TraceSELECT®– High Purity Reagents for...

■ Sample Preparation

■ Analysis

■ Calibration

Inorganic Trace Analysis

2 sigma-aldrich.com/traceselect sigma-aldrich.com/techservice

• Produced and certified in double accredited laboratory according to ISO/IEC 17025 and ISO Guide 34

• Unique level of accuracy & lot specific certified values incl. uncertainty

• Traceable to at least two independent references (i.e. NIST, BAM or SI unit kg)

• Highly sophisticated packaging & documentation with expiry date

• ICP standards list up to 70 trace impurities

TraceCERT®

Swiss Precision Meets Analytical Competence

Ordering InformationFind our actual list of TraceCERT reference materials for calibration and method validation at http://www.sigma-aldrich.com/tracecertFor custom standards please contact us at: CustomStandards@sial.com

Traceable Certified Reference Materials for ICP, AAS and IC

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Inorganic Trace AnalysisTable of Contents

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

Sample Preparation for Trace Analysis: TraceSELECTUltra and TraceSELECT ........................................................ 6

Trace Analysis: High Purity Reagents ........................................................................................................................ 8

Matrix Modifiers .................................................................................................................................................... 8

Spectroscopic Buffers for Flame AAS ..................................................................................................................... 8

Reducing Agents for Hydride AAS ......................................................................................................................... 8

Solvents for Trace Metal Speciation Analysis .......................................................................................................... 9

Certified Eluent Concentrates and High Purity Water for Ion Chromatography ..................................................... 10

Ultra Pure Reagents for Voltammetry ................................................................................................................... 10

Calibration for Trace Analysis: TraceCERT - Certified Reference Materials ..........................................................11

Fluka-brand TraceSELECT and TraceSELECTUltra reagents from Sigma-Aldrich include high purity acids, bases and salts designed for trace and ultra-trace analysis.

For a complete list of products, visit our website:

sigma-aldrich.com/traceselect

• Produced and certified in double accredited laboratory according to ISO/IEC 17025 and ISO Guide 34

• Unique level of accuracy & lot specific certified values incl. uncertainty

• Traceable to at least two independent references (i.e. NIST, BAM or SI unit kg)

• Highly sophisticated packaging & documentation with expiry date

• ICP standards list up to 70 trace impurities

TraceCERT®

Swiss Precision Meets Analytical Competence

Ordering InformationFind our actual list of TraceCERT reference materials for calibration and method validation at http://www.sigma-aldrich.com/tracecertFor custom standards please contact us at: CustomStandards@sial.com

Traceable Certified Reference Materials for ICP, AAS and IC

4 sigma-aldrich.com/traceselect sigma-aldrich.com/techservice

IntroductionAs a supplier of analytical reagents

and standards, quality assurance is of

prime importance to Fluka. We

employ a comprehensive Quality

Assurance System according to EN

29001 (ISO 9001). Each of our more

than 20,000 products is manufac-

tured to clear, guaranteed specifications. The large variety

of modern analytical methods (e.g., ICP-OES, ICP-MS,

flame AAS, graphite furnace AAS) allows for specifically

tailored control and analysis procedures for each product.

Reagents for Inorganic Trace Analysis

Sensitive trace analysis applications require extremely

pure sample preparation reagents. These digestive

reagents cannot contain metal ions or other impurities.

Further, complete decomposition of the sample is required

to achieve reproducible and accurate elemental results by

instrumental analytical methods.

Sample wet digestion/dissolution is a method that

breaks down the components of a matrix into simple

chemical forms. This digestion can occur with the

introduction of energy, such as heat; by using a chemical

reagent, such as an acid; or by a combination of the two

methods. Most analytical measurements using highly

sensitive methods (AAS, ICP-AES, stripping voltammetry,

ion chromatography, etc.) are performed on samples in

solution. One of the most effective and economical

sample preparation methods is microwave digestion. In

most cases, achieving homogeneity and mineralization of

the sample is sufficient.

UV photolysis using hydrogen peroxide and either

potassium persulfate or nitric acid is very often the

method of choice for the decomposition of organic

impurities in aqueous solutions.

The most commonly used reagents for wet decomposi-

tion are mineral and oxidizing acids. Wet decomposition

has the advantage of being effective on both inorganic

and organic materials. It often destroys or removes the

sample matrix, thus helping to reduce or eliminate some

types of interference. Table 1 provides an annotated

overview of the acids used for wet digestion.

Table 1. Digestion/Dissolution Acids and Bases

HNO3

Nitric acid is the most frequently utilized sample dissolu-

tion medium. It oxidizes metals not dissolved by HCl and

other non-oxidizing acids. Au, Pt metals (expect Pd), Nb,

Ta, and Zr are not dissolved. Al and Cr are passivated. Sn,

Sb, and W give insoluble hydrous oxides. Dissolves most

sulfides (except HgS). Unfortunately, the carbon con-

tained in organic materials is only partly converted to CO2

by HNO3 at temperatures up to 200 °C. Nitric acid should

never be used for the digestion of highly aromatic

compounds because of the potential for the formation of

highly explosive compounds. In the case of alcohols, the

samples should be pretreated with sulfuric acid.

HClHydrochloric acid is used for many salts of weak acids,

e.g., carbonates, phosphates, some oxides, and some

sulfides.

H2SO4 Sulfuric acid is used when its high boiling point (300 °C)

is an advantage, as in expelling a volatile product or

increasing the reaction rate. It provides dehydrating and

oxidizing properties at high temperatures.

HClO4 Perchloric acid is a very powerful oxidizing agent at

fuming temperatures (boiling point 203 °C). It is usually

mixed with HNO3 to oxidize easily attacked organic

matter that might otherwise react violently with HClO4.

H2SO4 (dehydrating agent) increases oxidizing power.

Good solvent for stainless steel and for sulfides.

HF Hydrofluoric acid is used for digestion of silacaceous

samples and as an auxiliary reagent to HNO3 or HClO4 to

eliminate fluoride. With HNO3, HF dissolves Ti, W, Nb,

and Zr (and their carbides, nitrides, and borides) as a

result of formation of complex fluorides. Certain refrac-

tory silicates and other minerals are not decomposed;

these must be dissolved by fusion.

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H2O2 Hydrogen peroxide is a very popular oxidizing reagent

as it is converted to water and oxygen during the

oxidation of biological material. Additional advantages

are that there is no acid corrosion of the digestion

vessel PTFE walls, no formation of insoluble salts with

an acid anion, and no change of the sample matrix by

an acid. Because of its strong oxidation power, only

small amounts of H2O2 need be used so concentrated

sample solutions can be obtained.

AcOH Acetic acid is most often used for the extraction of

metallic impurities together with sodium acetate.

HBrHydrobromic acid is a non-oxidizing acid. It is used in

some special applications because it yields better

reductive selectivity in the determination of Se(VI) by

Hydride Generation-Laser Induced Fluorescence

(HG-LIF) than HCl.

H3PO4 Phosphoric acid is commonly used in the semiconductor

industry to both clean and etch metal surfaces. The

concentration of the phosphoric acid is critical to

optimizing these processes.

H2O Water ensures the highest accuracy in trace analysis of

ppt range by minimizing blank values.

TMAH Tetramethylammonium hydroxide [(CH3)4NOH] is an

efficient strong alkali used for solubilizing soft tissues

and food stuffs. Compared to conventional alkaline

sample digestion procedures using NaOH or KOH, using

TMAH enables more accurate analysis due to its lower

matrix effect. A diluted 0.3 M TMAH solution is also

used during the lithographic process in the semicon-

ductor industry.

NaOHSodium hydroxide is frequently used for melting

digestions at 500 °C. It attacks platinum and porcelain.

Residue is dissolved with 12 M hydrochloric acid.

Please see our entire selection of high purity digestion reagents at sigma-aldrich.com/traceselect

1. Feng, X.; Wu, S.; Wharmby, A.; Wittmeier, A. Microwave digestion of plant and grain standard reference materials in nitric and hydrofluoric acids for multi-elemental de-termination by inductively coupled plasma mass spectrometry. J. Anal. At. Spectrom. 1999, 14, 939–946.

2. Golimowski J.; Golimowska, K. UV photooxidation as pretreatment step in inorganic analysis of environmental samples. Anal. Chim. Acta. 1996, 325, 111–133.

3. Vandecasteele, C.; Block, C. B. Modern Methods for Trace Element Determination; Wiley: Chichester, UK, 1997; pp 1–8.

4. Sampling and Sample Preparation; Stoeppler, M., Ed; Springer: Berlin, 1997.

5. Sah, R. N.; Miller, R. O. Spontaneous reaction for acid dissolution of biological tissues in closed vessels. Anal. Chem. 1992, 64, 230.

6. Inductively coupled plasmas in analytical atomic spectrometry; Montaser, A.; Go-lightly, D. W., Eds.; VCH: New York, 1992; pp 473–516.

7. Tracy, M. L.; Moeller, G. Continuous flow vapor generation for inductively coupled argon plasma spectrometric analysis; Part 1: Selenium. J. Assoc. Off. Anal. Chem. 1990, 73, 404–410.

8. Pacquette, H. L.; Elwood, S. A.; Ezer, M.; Simeonsson, J. B. A comparison of continu-ous flow hydride generation laser-induced fluorescence and laser-enhanced ioniza-tion spectrometry approaches for parts per trillion level measurements of arsenic, selenium and antimony. J. Anal. At. Spectrom. 2001, 16, 152–158.

9. Sun, Y. C.; et al. Combining electrothermal vaporization inductively coupled plasma mass spectrometry with in situ TMAH thermochemolysis for the direct determination of trace impurities in a polymer-based photoresist. J. Anal. At. Spectrom. 2006, 21, 311–316.

10. Jeitziner, M. High-purity TMAH for alkaline digestion of biological samples. Analytix 2008, 1, 17.

KOH Potassium hydroxide is frequently used for melting digestions

at 500 °C. It attacks platinum and porcelain. Residue is

dissolved with 12 M hydrochloric acid.

K2CO3 Potassium carbonate is the classic reagent for melting diges -

tions at 800 °C. Residue is dissolved with hydrochloric acid.

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Sample Preparation for Trace Analysis: TraceSELECTUltra and TraceSELECTUltra-pure acids, bases, and salts for smelting and wet digestion in environmental, water, and food analysis

Sample preparation for trace

analysis requires reagents of the

highest purity. Our TraceSELECTUltra

products for ultra-trace analysis at ppb

and even ppt levels are produced by

sub-boiling distillation. Sub-boiling is

recognized as the best way to obtain

high purity acids with the lowest blank

values for ultra-trace analysis. The

technique is based on the evaporation

of liquid by infrared heating at the

surface. It avoids violent boiling and

the formation of liquid aerosols that

can be transported with the distillate.

To maintain their high purity,

TraceSELECTUltra products are

supplied in PTFE PFA (fluoropolymer)

bottles. Water and ortho-phosphoric

acid are supplied in specially pre-

leached HDPE bottles. Recent process

improvements have allowed us to

reduce our impurity specifications in

order to guarantee the lowest levels of

trace impurities in our TraceSELECTUl-

tra products.

For more information, see our Web

site: sigma-aldrich.com/traceselect

Table 2. TraceSELECTUltra reagents

Cat. No. Brand Product Name Specification Pack Sizes

07692 Fluka Acetic acid 99.0 % (T) 250 mL, 1 L

16748 Fluka Ammonium hydroxide solution 25 % (T) 250 mL, 1 L

23828 Fluka Hydrobromic acid 44 % (T) 250 mL, 1 L

96208 Fluka Hydrochloric acid 30 % (T) 250 mL, 1 L

02658 Fluka Hydrofluoric acid 49 % (acidimetric) 250 mL, 1 L

16911 Fluka Hydrogen peroxide solution 30 % (RT) 250 mL, 1 L, 5 L

02650 Fluka Nitric acid ~ 65 % (T) 250 mL, 1 L

12415 Fluka Perchloric acid 67-72 % (T) 250 mL, 1 L

64957 Fluka Phosphoric acid 85 % (T) 250 mL, 1 L

77239 Fluka Sulfuric acid 95 % (T) 250 mL, 1 L

14211 Fluka Water 1 L

1. Mitchell, J. W. Purification of Analytical Reagents. Talanta, 1982, 29, 993–1002.

The acids, bases, and salts in

the TraceSELECT series have

been developed for sample

preparation and analysis in the

ppb (μg/kg) trace range. Purity

and composition are guaran-

teed with our careful prepara-

tion, testing, and verification of

the final product for metal

content and ionic trace

impurities using ICP-OES, ICP-MS and ion chromatography. To further guaran-

tee purity and stability, TraceSELECT products are packaged in high-quality

containers appropriate for the particular product.

The Sigma-Aldrich Quality Management System guarantees consistent

quality and safety for all TraceSELECTUltra and TraceSELECT products. The

reagents are produced and bottled under clean-room conditions and are

delivered with a Certificate of Analysis.

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Table 3. TraceSELECT reagents

Cat. No. Brand Product Name Specification Pack Sizes

45727 Fluka Acetic acid ≥ 99.0% (T) 100 mL, 500 mL

09857 Fluka Ammonium hydroxide solution ≥ 25% in water 100 mL, 500 mL

06454 Fluka Formic acid ≥ 88.0% 250 mL

08256 Fluka Hydrochloric acid ≥ 30% 100 mL, 500 mL

84415 Fluka Hydrochloric acid ≥ 37% fuming (T) 100 mL, 500 mL

47559 Fluka Hydrofluoric acid 47-51% (AT) 100 mL, 500 mL

95321 Fluka Hydrogen peroxide solution ≥ 30% (RT) 100 mL, 500 mL

84385 Fluka Nitric acid > 69.5% (T) 250 mL, 500 mL

77227 Fluka Perchloric acid 67-71% (T) 100 mL, 500 mL, 1 L

79614 Fluka Phosphoric acid ≥ 85% (T) 100 mL, 500 mL

18498 Fluka Phosphorus oxychloride ≥99.9999% 250 mL

30955 Fluka Potassium hydroxide solution ≥ 30% in water (T) 250 mL

13171 Fluka Sodium hydroxide solution ≥ 30% in water (T) 250 mL

84716 Fluka Sulfuric acid ≥ 95% (T) 500 mL

68556 Fluka Tetramethylammonium 25% in H2O 250 mL hydroxide solution

95305 Fluka Water 500 mL, 1 L, 2.5 L, 10 L

Melting digestion is used for solid samples like ores, rock, metals, alloys, ceramic, and

cement, in order to obtain a homogenous residue, which can be dissolved in diluted

TraceSELECT acids. Our TraceSELECT salts obtain a very high purity, with metal traces

typically below 10 μg/kg (10 ppb).

Table 4. TraceSELECT salts

Cat. No. Brand Product Name Specification Pack Sizes

73432 Fluka Ammonium acetate ≥ 99.9999% 100 g

09725 Fluka Ammonium chloride ≥ 99.9995% 25 g, 100 g

09726 Fluka Ammonium phosphate monobasic ≥ 99.9999% 25 g, 100 g

09979 Fluka Ammonium sulfate ≥ 99.9999% 100 g

40581 Fluka Cesium bromide ≥ 99.999% 25 g

90033 Fluka Cesium chloride ≥ 99.9995% 25 g, 100 g

62462 Fluka Lithium carbonate ≥ 99.995% 25 g, 100 g

60348 Fluka Potassium bisulfate ≥ 99.999% 25 g

60111 Fluka Potassium carbonate sesquihydrate ≥ 99.995% 50 g

05257 Fluka Potassium chloride ≥ 99.9995% 25 g, 100 g

60216 Fluka Potassium phosphate monobasic ≥ 99.995% 25 g, 100 g

60371 Fluka Potassium hydroxide hydrate ≥ 99.995% 25 g

60429 Fluka Potassium nitrate ≥ 99.995% 25 g, 100 g

60347 Fluka Potassium phosphate dibasic ≥ 99.999% 100 g

59929 Fluka Sodium acetate ≥ 99.999% 25 g, 100 g

01963 Fluka Sodium bromide ≥ 99.995% 25 g

71347 Fluka Sodium carbonate ≥ 99.9999% 25 g, 100 g

38979 Fluka Sodium chloride ≥ 99.999% 25 g, 100 g

01968 Fluka Sodium hydroxide monohydrate ≥ 99.9995% 25 g, 100 g

71752 Fluka Sodium nitrate ≥ 99.999% 25 g, 100 g

71629 Fluka Sodium phosphate dibasic ≥ 99.999% 100 g

71492 Fluka Sodium phosphate monobasic ≥ 99.999% 25 g, 100 g

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Reducing Agents for Hydride AAS

In graphite furnace AAS,

element determinations are more

and more often being carried out

with matrix modifiers. Chemical

modification should be considered

if an analyte is highly volatile, or if

the analyte and matrix volatilize at

similar temperatures. Such

modification would allow ashing

at higher (or atomization at lower)

furnace temperatures, resulting in

elimination of the matrix with no

loss of the analyte (or atomization

of the analyte, but not the

matrix). Depending on the

element to be determined, various

substances are used; however,

Trace Analysis: High Purity Reagents Matrix Modifiers

Spectroscopic Buffers for Flame AAS

Table 6. Spectroscopic Buffers for Flame AAS

Cat. No. Brand Product Name Specification Pack Sizes

20980 Fluka Aluminum nitrate cesium Buffer Solution according 500 mL chloride buffer for flame to Schuhknecht and atomic absorption spectrometry Schinkel

20982 Fluka Cesium chloride Lanthanum Buffer solution according 500 mL chloride buffer for flame to Schinkel atomic absorption spectrometry

95164 Fluka Cesium chloride Lanthanum CsCl 100 g/L, LaCl3 250 mL chloride buffer for flame 100 g/L (in water) atomic absorption spectrometry

Table 7. Reducing Agents for Hydride AAS

Cat. No. Brand Product Name Specification Pack Sizes

55459 Fluka Hydroxylamine hydrochloride puriss. p.a., ≥99.0% 50 g, 250 g for AAS

71321 Fluka Sodium borohydride puriss. p.a., ≥96.0% 25 g, 100 g for the determination of hydride formers by AAS

96527 Fluka Tin(II) chloride dihydrate purum p.a., ≥96.0%, 50 g, 250 g Hg ≤0.01 mg/kg

Table 5. Matrix Modifiers

Cat. No. Brand Product Name Specification Pack Sizes

428922 Aldrich Ammonium hydrogenphosphate ~40% (w/v) in H2O 100 mL matrix modifier

428868 Aldrich Calcium matrix modifier 2% Ca in 1 wt. % HNO3 100 mL

95164 Fluka Cesium chloride/Lanthanum CsCl and LaCl3 250 mL chloride matrix modifier 100 g/L each

428884 Aldrich Lanthanum matrix 5% La in 1 wt. % HCl 100 mL modifier solution

63043 Fluka Magnesium matrix modifier puriss. p.a., 10.0 g/L Mg 50 mL in ~17 wt.% HNO3

428906 Aldrich Nickel matrix modifier 5% Ni in 1 wt. % HNO3 100 mL

76040 Fluka Palladium matrix modifier puriss. p.a., 10.0 g/L Pd 50 mL in ~15 wt.% HNO3

palladium nitrate has become one of the most popular. A primary criterion for

such substances is the absence of the element to be analyzed. For this reason, the

recommended reagents indicated below have been specially tested for their

suitability as matrix modifiers.

In flame AAS, spectroscopic

buffers are often used to suppress

physical, ionization, and chemical

interferences. The Schuhknecht

and Schinkel buffer solution, as

used in the determination of alkali

elements, has become particularly

important. A multi-element

standard for the elements lithium,

sodium, and potassium is also

available for this method. The

Schinkel buffer solution enables

the method to be expanded to include up to 14 mono- and divalent elements,

with simple calibration being all that is required for the analysis.

Hydride AAS is used for the

analysis (especially traces) of

arsenic, antimony, tin, selenium,

bismuth, and mercury. It is used

to separate and preconcentrate

analytes from sample matrices by

a reaction that turns them into

their hydride vapors. Sodium

borohydride is the common

reagent of choice for the

reduction. Fluka reagents are specifically analyzed to ensure the absence of

hydride-generating metals.

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Solvents for Trace Metal Speciation Analysis

...TraceSELECT solvents for LC-ICP-MS applications

Table 8 TraceSELECT Solvents Ideal for Speciation Analysis

Cat. No. Brand Product Name Specification Pack sizes

01324 Fluka Acetonitrile TraceSELECT (≥99.9%) 1 L

42105 Fluka Methanol TraceSELECT (≥99.9%) 1 L

14211 Fluka Water TraceSELECTUltra 1 L

1. Michalke, B. The coupling of LC to ICP-MS in element speciation; Part II: Recent trends in application. Trends in Analyti-cal Chemistry, 2002, 21(3), 154–165.

2. IUPAC, Pure and Applied Chemistry, 2000, 72, 1453–1470.

The toxicity of trace metals in

food, clinical chemistry, biology,

and environmental sciences is an

area of increasing interest. In the

environment, many diverse

species of an element can be

present, and different species of

the same element can possess

very different degrees of toxicity.

Monitoring elemental species

requires an analytical method that

is sensitive and specific enough to

resolve and quantify the individual

species at ultra-trace levels, as an

individual toxic species may consti-

tute only a fraction of an ele-

ment’s total concentration in a

sample. The coupling of the two

well-established analytical

techniques, HPLC and inductively

coupled plasma-mass spectrom-

etry (ICP-MS), is straightforward

primarily because the flow rates

commonly used with LC are

compatible to conventional liquid

sample introduction systems, such

as those based on pneumatic

nebulization. Thus, the outlet of

the LC column is directly con-

nected to the ICP-MS nebulizer.

This technique is especially useful

in carrying out automated

high-throughput speciation

analysis. International trends show

speciation of metals as an area of

very high research interest. In the

future, speciation of biological

samples will undoubtedly involve

determinations of which organic

molecules attract which metals in

specific sample types.

ICP-MS is a superior

detection technique for trace

elements in general, but

especially for elements of

interest such as arsenic, selenium, cadmium, iodine, and others in chromato-

graphic eluents.

Sigma-Aldrich has recently developed new high purity TraceSELECT solvents for

speciation analysis by LC-ICP-MS. TraceSELECT solvents undergo rigorous

purification procedures followed by UV spectroscopy, IC, and ICP-MS testing to

assure high chemical purity and high UV transmittance. The blank values for

metal traces in these solvents are in the ppb range or lower.

Definition of speciation analysis

The International Union of Pure and Applied Chemistry (IUPAC) defines

speciation analysis as the “analytical activities of identifying and/or measuring the

quantities of one or more individual chemical species in a sample.” A chemical

species is a “specific form of an element defined as to isotopic composition,

electronic or oxidation state, and/or complex or molecular structure.”

In speciation analysis, the objective is usually to determine the identity and/or

concentration of one or more chemical species in a sample, often of natural origin

and therefore potentially containing many different species. Care must be taken

to choose and execute the analysis to maximize sensitivity and specificity.

Performing a speciation analysis in a complex mixture involves separation,

identification, and characterization of various forms of elements in the sample.

The most commonly used strategy for speciation analysis is to perform a separa-

tion step before a generic detector.

LC separation coupled with ICP-MS

The hyphenated technique HPLC-ICP-MS is a robust, sensitive element-selective

method capable of giving a complete picture of the elemental species in a

solution. The elemental response is usually independent of species, so it is often

possible to quantify a species even when its structure is unknown (assuming good

HPLC recovery). Identification, however, is based solely on retention time

matching; hence, a compound in the sample can be identified only by comparison

with a standard.

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8Min

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Certified Eluent Concentrates and High Purity Water for Ion Chromatography

Table 9. Certified Eluent Concentrates and High Purity Water for Ion Chromatography from Sigma-Aldrich

Cat. No. Brand Product Name Specification Pack Sizes1

50972 Fluka 2,6-Pyridinedicarboxylic for IC, 0.02 M in water 1 L acid solution

50433 Fluka DL-Tartaric acid solution for IC, 0.1 M in water 1 L

55517 Fluka Methanesulfonic acid solution for IC, 0.1 M in water 1 L

16355 Fluka Nitric acid solution for IC, 0.1 M in water 1 L

68487 Fluka Oxalic acid solution for IC, 0.1 M in water 1 L

50439 Fluka Perchloric acid solution for IC, 0.01 M in water 1 L

61699 Fluka Potassium hydroxide solution for IC, 0.1 M in water 1 L

36486 Fluka Sodium bicarbonate solution for IC, 0.1 M in water 1 L

56169 Fluka Sodium carbonate solution for IC, 0.1 M in water 1 L

43617 Fluka Sodium hydroxide solution for IC, 0.1 M in water 1 L

68279 Fluka Sulfuric acid solution for IC, 0.1 M in water 1 L

00612 Fluka Water for IC2 2.5 L, 5 L

1 Packaging: HDPE bottles with 45 mm screw-thread cap 2 can also be used for voltammetry

Ion chromatography (IC) is an

analytical technique that is used to

separate and quantify ppm-levels of

common anions (e.g. fluoride,

chloride, nitrite, nitrate, and sufate)

and cations (e.g. ammonium, and

alkali- and earth alkali ions) in

aqueous samples. Separation occurs

via differential interaction with an

ion-exchange resin. Conductivity is

the most common detection

method. The sensitivity of IC makes

it ideal for low ppm level quantifica-

tion and also for trace analysis; thus

IC itself creates the requirement for

high purity eluents and well-defined

standards. As a leading supplier of

high-quality products for all areas of

analytical chemistry, Sigma-Aldrich

has expertise in the production of

standards, eluents, and high purity

water suitable for sensitive ion

determination.

Designed to save IC analysts’ time and to ensure the most sensitive and reproducible

IC determinations, our lines of TraceCERT standards for IC and pre-made Certified

Eluent Concentrates for IC are convenient time and cost-saving options.

The Certified Eluent Concentrates, listed in Table 9, are traceable by potentiometric

titration to NIST Standard Reference Materials and certified in accordance with ISO

Guide 31. All details regarding exact content, uncertainty, traceability, and expiration

date are described in the Certificate of Analysis, which is available electronically on our

Web site: sigma-aldrich.com/IC

To meet your needs for IC analysis, we also offer certified multi-element standards

(PRIMUS) and a new test kit for IQ, OQ, or PQ (Fluka 12674) activities.

Ultra Pure Reagents for VoltammetryTraceSELECT reagents for ultra-trace analysis and metal speciation

Voltammetry is predominantly

used for inorganic trace analysis of

anions and cations, but can also be

used for the determination of

various organic compounds. The

most important fields of application

of inorganic determinations are in

metallurgy, environmental analysis,

food analysis, toxicology, and

clinical analysis. This technique is

also a preferred method for the

determination of certain metal

speciations, such as Fe(II)/Fe(III)

or Cr(III)/Cr(VI).

When mercury is used as an

electrode in a voltammetric cell,

the technique is called polarography. The reduction of metals

into mercury is more favourable than reduction to the solid-

state electrode. Further on there is always a clean new Hg

electrode surface available for each measurement.

Sigma-Aldrich has recently introduced an ultra pure mercury

quality suitable for trace analysis by polarography and three

buffers substances specifically designed for voltammetry and ion

chromatography.

Table 10. High Purity Reagents for Voltammetry*

Cat. No. Brand Product Name Specification Pack sizes

83359 Fluka Mercury for polarography ≥ 99.9995% 5 g, 100 g

94068 Fluka Citric acid monohydrate TraceSELECT 100 g

05878 Fluka L-Ascorbic acid TraceSELECT 100 g

93722 Fluka Oxalic acid dihydrate TraceSELECT 100 g

* Further reagents used for voltammetry are listed in Tables 3 and 4.

1. Henze, G.. Introduction to Polarography and Voltammetry, Metrohm Monograph 60 pages, DIN A 5 format. For a free copy, please contact www.metrohm.com

Multi-mode Electrode (MME)Published with kind permission of Metrohm AG, Switzerland

11sigma-aldrich.com

Calibration for Trace Analysis:TraceCERT - Certified Reference Materials

Following long-lasting coopera-

tion with different metrological

institutes, such as Switzerland’s

EMPA and Germany’s BAM,

Sigma-Aldrich has built-up a

broad knowledge base in the field

of certified reference material

(CRM) production. After two

years of continuous development,

our Buchs facility was ready to be

audited by the Swiss Accreditation

Service and received the highest

achievable quality assurance level

for CRM producers: the double

accreditation as both a testing

laboratory (ISO/IEC 17025) and a

CRM producer (ISO Guide 34).

This combination is also called the

“Gold Standard” accreditation for

CRM producers.

The quality of a CRM strongly depends on the quality of the starting materials

and, therefore, their characterization is very important. TraceCERT starting

materials are characterized by two different approaches: the direct measurement

of the purity by the most accurate method (e.g. titrimetry or high-performance

ICP-OES) and the purity assignment by the “100% minus impurities” approach.

The combination of these two purity assignments leads to two independent

traceability chains, and results in higher reliability of the CRM.

The first products developed and produced under these doubly-accredited

conditions are our TraceCERT calibration standards for spectrometry and ion

chromatography. The name TraceCERT stands for Traceability and CERTified, and

means that these CRMs are suitable for even the most challenging analytical

applications. They also fulfill all the needs of our customers who work in regu-

lated environments.

Key characteristics of these new CRMs are: l Unique level of accuracy and lot-specific values l Produced in doubly-accredited laboratory that fulfills ISO/IEC 17025

and ISO Guide 34 l Traceable to at least two independent references (NIST, BAM or SI unit kg) l Comprehensive documentation according to ISO Guide 31, including

proper uncertainty calculation l Expiration date and storage information l Sophisticated packaging l Competitively priced

More information on issues

related to CRM quality and

production can be obtained by

reading the series of Analytix

articles published in 2006 and

2007: Part 1, Vol. 5 (2006) and

Part 2-5: Vol. 1-4 (2007),

available at sigma-aldrich.com/

analytix. This series covered the

following topics: traceability,

uncertainty, characterization of

high-purity starting materials,

production, packaging and

stability studies.

Visit our Web site on a regular basis, as

we are constantly adding new TraceCERT Standards:

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