Extraction: to 149 g add 200 mL deion. water,mix with mixer for 1 minute, let settle for 2 hours. Vacuum filter. To 50 mLfiltrate add 1 mL ISA solution and measure.

Potting soil Dry overnight at 170 – 180°C. Extraction: to 149 g add 400 mL deion. water,mix with mixer for 1 minute, let settle for 4 hours. Vacuum filter. To 50 mLfiltrate add 1 mL ISA solution and measure.

General remarks:

1) All measurements were performed using the simple direct measurement (method B).




5. Sodium Selective Electrode

Theory The sodium electrode is a glass electrode. pH glass electrodes show a negligiblealkali error. Amplification of the “alkali error” leads to sodium selectiveelectrodes which respond only to changes in the sodium ion concentration at pHvalues above 7. Besides glass membranes, gel membranes can also be used forthe sodium determination. The ion active substance is the antibiotic actino-mycene.

Measurement range When ISA is used to adjust the ionic strength and the pH value (over pH 7), alinear calibration curve from 0.1 – 10-4 mol/L is obtained. The detection limit liesaround 5•10-6 mol/L. The slope, theoretically calculated from the Nernst equa-tion to be - 59.16 mV/pNa at 20°C, lies at - 58 mV/pNa in practice.

Electrodes

Bridging electrolyte 0.1 mol/L ammonium chloride, NH4Cl, is used as bridging electrolyte for the

reference electrode.

Conditioning Condition new sodium electrode overnight in a concentrated NaCl solution.

Storage Store sodium electrode with the glass membrane in 0.1 mol/L NaCl solution.

Reference electrode: drain electrolyte. To store, seal orifice for filling withrubber stopper. (The longevity of the reference electrode is reduced if thebridging electrolyte chamber is consistently filled up over the inner diaphragm).

Contamination A sluggish response or too small slope (>52 mV/pNa) indicates that the sensoris contaminated. Deposits on the surface of the glass membrane can be removedby cleaning with the usual lab cleansers. After each treatment, rinse electrodewith deion water and conditioned for several hours in a concentrated sodiumsolution.

Reagents

ISA solution Ionic Strength Adjustment:basic ammonium chloride solution or triethanolamine solution.

Production Basic ammonium chloride solution (4 m NH4Cl and 1 m NH4OH):dissolve 213 g NH4Cl and 140 g NH4OH 25 % in 800 mL deion. water. Adjustvolume to 1000 mL using volumetric flask.Triethanolamine solution:Dissolve 74.6 g triethanolamine in 800 mL deion. water, adjust to pH 10.2 withHCl. Fill volumetric flask to 1000 mL mark.

Na+ standard Sodium standard solution 1000 mg/L:Sodium standard solution (NaCl in water) 1.000 g ± 2 mg MERCK No. 109927fill to 1000 mL with deion water in a volumetric flask.This solution keeps forseveral months.Sodium standard solution 0.1 mol/L:Dissolve 5.844 g NaCl (titrimetric standard) in 800 mL deion. water and fill to1000 mL in volumetric flask.


Hints

Ionic strength The total activity of sample and calibration solutions must be constant. The pHvalue must be over 7. By adding to each sample a constant amount of ISAsolution, a constant ionic strength is attained.

Interfering ions In order to keep the error induced by interfering ions below 10 %, the molarrelation (X- / Na+ ) of these ions must be smaller than the value in parenthesis:

H+ (<0.001), Li+ (<1), K+ (<5), NH4+ (<50), Mg+2 (<2000)

Silver ions Ag+ should not be present.

Application and Use

Application The sodium electrode is used for sodium determination in water, beverages, dietfoods, serum, soil samples and glass.

Use The sodium determination using an ion selective electrode is especially useful forroutine analyses (same samples with known matrix), in which the sodium contentmust be determined quickly and simply.

Alternatives The sodium determination can also be performed using flame photometry oratomic absorption. A sodium content determination via titration is possible onlyindirectly by chloride determination, provided that Na is present as NaCl.

Advantages - wide application range (0.1 - 10-4 mol/L)- the determination is rapid and simple

Disadvantages - pH value sensitive

METTLER TOLEDO


M112 Calibration of the Sodium Electrode

Sample: 50 mL sodium-containing sol’n0.1 mol/L and 10-3 mol/L

Substance: Sodium, Na+

M = 22.99 g/mol , z = 1

Preparation: 1 mL ISA solution(4 mL NH4Cl and 1 ml NH4OH)

Titrant: --

Standard: --


Method: Na07


Indication: DX223 Sodium ISEDX200 Reference electrode(bridge electrolyte: 0.1 M NH4Cl)

Results: METTLER DL77 Titrator V3.0 Mettler-Toledo AG Market Support Laboratory

Method Na07 Calibration Na+-sensor 16-Mar-1994 12:45 User aa Measured 16-Mar-1994 13:08

RESULTS


1/1 Na+ 10-3 mol/L 50.0 mL pH,pM,pX 3.000 R1 = 155.957 mV Potential 1/2 Na+ 10-1 mol/L 50.0 mL pH,pM,pX 1.000 R1 = 271.455 mV Potential

CALIBRATIONSensor Na+-Sensor

Buffer type pH,pM,pX Zero point 5.701 pX0 Slope -57.75 mV/pX Calibration temperature 21.9 °C








6) Each measurement requires 10 minutes stir-ring time for a stable measured value.

7) For three-point calibration with automatic pro-duction of the standard solutions, a methodsimilar to the one for the nitrate ISE can beused (page 28).

Disposal--


Method Na07 Calibration Na+-sensor Version 16-Mar-1994 12:45

Title Method ID . . . . . . . . . . . . . Na07 Title . . . . . . . . . . . . . Calibration Na+-sensor Date/time . . . . . . . . . . . . . 16-Mar-1994 12:45Sample Number samples . . . . . . . . . . 2 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Na+

Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 600Measure Sensor . . . . . . . . . . . . . . K+-sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 2.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 30.0 t(max) [s] . . . . . . . . . . . . . 60.0Calculation Result name . . . . . . . . . . . . Potential Formula . . . . . . . . . . . . . . R=E Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mV Decimal places . . . . . . . . . . . 3Calibration Sensor . . . . . . . . . . . . . . . Na+-sensor Buffer type . . . . . . . . . . . . pH,pM,pX First buffer . . . . . . . . . . 3.0 Second buffer . . . . . . . . . . 1.0 Third buffer . . . . . . . . . . 0.0 Fourth buffer . . . . . . . . . . 0.0 Fifth buffer . . . . . . . . . . 0.0 Sixth buffer . . . . . . . . . . 0.0 Seventh buffer . . . . . . . . . 0.0 Eighth buffer . . . . . . . . . . 0.0 Ri (i=index) . . . . . . . . . . . . R1 Minimal slope . . . . . . . . . . . -45.0 Maximal slope . . . . . . . . . . . -65.0Record Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes


Typical calibration curve of a sodium selective electrode with ISA solution

METTLER TOLEDO


M113 Sodium Determination with Ion Selective Electrode

Sample: 50 mL Sample solution with0.1 to 0.001 mol/L sodium

Substance: Sodium, Na+

M = 22.99 g/mol , z = 1

Preparation: 1 mL ISA solution(4 mL NH4Cl and 1 ml NH4OH)

Titrant: -

Standard: -


Method: Na0A, Na0B


Indication: DX223 Sodium ISEDX200 Reference electrode(bridge electrolyte: 0.1 M NH4Cl)


1. Aqueous sodium solutions were used for these measurements. They were made from NaCl(titrimetric standard).

2. The sodium electrode was recalibrated daily with standard solutions 0.1 and 0.001 g Na+/L.

3. The sodium electrode was stored in a concentrated sodium solution.

4. Preparation: Add 1 mL ISA solution to 50 mL sample before measuring. The solutions wereproduced fresh daily.

Concentration Recovery srel of several series (n= 6)mmol / L % Method A Method B

0.1 98 - 102 % 0.2 - 0.5 % 0.2 - 0.6 %

0.01 95 - 100 % 0.2 - 0.6 % 0.3 - 0.7 %

0.001 97 - 101 % 0.2 - 0.8 % 0.2 - 0.9 %

0.0005 101 - 106 % 0.2 - 0.4 % 0.2 - 0.5 %

0.0001 131 - 129 % 0.2 - 0.9 % 0.2 - 0.9 %

ResultThe differences between methods (A) and (B) are not decisive in practice.At concentrations under 0.001 mol/L, longer stir times (15 – 20 minutes) were necessary to attain a goodreproducibility.

The concentration 0.0001 mol/L is not in the linear range (see calibration curve page 47). Thus, therange of useful concentrations for the sodium electrode was limited from 0.1 mol/L to 0.001 mol/L.




Method Na0A Na+-content Version 15-Mar-1994 19:48

Title Method ID . . . . . . . . . . . . . Na0A Title . . . . . . . . . . . . . Na+-content Date/time . . . . . . . . . . . . . 15-Mar-1994 19:48Sample Number samples . . . . . . . . . . 6 Titration stand . . . . . . . . . . Stand 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 0.0 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 600Measure

Sensor . . . . . . . . . . . . . . Na+-Sensor Unit of meas . . . . . . . . . . . . As installed ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Measure

Sensor . . . . . . . . . . . . . . Na+-Sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Measure




Sensor . . . . . . . . . . . . . . Na+-Sensor Unit of meas . . . . . . . . . . . . mV ∆E [mV] . . . . . . . . . . . . . . 0.2 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 10.0 t(max) [s] . . . . . . . . . . . . . 90.0Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R1=E[1] Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . p(Na+) Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . Na+-single Formula . . . . . . . . . . . . . . R2=pw(-E[1])*1000 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mmol/L Decimal places . . . . . . . . . . . 4Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R3=(C3+E[5]+E[6])/6 Constant . . . . . . . . . . . . . . C3=E[1]+E[2]+E[3]+E[4] Result unit . . . . . . . . . . . . Decimal places . . . . . . . . . . . 3Calculation Result name . . . . . . . . . . . . Na+-x of 6 Formula . . . . . . . . . . . . . . R4=pw(-R3)*1000 Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mmol/L Decimal places . . . . . . . . . . . 4Statistics Ri (i=index) . . . . . . . . . . . . R2 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesStatistics Ri (i=index) . . . . . . . . . . . . R4 Standard deviation s . . . . . . . . Yes Rel. standard deviation srel . . . . Yes Outlier test . . . . . . . . . . . . YesRecord Output unit . . . . . . . . . . . . Printer All results . . . . . . . . . . . . Yes


Remarks



3) The sodium concentration is calculated fromthe mean of these six values.

Method B1) Stirring during five minutes.



Disposal--

Method Na0B Na+-content Version 22-Mar-1994 13:07

Title Method ID . . . . . . . . . . . . . Na0B Title . . . . . . . . . . . . . Na+-content Date/time . . . . . . . . . . . . . 22-Mar-1994 13:07Sample Number samples . . . . . . . . . . 6 Titration stand . . . . . . . . . . ST20 1 Entry type . . . . . . . . . . . . . Fixed volume U Volume [mL] . . . . . . . . . . . 50.0 ID1 . . . . . . . . . . . . . . . . Molar mass M . . . . . . . . . . . . 22.99 Equivalent number z . . . . . . . . 1 Temperature sensor . . . . . . . . . TEMP AStir Speed [%] . . . . . . . . . . . . . 50 Time [s] . . . . . . . . . . . . . . 300Measure

Sensor . . . . . . . . . . . . . . Na+-sensor Unit of meas . . . . . . . . . . . . As installed ∆E [mV] . . . . . . . . . . . . . . 0.5 ∆t [s] . . . . . . . . . . . . . . 5.0 t(min) mode . . . . . . . . . . . . Fix t(min) [s] . . . . . . . . . . . 60.0 t(max) [s] . . . . . . . . . . . . . 120.0Calculation Result name . . . . . . . . . . . . Formula . . . . . . . . . . . . . . R=E Constant . . . . . . . . . . . . . .

Result unit . . . . . . . . . . . . p(Na+) Decimal places . . . . . . . . . . . 3Calculation

Result name . . . . . . . . . . . . Na+-content Formula . . . . . . . . . . . . . . R2=pw(-E)*1000*f Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mmol/L Decimal places . . . . . . . . . . . 2Calculation

Result name . . . . . . . . . . . . Na+-content Formula . . . . . . . . . . . . . . R3=R2*M Constant . . . . . . . . . . . . . . Result unit . . . . . . . . . . . . mg/L



Results

Sample Dilution Direct measurement with Na electrode Contentn Mean value srel Producer spec.

Milk, full cream 1:10 6 400.8 mg/L 0.20 % 430 -490 mg/L *pasteurized

Milk, full cream 1:10 6 433.8 mg/L 0.20 % 430 -490 mg/L *raw

Apple juice none 4 8.2 mg/L 0.64 % < 30 mg/L*

Grape juice,red none 5 23.8 mg/L 0.66 % < 30 mg/L*

Wine, red none 5 12.2 mg/L 0.63 % 10 - 80 mg/L*Italian

Wine, white none 5 8.4 mg/L 2.0 % 10 - 80 mg/L*Swiss

Mineral water none 6 8.17 mg/L 0.22 % 8.2 mg/L

Drinking water none 5 3.81 mg/L 0.35 % —Schwerzenbach

Bouillon 1:20 5 468.5 mg/L 0.35 % < 1.2 g/Lsodium reduced

Bouillon 1:50 5 4110 mg/L 0.41 % ~ 4 g/Lnormal

Herb paté 1:8 6 175.9 mg/kg 0.52 % < 0.4 g/kgsodium reduced

Infusion solution 1:100 5 142.5 mmol/L 0.72 % 141.5 mmol/L

* Obtained from: Schweizerisches Lebensmittelbuch



General Sodium influences cell metabolism. The body cannot get rid of excess sodium.Therefore, a sodium excess shifts the sodium / potassium equilibrium to thedisadvantage of potassium.

A high blood pressure requires a diet low in sodium.

Milk Dilute sample 1:10. To 50 mL of this add 1 mL ISA solution and measure.

Apple juice To 50 mL undiluted sample add 1 mL ISA solution and 1.5 mL NH4OH 5 %and measure. The pH of the sample is adjusted to pH 7.5 with the excessNH4OH. (For correct measurement with the sodium electrode, the pH must beover 7.)

Wine, grape juice To 50 mL undiluted sample add 1 mL ISA solution and 1.5 mL NH4OH 5 %and measure. The pH of the sample is adjusted to pH 8 with the excess NH4OH.(For correct measurement with the sodium electrode, the pH must be over 7.)

Mineral water To 50 mL undiluted sample add 1 mL ISA solution and measure.

Drinking water To 50 mL undiluted sample add 1 mL ISA solution and measure.

Due to the low sodium content, the standards 10-3 and 10-4 mol/L were used forcalibration for this sample.

Bouillon Place a bouillon cube in 300 mL deion. water and warm till it has dissolved. Letcool and use deion. water to adjust volume to 500 mL. Dilute this solution 1:20resp. 1:50 with deion. water. To 50 mL add 1 mL ISA solution and measure.

Herb paté Mix entire contents of can (125 g) with 700 mL deion. water for about5 minutes. Decant fat. Fill to 1000 mL with deion. water. To 50 mL of this add1 mL ISA solution and measure.

Infusion solution Dilute sample 1:100 and to 50 mL of this add 1 mL ISA solution and measure.

General remarks:

1) All measurements were performed using the simple direct measurement (method B).




6. Troubleshooting

Completely wrong measured values:Instrument defective. Test with short circuit plug.

Bad contact to electrode plug. Plug in and out a few times.

Reference electrode empty. Fill with electrolyte, control ground joint.

Ground joint diaphragm dried out. Open joint, let electrolyte flow out andclose joint firmly.

Unstable measured value:Instrument defective. Test with short circuit plug.

Bad contact to electrode plug. Plug in and out a few times.

No ISA solution. Add ISA solution.

Larger air bubble in electrode. Shake vigorously (like a fever thermometer).

Electrode body defective. Replace.

Reference electrode contaminated or defective.Clean or replace reference electrode

Insufficient slope:Calibration solution contaminated or Make new calibration solutions.incorrectly diluted.


Membrane module screwed in too Screw in membrane module tightly.loosely.

Membrane contaminated. Clean or replace membrane module.

Larger air bubble in electrode. Shake vigorously once toward electrode head(like a fever thermometer).

Electrode not conditioned long enough. Condition in dilute solution of theselective ion, approx. 0.001mol/L.(For Na electrode use conc. NaCl solution)

Bridging electrolyte leaked out of the Refill with bridging electrolyte and close groundreference electrode. joint firmly.


Drift in display (sluggish response):Temperature not constant. Use thermostat.


Membrane contaminated. Clean or replace membrane module.

Electrode not conditioned long enough. Condition in dilute solution of theselective ion, approx. 0.001mol/L.(For Na electrode use conc. NaCl solution)

Reference electrode contaminated or defective.Clean or replace reference electrode.

Wrong bridging electrolyte. Replace with correct bridging electrolyte andclose ground joint firmly.

Measurement membrane exhausted Replace membrane module.(Na-ISE: replace electrode).

Content too low:Too much time or too many measurements Recalibrate, at least once a day.since last calibration.

Calibration solution contaminated or Make new calibration solutions.incorrectly diluted.

No ISA solution in samples. Add ISA solution.

Incorrect pH value of sample solutions. Control sample pH value.correct pH value, i.e.: with ISA or buffer solutions(For Na electrode use ammonium to adjust pH > 7).

Ions to be determined partially complexed. Standard addition instead of direct measurement,add ISA solution.

Content too high:Too much time or too many measurements Recalibrate, at least once a day.since last calibration.

Calibration solution contaminated or Make new calibration solutions.incorrectly diluted.

Concentration of interfering ions too high. Eliminate interfering ions (precipitate, complex).

Concentration too low or outside the Dilute less.calibration range (measurement in the Recalibrate with standards near the samplenon-linear range). concentration.


7. Summary of the Ion Selective Electrodes and ReagentsUsed

Electrode Name Type Lin. meas’ment range Lower limit Interfering ions

Fluoride DX219 Solid state 1 - 10-6 mol/L 0.01 ppm OH-

membrane

Chloride DX235 Solid state 1 - 10-4 mol/L 2 ppm no Br-, I-, CN-,membrane S-2

Nitrate DX262 PVC 1 - 10-5 mol/L 0.1 ppm Br-, I-, F-, Cl-, NO2-

membrane ClO4-, ClO3-, HS-,CN-, SO4-2, PO4-3,CO3-, SCN-

no anion. tensides

Potassium DX239 PVC 1- 10-4 mol/L 0.1 ppm Na+, Rb+, Cs+,membrane Ca+2, Mg+2, NH4+

no cation. tensides

Sodium DX223 Glass 0.1 - 10-4 mol/L 25 ppm Li+, K+, NH4+,electrode Mg+2, no Ag+


pH ISA solutions Reference electroderange Type Inner electrol. Bridging electrolyte

5 - 8 TISAB 3 DX200* KCl 3 mol/L KNO3 1 mol/L

2 -11 NaNO3 5 mol/L DX200 KCl 3 mol/L KNO3 1 mol/L

3 - 10 Al2(SO4)3 0.9 mol/L DX200 KCl 3 mol/L Al2(SO4)3 0.9 mol/L

4 - 9 Al2(SO4)3 0.9 mol/L DX200 KCl 3 mol/L Al2(SO4)3 0.9 mol/L

NaCl 5 mol/L KCl 3 mol/L NaCl 0.1 mol/L

TEACl** 10 mol/L KCl 3 mol/L TEACl** 0.1 mol/L

7 - 10 NH4Cl 4 mol/L + DX200 KCl 3 mol/L NH4Cl 0.1 mol/LNH4OH 1 mol/L

Triethanolamine 7.5 g/L KCl 3 mol/L NH4Cl 0.1 mol/L


8. Literature

8.1. General references on ion selective electrodes

8.1.1 K. Cammann, Das Arbeiten mit ionenselektiven Elektroden. Springer Verlag, (1973)

8.1.2. Friedrich Oehme, Ionenselektive Elektroden, Hüthig Verlag, 2. Auflage

8.1.3 Jiri Koryta, Ion-selective electrodes, Cambrige University Press (1975)

8.1.4 Kirk-Othmer, ion selective electrodes, Band 13

8.1.5. Peter L.Bailey, Analysis with ion-selective-electrodes, 2. edition, Heyden, London

8.1.6. Römpp Chemielexikon, 9. Auflage, Band 3 2033-2034, Band 5 3811 und 3844 f

8.1.7. Analytischer Methoden-Führer, Orion Research 9. Ausgabe 1979

8.1.8. F. Weiske; Handling von ionenselektiven Elektroden, LaborPraxis Okt 93

8.2. References for fluoride determination with ion selective electrodes

General8.2.1. Anleitung zur ionenselektiven Fluorid-Elektrode. Ingold AG Urdorf

8.2.2. Hawkings R.C.; Dynamic Responce of the Fluoride Ion-Selective Electrode , AnalyticalChimica Acta, 102, 61-83, (1978)

8.2.3 Villa, A.E.; Rapid method for determination very low fluoride concentrations using anion-selective electrode. Analyst 113, 1299-1303, (1988)

Air / Exhaust

8.2.4. Elfter, L.A. and Decker, D.C.; Determination of Fluoride in Air and Stack Gas Samplesby use of an Ion Specific Electrode, Anal. Chem. 40(11),1658 (1968)

8.2.5. Buck, M. and Reusmann, G.; A New Semi-Automatic Method for Fluoride Determina-tion in Plant and Air Samples, Fluoride 4(1),5. (1971)

Waste water

8.2.6. Ciba, L.; Ion-Selective electrode determination of fluoride ions in products obtainedfrom industrial waste, Chem. Anal. (Warsaw) 38 (1) 129-131 (1993)

Drinking water

8.2.7. Harwood, J.E.; The use of an Ion-Selective Electrode for Routine Fluoride Analyses onWater Samples, Water Res. 3, 273 (1969)

8.2.8. Warner, T.B.; Determination of Fluoride Pollutants in Natural Waters Using a KnownAddition Technique, NRL Report 7216, Naval Resarch Laberatory, Washington, D.C.,December 24, (1969)

8.2.9 Schöller, F. and Kaspar, W.D.; The Fluorid Content of East Austrian Water and its De-termination by Means of a Specific Ion Electrode.

8.2.10. Gas/Wasser/Wärme/, 24(6), 115 (1970)


8.2.11. Warner, T.B. and Bressan, D.J.; Direct Measurment of less than 1 part per Billion Fluo-ride in Rain, Fog and Aerosols with Ion Selective Electrode. Anal.Chim. Acta 63(1),165 (1972).

8.2.12. ASTM D 1179-70

Milk

8.2.13. Konikoff, B.S.; The Bioavailability of Fluoride in Milk. La Dental J. 32/1, (1974)

8.2.14. Ericsson, Y., and Hellstrom, I.; Pilot Studies on the Fluoride Metabolism in Infants onDifferentFeedings. Acta Paediat. Scand. 61, 459 (1972)

Vitamins

8.2.15. Jones, B.C., Heveran, J.E. and Senkowski, B.Z.; Specific Ion Electrode Determinationof Fluoride in Multivitamin Preparations. J. Pharm. Sci. 58(5), 607 (1969)

Wine

8.2.16. Martin, C. and Brun, S.; Measurement of Fluoride in Wines. Trav. Soc. Pharm. Mont-pellier 29(3), 161 (1969)

8.2.17. De Baenst, G., Mertens, J., Van den Winkel, P. and Massart, D.L.; Potentiometric De-termination of Fluorid Ion in Wine. J. Pharm. belg. 28(2), 188 (1973)

Fish

8.2.18. Ke, P.E., Power, H.E. and Regier, L.W.; Flouride Content of Fish Protein Concentrateand RawFish. J. Sci. Food Ag. 21(2),108 (1970)

8.2.19 Wright, D.A., and Davison, A.W.; The Accumulation of Fluoride by Marine and Inter-tidal Animals. Environ. Pollut. 8, 1 (1975)

Vegetation

8.2.20 Galloway, H.L., Shoaf, R.E. and Skaggs, C.H.; A Rapid Method for the Determinationof Fluoride in Vegetation. Am. Ind. Hyg. Assoc. J. 721 (1975)

8.2.21 McQuaker, N.R. and Gurney, M.; Determination of Total Fluoride in Soil and Vegeta-tion Using Alkali Fusion - Selective Ion Electrode Technique. Anal. Chem. 49, 53(1977)

8.2.22 Villa, A.E.; Rapid Method for Determining Fluorid in Vegetation Using an Ion-Selec-tive Electrode. Analyst 104, 545 (1979)

8.2.23 Wang, C.Y.; Fluorine Ion Selective Electrode for Micro-Determination of Fluorine inOrganic Compounds. Microchem. J. 27, 455 (1982)

8.2.24 Wang C.Y.; Trace Analysis of Fluorine in Plants and Foods (Gran’sMethod). Fluoride22(3) 108-111 (1989)


Serum

8.2.25. Singer, L. and Amstrong, W.D.; Total Fluorid Content of Human Serum. Arch. OralBiol. 14, 1343 (1969)

8.2.26 Singer, L. and Amstrong, W.D.; Determination of Ionic (plus Ionizable) Fluoride in Bi-ological Fluids. Anal. Biochem. 42, 350 (1971)

Tooth care

8.2.27 Light, T.S. und Cappuccino, C.C.; Determination of Fluoride in Toothpaste using anIon Selective Electrode. Journal of Chemical Education Vol. 52 (4), 247 (1975)

Soil

8.2.28. McQuaker N.R. and Gurney, M.; Determination of Total Fluoride in Soil and Vegeta-tion using an Alkali Fusion-Selective Ion Electrode Technique.Anal. Chem. 49, 53 (1977)

8.2.29. Dracheva, L.N. and Stepanets, M.I.; Potentiometric determination of fluorid in soil.Gig.Sanit. (5-6) 65-67 (1992).

8.3. References for chloride determination with ion selective electrode

General8.3.1. Anleitung zur ionenselektiven Chlorid-Elektrode. Ingold AG Urdorf

8.3.2. Chapman B.R., Goldsmith I.R.; Determination of Chloride, Sodium and Potassium inSalted Foodstuffs using Ion-selective Electrodes and the Dry Sample Addition Method.Analyst 107, 1014-1018 (1982)

Water

8.3.3. Warner, T.B.; Ion Selective Electrodes in Seawater.Marine Technology Society 6th Annual Preprints, 2, 1495 (1970)

8.3.4. Ogata, N.; Dynamic Property of Chlorid Selective Electrode and ita Application to Sea-water. Jap. Analyst 21, 780 (1972)

8.3.5. Frost, J.G. An Indirect Potentiometric Determination of Chloride in Cleaning Solutionsfor Power Plant Boilers. Anal. Chim. Acta. 48, 321 (1969)

8.3.6. Marshall, G.B., Midgley, D.; Determination of Chloride in High-purity Waters in theRange 0-20 µg/L of Chloride Using Ion-selective Membran Electrodes IncorporatingMercury(I)Chloride. Analyst 104, 55-62 (1979)

8.3.7. Fischer, W.; Process of groundwater control regarding possible contaminations afterusing brckish water. Nachr. Mensch Umwelt 9(4),15-18 (1981)

8.3.8. Vieira, B.M.;Use of ion selective electrode in chloride determination in aqueous solu-tion to the 10-6 m level (0.1 ppm). Quim Nova 8 (3), 148-52 (1985)

8.3.9. Chloride in drinking water, waste water and salt soultions.Schweiz. Lab.Z. 43 (11), 431-2 (1986).


Dairy products

8.3.10 Muldoon, P.J. and Liska, B.J.; Chloride Ion Activity Electrode for the Detection of Ab-normal Milk. Dairy Sci. 54(1), 117 (1971)

8.3.11. Randell, A.W., Linklater, P.M.; The Rapid Analysis of Cheddar Cheese. The Determi-nation of Salt Content Using an Electrode Specific for Chloride.Australien J. Dairy Tech. 27(2), 51 (1972)

8.3.12 Liu, J., Neu, S., Zhang, H.; Use of ion-selective electrodes in determination of chloridesin milk. Shipin Kenxue (Beijing) 101, 49-50 (1988)

8.3.13 Turyan Y.I., Malyshev, A.M., Skhalyakho, A.Kh.; Potentiometric determination of so-dium chloride in water-insoluble samples using a chlorid-selective electrode.Zh.Anal.Khim 47(7), 1334-7 (1992)

Foods

8.3.14. Moody, G.J., Thomas, J.D.R.; The Determination of Chloride in Vegetables Fruits andJuices with Ion-Selective Electrode. Food Tech 12, 193 (1977)

8.3.15 Sucman, E., Zima, St., Rochova, I.; Determination of the content of chloride ion in sala-mi with chloride selective electrode.Sb UVTIZ, Potravin Vedy 3(2), 95-101 (1985)

8.3.16 Dracheva, L.V., Radchenko, A.F.; Determination of chlorid ions in food products usingchloride selective electrode. Zavod Lab 57(1), 14-15 (1991)

Plants

8.3.17. Rosol, M.,Supuka, J.; Evaluation of the use of an ion selective electrode for chloridedetermination in plants. Biologia (Bratislava) 39 (1), 41-48 (1984).

Special

8.3.18 Leser, K.H., Sigrist, G.V.; Application of chloride selective microelectrode to renal testdyes and other food or cosmetic dyes.Pfluegers Arch. 406(1),88-90 (1986)


8.4. References for nitrate determination with ion selective electrode

General8.4.1. Anleitung zur ionenselektiven Nitrat-Elektrode. Ingold AG Urdorf

8.4.2. Milham,P.J., Awad,A.S., Paull, R.E.; Analysis of Plants, Soils and Waters for Nitrate byusing an Ion-Selective Electrode.Analyst, 95 (1133),751 (1970)

Water8.4.3. Shaw, E.C. and Wiley, P.; Nitrate Ion Concentration in Well Water.

Calif. Agr., 5, 11 (1969)

8.4.4. Sommerfeldt, T.G., Milne, R.A.; Use of Nitrate-Specific Ion Electrode for the Determi-nation of Nitrate Nitrogen in Surface and Ground Water.Soil.Sic.Plant.Anal. 2 (6), 415 (1971)

8.4.5. Flasarova M., Novak, J.; Determination of nitrites in mixture with nitrates by using anitrate selective electrode. Chem Listy, Vol 80 (3) 328-31 (1986)(Determination in soil and wastewater)

8.4.6. Huang, C., Yang, L.; Consecutive determination of nitrate, nitrite and ammonium inrainwater with a nitrate electrode.Fenxi Shiyanshi, 9 (5), 34-35 (1990)

Vegetables8.4.7. Bestimmung von Nitrat in Frischgemüse. Flugschrift Nr 106, 3 Auflage 1990, Eidgenös-

sische Forschungsanstalt für Obst-, Wein- und Gartenbau, Wädenswil

8.4.8. Kolbe, H. und Müller, K.; Vergleichende Untersuchung über semiquantitative undquantitative Methoden zur Bestimmung von Nitrat in Kartoffeln. Institut für Agrikul-turchemie der Georg-August Universität Göttingen

8.4.9. Kniel, B., Rauh, J. und Gnoth, K.; Potentiometrische Nitratbestimmung in Rote-Bete-Säfte als routienemässig anwendbare Methode für die Qualitäts-sicherung.

8.4.10. Paul, J.L. and Carlson, R.M.; Nitrat Determination in Plant Extracts by the Nitrat Elek-trode. J. Agr. Food Chem., 16(5), 766 (1968)

8.4.11. Barker, A.V., Peck, N.H. and MacDonald, G.E.; Nitrate Accumulation in Vegetables.Spinach Grown in Upland Soils. Argron.J. 63(1), 126 (1971)

8.4.12. McCaslin, B.D., Franklin, W.T. and Dillon, M.A.; Rapid Determination of Nitrate Ni-trogen in Sugarbeets with the Specific Ion Electrode. Journal .of the A.S.S.B.T. 16 (1),64 (1970)

8.4.13. Henscheid, T., Schoenrock, K. and Berger, P.; Application of Ion-Selective Electrodesin the Beet Sugar Industry.Journal .of the A.S.S.B.T., 16(6), 482 (1971)

8.4.14. Kolbe, H., Müller, K.; Vergleichende Untersuchungen über semiquatitative und quanti-tative Methoden zur Bestimmung von Nitrat in Kartoffeln.Potato Resarch 29, 333 - 346 (1989)

8.4.15. Mitrakas, M.G.; Nitrate determination in sugar beet sap extracted with lead acetateleadmonoxide using an ion-selective electrode.Commun Soil Sci Plant Anal. 22 (5-6), 589-96 (1991)


Meat8.4.16. .Zhou, X., Zhang, T.; Determination of nitrate and nitrite in meat products with the ni-

trate selective electrode. Wuxi Qinggongye; Xueyuan Xuebao, Vol 10(2) 19-29 (1991)ISSN:1001-7453

Fruits8.4.17. Kotova, L.V., Selezneva G.P.; Method for determination of nitrates in apples by a nitrate-

selective electrode. Biokhim Methody Analiza Plodov, Kishinev 90

Soils8.4.18. Simeonov,V.; Rapid Determination of Nitrate Nitrogen in Soils. Talanta, 24, 199 (1977)

8.5. References for sodium and potassium determinations with ion selective elec-trodes

General

8.5.1. Anleitung zur ionenselektiven Kalium-Elektrode. Ingold AG Urdorf

8.5.2. Anleitung zur ionenselektiven Natrium-Elektrode. Ingold AG Urdorf

8.5.3. Schindler, J.G.; Natrium selektive Monensin-PVC-Membranelektrode mit Festableitung.Fresenius Z.Anal. Chem., 320, 258-260 (1985)

8.5.4. Srivastava, S.K.; Determination of Sodium by Ion-selective Potentiometry.ANALYST, 109, 667 (1984)

Water

8.5.5. Chiu,Y.P., Juang, S.F.; The micellar dissociation concentration of bile salts in water witha sodium ion electrode. Chim. Oggi, 9, (3), 55-59 (1991)

Foods

8.5.6. McNerney, F.G.; Collaborative Study of the Determination of Sodium in Dietetic Foodsby the Sodium Ion Electrode Method. JAOAC., 59 (5), 1131 (1976)

8.5.7. Kindstedt, P.S., Mattick, L.R.; Simple selective sodium ion electrode measure of sodiumin cheese. J.Dairy Sci., 66(5), 988-93 (1983)

8.5.8. Kindstedt, P.S., Kosikowski, F.V.; Measurement of sodiumchloride in cheese by simplesodium ion electrode method. J.Dairy Sci., 67(4), 879-83 (1984)

Blood

8.5.9. Reichenbach, K.; Influences of proteins and blood cells on the results of direct potentio-metric measurements in blood - demonstrated on sodium determination with glass elec-trode. Bioelectroanal, 1.Symp., Akad Kiado, Budapest, p. 341-51 (1987)

8.5.10. Annan, W., Kirwan, N.A., Robertson W.S.; An evaluation of the NOVA 1 ion selectiveanalyser for sodium and potassium determination. J.Autom Chem Vol 2(4) 212-20(1980)


Soil

8.5.11. Puffer, J.H., Cohen, R.S.; Field Determination of Sodium and Potassium in Feldsparsby Ion-Selective Electrodes.Chem. Geol., 15, 217 (1975)

Glass

8.5.12. Knupp, R.C.; Use of Ion-Selective Electrodes for Analysis of Sodium and Calcium inGlass Batch.Chem. Geol., 15, 217 (1977)

Internet:

Titration homepage of METTLER TOLEDO:http://www.titration.netCheck also the application database at this Internet address.


9. Sample index

Apple juice 42, 50Aquarium water 32Baby food 20Beans (canned) 20Bouillon 50Cabbage 32, 33Cabbage, white 35Carrot juice 20, 32, 42Carrots 32, 33Cheese 20Cucumbers 32Drinking water 10, 13, 32, 50Elderberry juice 42Fertilizer solution 42Fluoride tablets 10Garden soil 42Grape juice 42, 50Herb paté 50Iceberg lettuce, head 32Infusion solution 42, 50Lettuce head 32, 33Mayonnaise 20Milk 10, 20, 42, 50Mineral water 10, 50Mouthwash 10Orange juice 42Peas (canned) 20, 22Potatoes 32Red beet juice 32, 42Red beets 35River water 13Salad dressing 20Silver beet 32Snow 10Soil 42Spinach 32, 35Spring water 13Table salt 10Tomato juice 20Tomato ketchup 20Toothpaste 10Wine 10, 42, 48


Notes


This applications brochure represents selected, possible application examples. These have been tested with all possiblecare in our lab with the analytical instruments mentioned in the bulletin. The experiments were conducted and theresulting data evaluated based on our current state of knowledge.

However, the applications brochure does not absolve you from personally testing its suitability for your intended meth-ods, instruments and purposes. As the use and transfer of an application example are beyond our control, we cannotaccept any responsibility for the use or consequences of the applications contained in this brochure.

When chemicals and solvents are used, the general safety rules and the directions of the producer must beobserved.

Mettler-Toledo GmbHAnalyticalCH-8603 Schwerzenbach, SchweizTelefon (01) 806 77 11, Fax (01) 806 73 50Internet: http://www.mt.com

Subject to technical changes© 07/04 Mettler-Toledo GmbH, ME-51724646Printed in Switzerland on 100% chlorine-freepaper, for the sake of our environment.

For all other countries:Mettler-Toledo GmbHPO Box, VI-400, CH-8606 Greifensee, SchweizTel. (01) 944 22 11, Fax (01) 944 31 70

AT Mettler-Toledo GmbH., A-1100 WienTel. +43-1-604 19 80, Fax +43-1-604 28 80

AU Mettler-Toledo Ltd., Port Melbourne, Victoria 3207Tel. +61-3-9644 5700, Fax +61-3-9645 3935

BE N.V. Mettler-Toledo S.A., B-1932 ZaventemTel. +32-2-334 02 11, Fax +32-2-334 03 34

CH Mettler-Toledo (Schweiz) AG, CH-8606 GreifenseeTel. +41-1-944 45 45, Fax +41-1-944 45 10

CN Mettler-Toledo (Shanghai) Ltd., Shanghai 200233Tel. +86-21-6485 0435, Fax +86-21-6485 3351

CZ Mettler-Toledo, spol, s.r.o., CZ-12000 Praha 2Tel. +420-2-25 49 62, Fax +420-2-2424 7583

DE Mettler-Toledo GmbH, D-35353 GiessenTel. +49-6-41 50 70, Fax +49-6-41 507 128

DK Mettler-Toledo A/S, DK-2600 GlostrupTel. +45-4327 0800, Fax +45-4327 0828

ES Mettler-Toledo S.A.E., E-08038 BarcelonaTel. +34-3-223 22 22, Fax +34-3-223 02 71

FR Mettler-Toledo s.a., F-78222 ViroflayTel. +33-1-3097 1717, Fax +33-1-3097 1616

HK Mettler-Toledo (HK) Ltd., KowloonTel. +852-2744 1221, Fax +852-2744 6878

HR Mettler-Toledo, d.o.o., HR-10000 ZagrebTel. +385-1-230 41 47, Fax +385-1-233 63 17

HU Mettler-Toledo, KFT, H-1139 BudapestTel. +36-1-288 40 40, Fax +36-1-288 40 50

IT Mettler-Toledo S.p.A., I-20026 Novate MilaneseTel. +39-2-333 321, Fax +39-2-356 29 73

JP Mettler-Toledo K.K., Tokyo 143-0006Tel. +81-3-5762-0606, Fax +81-3-5762-0756

KR Mettler-Toledo (Korea) Ltd., Seoul (135-090)Tel. +82-2-518 20 04, Fax +82-2-518 08 13

KZ Mettler-Toledo CA, 480009 AlmatyTel. +7- 3272-608 834, Fax +7-3272-608 835

MY Mettler-Toledo (M) Sdn. Bhd. 47301 Petaling JayaTel. +60-3-703 27 73, Fax +60-3-703 17 72

MY Mettler-Toledo (S.E.A.), 47301 Petaling JayaTel. +60-3-704 17 73, Fax +60-3-703 17 72

MX Mettler-Toledo S.A. de C.V., México C.P. 06430Tel. +52-5-547 57 00, Fax +52-5-541 22 28

NL Mettler-Toledo B.V., NL-4000 HA TielTel. +31-3-4463 8363, Fax +31-3-4463 8390

PL Mettler-Toledo, Sp. z o.o., PL-02-929 WarszawaTel. +48-22-651 92 32, Fax +48-22-651 71 72

RU Mettler-Toledo C.I.S. AG, 10 1000 MoscowTel. +7-095-921 92 11, Fax +7-095-921 63 53

SE Mettler-Toledo AB, S-12008 StockholmTel. +46-8-702 50 00, Fax +46-8-642 45 62

SG Mettler-Toledo (S) Pte. Ltd., Singapore 139944Tel. +65-7786 779, Fax +65-7786 639

SK Mettler-Toledo, SK-82104 BratislavaTel. +421-7-4342 7496, Fax +421-7-4333 7190

SI Mettler-Toledo, d.o.o., SI-1236 TrzinTel. +386-61-162 18 01, Fax +386-61-162 17 89

TH Mettler-Toledo (Thailand) Ltd., Bangkok 10310Tel. +66-2-719 64 80, Fax +66-2-719 64 79

TW Mettler-Toledo Pac Rim AG, TaipeiTel. +886-2-2579 5955, Fax +886-2-2579 5977

UK Mettler-Toledo Ltd., Leicester, LE4 1AWTel. +44-116-235 70 70, Fax +44-116-236 63 99

US Mettler-Toledo, Inc., Columbus, OH 43240Tel. +1-614-438 4511, Fax +1-614-438 4900

METTLER TOLEDO on the WWW

You can also reach us on the World Wide Web. There youwill find information on other products and services ofMETTLER TOLEDO and interesting information about ourcompany.The address is http://www.mt.com

direct measurement with ion selective electrodesbikeitech.com/datas/es_free3/f_4979110fc3bc9.pdf ·...

Documents