IEC 62321-7-2:2017

Determination of certain substances in electrotechnical products - Part 7-2: Hexavalent chromium - Determination of hexavalent chromium (Cr(VI)) in polymers and electronics by the colorimetric method

IEC 62321-7-2:2017 describes procedures to measure hexavalent chromium, Cr(VI), quantitatively in samples of polymers and electronics. This method employs organic solvent to dissolve or swell the sample matrix, followed by an alkaline digestion procedure to extract Cr(VI) from samples. Studies have shown that organic;alkaline solution is more effective than acidic solution in extracting Cr(VI) from soluble and insoluble samples. Minimal reduction of Cr(VI) to Cr(III) or oxidation of Cr(III) to Cr(VI) occurs under alkaline conditions. The first edition of IEC 62321:2008 was a 'stand-alone' standard that included an introduction, an overview of test methods, a mechanical sample preparation as well as various test method clauses. This first edition of IEC 62321-7-2 is a partial replacement of IEC 62321:2008, forming a structural revision and generally replacing Annex C. IEC 62321-7-2 is the final replacement part of the corresponding clauses in IEC 62321:2008.
It has the status of a horizontal standard in accordance with IEC Guide 108 .

Détermination de certaines substances dans les produits électrotechniques - Partie 7-2: Chrome hexavalent - Détermination du chrome hexavalent (Cr(VI)) dans les polymères et les produits électroniques par la méthode colorimétrique

l'IEC 62321-7-2:2017 décrit des procédures de mesure quantitative du chrome hexavalent, Cr(VI), dans des échantillons de polymères et de produits électroniques. Cette méthode emploie un solvant organique destiné à dissoudre ou à faire gonfler la matrice de l'échantillon, puis une procédure de digestion alcaline visant à extraire le chrome hexavalent des échantillons. Des études ont démontré que la solution alcaline/organique est plus efficace que la solution acide pour extraire le Cr(VI) d'échantillons solubles et insolubles. La réduction minimale du Cr(VI) en Cr(III) ou l'oxydation du Cr(III) en Cr(VI) se produit en milieu alcalin.
La première édition de l'IEC 62321:2008 était une norme "autonome" qui comprenait une introduction, une vue d'ensemble des méthodes d'essai, la préparation mécanique d'échantillon, ainsi que différents articles relatifs à des méthodes d'essai. Cette première édition de l'IEC 62321-7-2 remplace en partie l'IEC 62321:2008, constituant une révision structurelle et remplaçant, en général, l'Annexe C. L'IEC 62321-7-2 remplace définitivement les articles correspondants dans l'IEC 62321:2008.
Elle a le statut de norme horizontale conformément au Guide IEC 108.

General Information

• Status: Published
• Publication Date: 27-Mar-2017
• ICS: 31.020 - Electronic components in general
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: TC 111 - Environmental standardization for electrical and electronic products and systems
• Drafting Committee: WG 3 - TC 111/WG 3
• Current Stage: PPUB - Publication issued
• Start Date: 28-Mar-2017
• Completion Date: 27-Mar-2017

Overview

IEC 62321-7-2:2017 is an international standard published by the International Electrotechnical Commission (IEC) that defines precise methods for the determination of hexavalent chromium (Cr(VI)) in polymers and electronic products. This standard is a part of the IEC 62321 series that focuses on the determination of certain hazardous substances in electrotechnical products. The test method described employs a colorimetric procedure, involving extraction of Cr(VI) using organic solvents and alkaline digestion, followed by quantitative measurement with a colorimeter or spectrophotometer.

This method ensures accurate, consistent, and global testing standards for Cr(VI) content in electronic and polymer materials - substances of significant environmental and regulatory concern due to their toxicity and impact on human health.

Key Topics

• Scope and Purpose

  • Quantitative analysis of hexavalent chromium (Cr(VI)) specifically in polymers such as ABS, PC, and PVC, and electronic components.
  • Focus on minimizing chemical changes during sample preparation, ensuring extraction reflects true Cr(VI) content.

• Analytical Procedure

  • Use of an organic solvent to dissolve or swell the sample matrix.
  • Alkaline digestion at elevated temperatures (150-160 °C) for extraction.
  • Separation of organic and inorganic phases in extracts for analysis.
  • Colorimetric detection using 1,5-diphenylcarbazide reagent, forming a red-violet complex measurable at 540 nm wavelength.

• Extraction Efficiency

  • Verification that organic and alkaline solutions provide superior extraction compared to acidic solutions.
  • Minimal oxidation and reduction of chromium species during extraction, maintaining sample integrity.

• Instrumentation

  • Use of colorimeters and spectrophotometers for sensitive and precise measurements.

• Quality Assurance

  • Defined procedures for calibration, calculation, and detection limits.
  • Guidelines for sampling, precision, and spike recovery corrections to ensure reliability of results.

Applications

IEC 62321-7-2:2017 is essential for manufacturers, testing labs, and regulatory bodies involved in:

• Environmental Compliance

  • Ensuring products meet global restrictions on hazardous substances, including RoHS directives and similar international regulations limiting Cr(VI) use.

• Product Safety and Quality Control

  • Routine testing of polymers and electronics to detect and quantify Cr(VI) levels.
  • Supporting safer product design and manufacturing by monitoring chemical additives and impurities.

• Hazardous Substance Management

  • Monitoring electronic waste and recyclability by identifying controlled substances.
  • Supporting environmental impact assessments related to electrotechnical products.

• Research and Development

  • Material testing for innovation in polymer formulations or electronics with reduced toxic substances.

Related Standards

• IEC 62321 Series

  • A collection of standards addressing determination of different harmful substances in electrotechnical products, including heavy metals, flame retardants, and phthalates.

• IEC Guide 108

  • Provides guidelines for horizontal standards like IEC 62321-7-2, applicable broadly across electrotechnical industries.

• RoHS (Restriction of Hazardous Substances) Directives

  • Regional and international regulations that limit the use of hazardous substances including hexavalent chromium in electrical and electronic equipment.

• ISO/IEC Directives, Part 2

  • Standardized procedures for preparing and managing international standards ensuring harmonized global application.

---

Keywords: IEC 62321-7-2, hexavalent chromium, Cr(VI) determination, colorimetric method, polymers, electronics, electrotechnical products, toxic substances, environmental compliance, hazardous substances testing, spectral analysis, polymer testing, electronic product standards, RoHS compliance, colorimeter, spectrophotometer, chemical extraction, alkaline digestion.

Standards Content (Sample)

IEC 62321-7-2 ®
Edition 1.0 2017-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
HORIZONTAL STANDARD
NORME HORIZONTALE
Determination of certain substances in electrotechnical products –
Part 7-2: Hexavalent chromium – Determination of hexavalent chromium (Cr(VI))
in polymers and electronics by the colorimetric method

Détermination de certaines substances dans les produits électrotechniques –
Partie 7-2: Chrome hexavalent – Détermination du chrome hexavalent (Cr(VI))
dans les polymères et les produits électroniques par méthode colorimétrique

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IEC 62321-7-2 ®
Edition 1.0 2017-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
HORIZONTAL STANDARD
NORME HORIZONTALE
Determination of certain substances in electrotechnical products –

Part 7-2: Hexavalent chromium – Determination of hexavalent chromium (Cr(VI))

in polymers and electronics by the colorimetric method

Détermination de certaines substances dans les produits électrotechniques –

Partie 7-2: Chrome hexavalent – Détermination du chrome hexavalent (Cr(VI))

dans les polymères et les produits électroniques par méthode colorimétrique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.020; 71.040.50 ISBN 978-2-8322-4085-4

– 2 – IEC 62321-7-2:2017  IEC 2017

CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviated terms . 6
3.1 Terms and definitions . 6
3.2 Abbreviated terms . 7
4 Reagents . 7
4.1 General . 7
4.2 Reagents . 7
5 Apparatus . 8
5.1 General . 8
5.2 Apparatus . 8
6 Sampling . 9
7 Test procedure . 9
7.1 Extraction of Cr(VI) in soluble polymers – ABS, PC and PVC matrixes . 9
7.2 Extraction of Cr(VI) in insoluble/unknown polymers and electronics − without
Sb . 10
8 Calibration . 11
8.1 Permanent calibration instruments . 11
8.2 Traditional calibration instruments . 11
8.2.1 General . 11
9 Calculation . 12
10 Precision . 13
11 Quality assurance and control . 14
11.1 General method . 14
11.2 Matrix spike recovery correction method . 14
12 Limits of detection (LOD) and limits of quantification (LOQ) . 14
12.1 General . 14
12.2 Determination of LOD and LOQ . 15
13 Test report . 16
Bibliography . 17

Table 1 – Statistical data of all IIS trails . 13
Table 2 – Method detection limit = t × s . 16
n–1
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DETERMINATION OF CERTAIN SUBSTANCES
IN ELECTROTECHNICAL PRODUCTS –

Part 7-2: Hexavalent chromium – Determination of hexavalent chromium
(Cr(VI)) in polymers and electronics by the colorimetric method

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62321-7-2 has been prepared by IEC technical committee 111:
Environmental standardization for electrical and electronic products and systems.
It has the status of a horizontal standard in accordance with IEC Guide 108.
The first edition of IEC 62321:2008 was a ‘stand-alone’ standard that included an introduction,
an overview of test methods, a mechanical sample preparation as well as various test method
clauses.
This first edition of IEC 62321-7-2 is a partial replacement of IEC 62321:2008, forming a
structural revision and generally replacing Annex C. IEC 62321-7-2 is the final replacement
part of the corresponding clauses in IEC 62321:2008.

– 4 – IEC 62321-7-2:2017  IEC 2017
The text of this standard is based on the following documents:
CDV Report on voting
111/408/CDV 111/432/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62321 series, published under the general title Determination of
certain substances in electrotechnical products, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
INTRODUCTION
The widespread use of electrotechnical products has drawn increased attention to their impact
on the environment. In many countries all over the world this has resulted in the adaptation of
regulations affecting wastes, substances and energy use of electrotechnical products.
The use of hexavalent chromium in electrotechnical products is of concern in many regions of
the world.
The purpose of this document is therefore to provide test methods that will allow the
electrotechnical industry to determine the levels of hexavalent chromium in electrotechnical
products on a consistent global basis.
WARNING – Persons using this document should be familiar with normal laboratory practice.
This document does not purport to address all of the safety problems, if any, associated with
its use. It is the responsibility of the user to establish appropriate safety and health practices
and to ensure compliance with any national regulatory conditions.

– 6 – IEC 62321-7-2:2017  IEC 2017
DETERMINATION OF CERTAIN SUBSTANCES
IN ELECTROTECHNICAL PRODUCTS –

Part 7-2: Hexavalent chromium – Determination of hexavalent chromium
(Cr(VI)) in polymers and electronics by the colorimetric method

1 Scope
This part of IEC 62321 describes procedures to measure hexavalent chromium, Cr(VI),
quantitatively in samples of polymers and electronics. This method employs organic solvent to
dissolve or swell the sample matrix, followed by an alkaline digestion procedure to extract
Cr(VI) from samples. Studies have shown that organic/alkaline solution is more effective than
acidic solution in extracting Cr(VI) from soluble and insoluble samples. Minimal reduction of
Cr(VI) to Cr(III) or oxidation of Cr(III) to Cr(VI) occurs under alkaline conditions.
For soluble polymers consisting of ABS (Acrylonitrile- butadiene-styrene), PC (Polycarbonate)
and PVC (poly(vinyl chloride)), the samples are first dissolved in an appropriate organic solvent
and Cr(VI) is then extracted by an alkaline extraction solution.
For insoluble/unknown polymers, or electronic materials that do not contain antimony (Sb),
the samples are digested in a toluene/alkaline solution at 150 °C to 160 °C. Then the organic
phase in the extracts are separated and discarded; the inorganic phase is retained for Cr(VI)
analysis.
The Cr(VI) concentration in the extract is determined by its reaction under acidic conditions
with 1,5-diphenylcarbazide. Cr(VI) is reduced to Cr(III) in the reaction with diphenylcarbazide
which is oxidized to diphenylcarbazone. The Cr(III) and diphenylcarbazone form a red-violet-
coloured complex in the reaction. The complex solution is measured quantitatively by a
colorimeter or a spectrophotometer at 540 nm.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 62321-1, Determination of certain substances in electrotechnical products – Part 1:
Introduction and overview
ISO 3696, Water for analytical laboratory use – Specification and test methods
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62321-1 apply.

ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.2 Abbreviated terms
For the purposes of this document, the abbreviated terms given in IEC 62321-1 apply.
4 Reagents
4.1 General
Use only reagents of recognized analytical grade, unless otherwise specified.
4.2 Reagents
The following reagents shall be used:
a) N-Methyl-pyrrolidone (NMP), analytical reagent grade. Add 10 g activated molecular
sieves (4.2 r)) per 100 ml of newly opened NMP, seal the cap tightly, keep in the dark,
shake occasionally and maintain over 12 h before first use. Store at 20 °C to 25 °C with
molecular sieves in a tightly sealed brown glass container and avoid direct light exposure.
The suggested maximum storage period is four weeks after the opening time of the
container.
b) Nitric acid, volume fraction of 35 %. Dilute 50 ml of reagent grade HNO to 100 ml with
water (see 4.2 p)) in a volumetric flask (5.2 j)). Store at 20 °C to 25 °C in the dark. Do not
use concentrated HNO if it has a yellow colour, which is an indication of photoreduction
- -
of NO to NO , a reducing agent for Cr(VI).
3 2
c) Sodium carbonate: Na CO , anhydrous, analytical reagent grade.
2 3
d) Sodium hydroxide: NaOH, analytical reagent grade.
e) Magnesium chloride: MgCl (anhydrous), analytical reagent grade. A mass of 200 mg
2+
MgCl is approximately equivalent to 50 mg Mg .
f) Phosphate buffer. To prepare a buffer solution at pH 7, dissolve 87,09 g K HPO
2 4
(analytical reagent grade) and 68,04 g KH PO (analytical reagent grade) into 700 ml of
2 4
water (4.2 p)). Transfer to a 1 l volumetric flask (5.2 j)) and dilute to volume. As prepared,
the solution will contain 0,5 mol/l K HPO and 0,5 mol/l KH PO .
2 4 2 4
g) Lead chromate: PbCrO , analytical reagent grade. Store at 20 °C to 25 °C in a tightly
sealed container. This is the agent used for the matrix spike recovery correction method.
h) Digestion solution. Dissolve 20,0 g ± 0,05 g NaOH and 30,0 g ± 0,05 g Na CO in water
2 3
(4.2 p)) in a 1 l volumetric flask (5.2 j)) and dilute to the mark. Store the solution in a
tightly capped polyethylene bottle at 20 °C to 25 °C, and prepare fresh monthly. The pH of
the digestion solution shall be checked before using. If the pH is < 11,5 discard the
solution and prepare a fresh batch.
i) Toluene, analytical reagent grade.
j) Potassium dichromate stock solution. Dissolve 141,4 mg of dried (105 °C) K Cr O
2 2 7
(analytical reagent grade) in water (4.2 p)) and dilute to 1 l in a volumetric flask (5.2 j))
(1 ml contains 50 µg Cr).
k) Potassium dichromate standard solution. Dilute 10 ml potassium dichromate stock solution
(4.2 j)) with water (4.2 p)) to 100 ml in a volumetric flask (5.2 j)) (1 ml contains 5 µg Cr).
l) Sulfuric acid, volume fraction of 10 %. Dilute 10 ml of distilled reagent grade or
spectroscopic grade H SO to 100 ml with water (4.2 p)) in a volumetric flask (5.2 j)).
2 4
m) Diphenylcarbazide solution. Dissolve 250 mg 1,5-diphenylcarbazide in 50 ml acetone
(4.2 q)). Store in a brown bottle. Prior to use, check the solution for discoloration. Store for

– 8 – IEC 62321-7-2:2017  IEC 2017
use up to two weeks and if solution becomes discoloured, discard it and prepare a fresh
batch.
n) Potassium dichromate, K Cr O , spike solution 1 000 mg/l Cr(VI)). Dissolve 2,829 g of
2 2 7
dried (105 °C) K Cr O in water (4.2 p)) in a 1 l volumetric flask (5.2 j)), and dilute to the
2 2 7
mark. Alternatively, a 1 000 mg/l Cr(VI)-certified standard solution can be used. Store for
use up to six months at 20 °C to 25 °C in a tightly sealed container.
o) Potassium dichromate, K Cr O , matrix spike solution (100 mg/l Cr(VI)): Add 10,0 ml of
2 2 7
the 1 000 mg/l Cr(VI) solution made from K Cr O spike solution (4.2 n)) to a 100 ml
2 2 7
volumetric flask (5.2 j)) and dilute to volume with water (4.2. p)). Mix well.
p) Water. Grade 3 specified in ISO 3696, which shall be free of interferences.
q) Acetone, analytical reagent grade.
r) Molecular sieves (4A), CAS: 70955-01-0, desiccant.
WARNING – All potential Cr(VI)-containing samples and reagents used in the method have to
be handled with appropriate precautions. Solutions or waste material containing Cr(VI) have
to be disposed of properly. For example, ascorbic acid or some other reducing agents can be
used to reduce Cr(VI) to Cr(III).
5 Apparatus
5.1 General
All re-usable laboratory ware (glass, quartz, polyethylene, polytetrafluoroethylene (PTFE),
etc.) including the sample containers shall be soaked overnight in laboratory-grade detergent
and water, rinsed with water, and soaked for 4 h or more in HNO (volume fraction of 20 %) or
in a mixture of dilute acids (HNO :HCl:H O = 1:2:9 by volume) followed by rinsing with water
3 2
(4.2 p)). Alternative cleaning procedures are permitted, provided adequate cleanliness can be
demonstrated through the analysis of method blanks.
5.2 Apparatus
The following items shall be used for the analysis:
a) Vacuum filtration apparatus.
b) Heating or microwave device capable of maintaining the digestion solution at
temperatures between 150 °C and 160 °C.
c) Ultrasonic water bath, capable of maintaining the temperature between 60 °C and 65 °C.
d) Calibrated pH meter to read pH in a range of 0 to 14 with an accuracy of ±0,03 pH units.
e) Analytical balance capable of measurement to 0,1 mg.
f) Thermometer, thermistor or other temperature measurement device capable of measuring
up to 160 °C.
g) Colorimetric instrument: either a spectrophotometer for use at 540 nm, providing a light
path of 1 cm or longer or a filter photometer, providing a light path of 1 cm or longer and
equipped with a filter having maximum transmittance near 540 nm.
h) Grinding mill, with or without liquid nitrogen cooling, capable of grinding polymer samples
and electronic components.
i) Borosilicate glass or quartz beaker with volume graduation of 150 ml, or equivalent.
j) Volumetric glassware: Class A or equivalent of acceptable precision and accuracy.
Alternative volumetric equipment (e.g. automatic dilutors) with equivalent precision and
accuracy can be used.
k) Assorted calibrated pipettes: Class A glassware or other with equivalent precision and
accuracy.
l) Digestion vessel: Glass screw thread bottle (wide neck), volume of 50 ml and minimum
inner diameter of 3 cm.
m) Glass separatory funnel, 100 ml.
n) Filter membranes (0,45 µm): preferably cellulose-based or PC membranes; filter syringe
(0,45 µm): nylon or PVDF.
o) C18 syringe filter cartridge.
p) Microwave digestion vessel or a suitable borosilicate glass or quartz vessel equipped with
a membrane for pressure relief over 1,0 MPa and volume graduation of 50 ml or
equivalent.
6 Sampling
Samples shall be collected and stored using devices and containers that do not contain
stainless steel.
For soluble polymers (ABS, PC and PVC), a particle size larger than 250 µm is acceptable,
however, a longer dissolution time may be required to completely dissolve the polymer matrix.
Insoluble or unknown polymers and electronic components that do not contain Sb shall be
ground into a fine powder (5.2. h)) prior to digestion to promote extraction, with 100 % of the
material passing through a 250 µm sieve, for example a No. 60 ASTM standard sieve.
If the identity of the polymer matrix is unknown, a solubility test can be performed by testing a
small amount of the sample using an organic solvent. Alternatively, infrared spectroscopy (IR)
can be performed to identify the bulk polymer. The presence of Sb can be detected by X-ray
fluorescence spectroscopy (XRF).
7 Test procedure
7.1 Extraction of Cr(VI) in soluble polymers – ABS, PC and PVC matrixes
a) Accurately weigh a sample of 0,1 g. Place the sample into a digestion vessel (5.2. l)).
NOTE Alternative sample amounts can be used for samples with potentially very low or very high Cr(VI)
concentrations.
b) Place 10 ml of NMP (4.2. a)) into the digestion vessel (5.2. l)) and seal the cap tightly.
c) Dissolve each polymer sample by ultrasonication (5.2 c)) at 60 °C for 1 h. Shake the
sample vessel by hand for about 10 s to suspend insoluble particles, then ultrasonicate at
60 °C for 1 h again. The sample matrix has to be completely dissolved before proceeding
to the next step.
d) To test for recovery in every matrix, accurately weigh a second sample of 0,1 g (or
another chosen amount of sample). Place it into the digestion vessel (5.2. l)) and add 10
ml of NMP (4.2 a)) into the vessel and seal the cap tightly. Then proceed with step 7.1 c),
choose a matrix spike solution (4.2 o)) and add it directly to the sample. Follow steps from
7.1 e) to 7.1 o).
e) Shake the digestion vessel by hand and mix well, then add 200 mg MgCl (4.2 e)) and
0,5 ml of 0,5 mol/L phosphate buffer (4.2 f)) to each digestion vessel. Shake the digestion
vessel again and mix well.
f) Measure 20 ml of the digestion solution (4.2 h)) using a graduated cylinder (5.2 j)) and
slowly pour into each digestion vessel (5.1 l)). Mix well.
g) Ultrasonicate above solution at 60 °C for 1 h (shake the digestion vessel by hand and mix
well after 0,5 h).
h) Transfer above content to a 150 ml beaker (5.2 i)). With constant stirring while monitoring
the pH, add HNO (4.2 b)) dropwise to the beaker. Adjust the pH of the solution to
7,5 ± 0,5.
i) Even if the sample solution is turbid or flocculent precipitates are present, do not filter the
sample solution.
– 10 – IEC 62321-7-2:2017  IEC 2017
j) Add 2,5 ml diphenylcarbazide solution (4.2 m)) to each vessel. Slowly add H SO solution
2 4
(4.2 l)) to the vessel and adjust the pH of the solution to 2,0 ± 0,5.
k) Transfer the contents of the vessel quantitatively to a 100 ml volumetric flask (5.2 j)) and
make up to the mark by water (4.2 p)). Mix well.
l) Filter the coloured sample solution using the 0,45 µm syringe filter (5.2 n)).
m) Transfer an appropriate portion of the solution to a 1 cm absorption cell and measure its
absorbance at 540 nm with a colorimetric instrument (5.2 g)). Measurement shall be taken
within 30 min of colour development.
n) Correct the absorbance reading of the sample by subtracting the absorbance of a blank
carried through the colour development procedures.
o) From the corrected absorbance, determine the concentration of Cr(VI) present by referring
to the calibration curve.
7.2 Extraction of Cr(VI) in insoluble/unknown polymers and electronics − without Sb
a) Accurately weigh a sample of 0,15 g. Place the sample into a digestion vessel (5.2 p)).
NOTE Alternative sample amounts can be used for samples with potentially very low or very high Cr(VI)
concentrations.
b) To each sample add 10 ml of digestion solution (4.2 h)) and 5 ml of toluene (4.2 i))
measured with a graduated cylinder (5.2 j)).
c) To test for recovery in every matrix, accurately weigh a second sample of 0,15 g and
place it into a second digestion vessel (5.2 p)). Choose a spike solution (4.2 n) or 4.2 o))
and add it directly to the sample. Add 10 ml of digestion solution (4.2 h)) and 5 ml of
toluene (4.2 i)) measured with a graduated cylinder (5.2 j)).
d) Next, add 400 mg MgCl (4.2 e)) and 0,5 ml of 1,0 mol/L phosphate buffer (4.2 f)) to each
sample and mix well.
MgCl is added to the solution to correct possible oxidation/reduction of chromium that
may be caused by the analytical method.
e) Heat each sample to a temperature of 150 °C to 160 °C in a closed digestion vessel
(5.2 p)) using a microwave oven or suitable heating device (5.2 b)). Then maintain
temperature at 150 °C to 160 °C for 1,5 h and allow sample to cool to room temperature.
f) Separate the organic phase from the vessel using a separatory funnel (5.2 m)) and
discard it. The aqueous phase is filtered through a 0,45 µm membrane filter (5.2 n)).
Rinse the digestion vessel (5.2 p)) three times with water (4.2 p)) and filter. If the filter
becomes clogged using the 0,45 µm membrane filter; a large pore size filter paper may be
used to filter the samples.
g) Rinse the inside of the filter flask and the filter pad with water (4.2 p)) and transfer the
filtrate and the rinse solutions to a clean 150 ml beaker (5.2. i)).
h) With constant stirring while monitoring the pH, add HNO (4.2 b)) dropwise to the vessel
obtained in 7.2 g). Adjust the pH of the solution to 7,5 ± 0,5.
i) If the sample solution is clear after pH adjustment, add 2,5 ml diphenylcarbazide solution
(4.2 m)) to each vessel. Slowly add H SO solution (4.2 l)) to the vessel and adjust the pH
2 4
of the solution to 2,0 ± 0,5. Proceed with step 7.2 l). If the solution is turbid or contains a
flocculent precipitate (cloudy, flake-like and non-crystalline), or colour is present, proceed
to 7.2 j).
j) If the solution is turbid or flocculent precipitates are present, filter the sample through a
0,45 µm membrane filter (5.2 n)). If colour is present in the sample solution, filter the
solution with a C18 syringe cartridge (5.2 o)) before adding diphenylcarbazide solution
(4.2 m)). If the digestate is clear after either filtration step, add 2,5 ml diphenylcarbazide
solution (4.2 m)) to the vessel. Slowly add H SO solution (4.2 l)) to the vessel and adjust
2 4
the pH of the solution to 2,0 ± 0,5. Proceed to 7.2 l). If the digestate is coloured or turbid
SO solution (4.2 l)) to the vessel and adjust the
after either filtration step, slowly add H
2 4
pH of the solution to 2,0 ± 0,5. Proceed to 7.2.k).
k) Transfer each of the coloured or turbid digestates quantitatively to a 50 ml volumetric flask
(5.2 j)) and adjust to volume with water (4.2 p)). Invert several times to mix. Remove

approximately 5 ml from the flask and record an absorbance reading via a colorimetric
instrument (5.2 g)) for background subtraction. Add 2,5 ml diphenylcarbazide solution
(4.2 m)) to each sample digestion solution, mix and adjust the sample volumes to 50 ml
with water (4.2 p)). Invert several times to mix and let stand 5 min to 10 min for full colour
development. Proceed to 7.2.l).
l) Transfer the contents of the vessel quantitatively to a 50 ml volumetric flask (5.2 j)) and
adjust the sample volume to 50 ml with water (4.2 p)). Invert several times to mix and let
stand 5 min to 10 min for full colour development.
m) Transfer an appropriate portion of the solution to a 1 cm absorption cell and measure its
absorbance at 540 nm with a colorimetric instrument (5.2 g)). The analysis has to be
carried out as soon as possible, with a maximum delay of 30 min, after extraction.
n) Correct the absorbance reading of the sample by subtracting the absorbance of a blank
carried through the colour development procedures. For the coloured or turbid solutions
after either filtration in 7.2 j), correct the absorbance by subtracting the absorbance
reading from step 7.2 k).
o) From the corrected absorbance, determine the concentration of Cr(VI) present by referring
to the calibration curve.
8 Calibration
8.1 Permanent calibration instruments
Colorimetric instruments designed specifically for hexavalent chromium detection at 540 nm
may have a permanent calibration provided by the manufacturer and no further calibration is
needed. Refer to the manufacturer’s instructions to ensure that the instrument is functioning
properly and its working range is appropriate for this analysis.
8.2 Traditional calibration instruments
8.2.1 General
Traditional colorimetric instrument calibration shall be conducted using a blank and three
standard solutions at a minimum.
Zero the colorimetric instrument with the 0,0 µg/ml blank standard and save this solution to
re-zero the instrument before reading samples and standards.
Read the standard solutions. Construct a calibration curve and determine a line equation by
plotting absorbance values (ordinate or y-axis) against µg/ml of Cr(VI) (abscissa or x-axis) for
each standard including the 0,0 µg/ml standard.
Routinely the calibration curves can be used for up to one month from initial generation.
Internal check with a calibration standard should be carried out every day for quality control.
a) For preparation of the calibration standards, the matrix should be the same as the sample
solution. After the step of digestion (7.1 g) or 7.2 g)), add a suitable volume of Cr(VI)
standard solution (4.2 j)). Use the Cr(VI) standard solution (4.2 j)) to create concentrations
ranging from 0,1 mg/l to 1,0 mg/l Cr(VI). Prepare a blank and a minimum of three standard
solutions.
An alternative concentration range of the standard solutions can be used if the Cr(VI)
concentration in the sample solution is outside the original calibration curve. The sample
solutions can also be diluted if they are more concentrated than the highest calibration
solution. Additionally, in the cases where the base polymer without Cr(VI) are available, it
is recommended to prepare the calibration standards with the base polymer to achieve the
closest matrix calibration match.
b) With constant stirring while monitoring the pH, add HNO (4.2 b)) dropwise to the vessel
obtained in 7.2 g). Adjust the pH of the solution to 7,5 ± 0,5.

– 12 – IEC 62321-7-2:2017  IEC 2017
c) Add 2,5 ml diphenylcarbazide solution (4.2 m)) to each vessel. Slowly add H SO solution
2 4
(4.2 l)) to the vessel and adjust the pH of the solution to 2,0 ± 0,5.
d) Transfer the contents of the vessel quantitatively to a 50 ml volumetric flask (5.2 j)) and
adjust the sample volume to 50 ml with water (4.2 p)). Invert several times to mix and let
stand 5 min to 10 min for full colour development.
e) Transfer an appropriate portion of the solution to a 1 cm absorption cell and measure the
absorbance at 540 nm using the colorimetric instrument (5.2 g)).
f) Correct the absorbance reading by subtracting the absorbance of a blank carried through
the colour development procedure.
g) Construct a calibration curve by plotting corrected absorbance values versus
concentration of Cr(VI). Either linear regression or quadratic fitting can be applied to
establish a calibration curve. The correlation coefficient (R2) of the curve shall be > 0,995
or a new calibration curve shall be created.
9 Calculation
The concentration of Cr(VI) shall be calculated according to Formula (1):
A×D ×F
C = (1)
S
where
C is the total sample Cr(VI) concentration in µg/g;
A is the Cr(VI) concentration observed in the digestate in µg/ml; or µg/g;
D is the dilution factor;
F is the final volume of the digestate in ml; or the final mass of the digestate in g;
S is the initial sample mass in g.
The relative percent difference shall be calculated according to Formula (2):
S −D
R = ×100 (2)
0,5 × (S +D)
where
R is the relative percent difference in %;
S is the Cr(VI) concentration in the sample observed in the initial test in µg/g;
D is the Cr(VI) concentration in the sample observed in the duplicated test in µg/g.
NOTE 1 A similar calculation listed in Formula (1) can also be used to obtain the Cr(VI) concentrations in the
initial and duplicated tests.
The spike recovery shall be calculated according to Formula (3):
SS −US
SR = ×100 (3)
SA
where
SR is the spike percent recovery in %;
SS is the Cr(VI) concentration in the spiked sample in µg/g;
US is the Cr(VI) concentration in the unspiked sample in µg/g;
SA is the Cr(VI) concentration used in the spike solution in µg/g.

NOTE 2 Formula (1) can also be used to obtain the Cr(VI) concentrations in the spiked/unspiked sample.
10 Precision
An international inter-laboratory study (IIS) organized by IEC TC 111 during the development
of this method found that Cr(VI) extraction is strongly affected by the sample matrix and the
+3
presence of antimony (particularly Sb ). The suitability of this method is therefore variable
and dependent on the specific compositional matrix of the sample under test. The IIS
exhibited a wide range of results for four polymer types containing levels of Cr(VI) between
106 µg/g and 1 325 µg/g. Results for all materials exhibited reproducibility from 2,8 % up to
5,7 % relative standard deviation.
• Four laboratories submitted triplicate results for an ABS sample (IIS4C-A1) containing
Cr(VI) as well as antimony. All twelve results correlated well with the expected value.
• Two laboratories submitted triplicate results for an ABS sample (IIS4C-B2) containing
Cr(VI). All six results correlated well with the expected value.
• Two laboratories submitted triplicate results for a PC sample (IIS4C-C3) containing Cr(VI).
All six results correlated well with the expected value.
• Four laboratories submitted triplicate results for a PC sample (IIS4C-D4) containing Cr(VI)
as well as antimony. Eleven out of the twelve results correlated well with the expected
value.
• Six laboratories submitted triplicate results for a PVC sample (IIS4C-E5) containing Cr(VI).
All eighteen results correlated well with the expected value.
• Six laboratories submitted triplicate results for a PVC sample (IIS4C-F6) containing Cr(VI)
as well as antimony. All eighteen results correlated well with the expected value.
• Five laboratories submitted triplicate results for a PP sample (IIS4C-G7) containing Cr(VI).
Fourteen out of the fifteen results correlated well with the expected value.
• Six laboratories submitted triplicate results for a PP sample (IIS4C-H8) containing Cr(VI).
All eighteen results correlated well with the expected value.
The statistical data of all trails are summarized in Table 1.
Table 1 – Statistical data of all IIS trails
Sample Analyte Mean value Expected Number of Repeata- Repeata- Reproduci- Reprodu- Number of
value test results bility bility bility cibility partici-
standard standard pating
deviation deviation laboratories
mg/kg mg/kg [n] mg/kg mg/kg mg/kg mg/kg [n]
IIS4C-A1
Cr(VI) 1 028 1 082 12 61,9 173,4 109,3 306,2 4
(ABS/Sb)
IIS4C-B2
Cr(VI) 760 787 6 21,0 58,8 30,7 85,9 2
(ABS)
IIS4C-C3
Cr(VI) 716 803 6 22,6 63,4 25,6 71,6 2
(PC)
IIS4C-D4
Cr(VI) 983 1 043 11 40,5 113,4 127,2 356,1 4
(PC/Sb)
IIIS4C-E5
Cr(VI) 1 281,4 1 300 18 45,1 126,2 346,7 970,9 6
(PVC)
IIS4C-F6
Cr(VI) 425,5 418,8 18 17,5 49,1 86,3 241,6 6
(PVC/Sb)
IIS4C-G7
Cr(VI) 91,1 106 14 3,9 10,9 15,7 43,9 5
(PP)
IIS4C-H8
Cr(VI) 888,1 1 325 15 40,8 114,3 147,6 413,4 5
(PP)
– 14 – IEC 62321-7-2:2017  IEC 2017
11 Quality assurance and control
11.1 General method
Samples shall be analysed in batches of not more than 20 samples counting all samples, any
blanks, any duplicates and any spike recovery tests. A minimum of one blank per batch shall
be prepared and analysed to test for contamination and memory effects. In every batch, at
least one sample shall be prepared in duplicate. Results for duplicate samples shall have a
relative difference of ≤ 20 % or the batch shall be re-analysed. A laboratory control sample
shall be analysed at a frequency of one per batch.
11.2 Matrix spike recovery correction method
Because this test method is subject to relatively strong matrix effects, it is necessary to
demonstrate the matrix spike recovery for every sample having a unique origin. Unique origin
includes any of the following circumstances: different customer (even if same polymer as prior
sample); different production batch (even if same polymer as prior sample); different polymer;
different additives (even if same polymer as prior sample) and all other cases of changes in
sample origin. The matrix spike recovery test begins with spiking the sample prior to
digestion, carrying the spike through the digestion and colour development.
a) A pre-digestion matrix spike sample sha
...