IEC 62321-7-1:2015

IEC 62321-7-1 ®
Edition 1.0 2015-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
HORIZONTAL STANDARD
NORME HORIZONTALE
Determination of certain substances in electrotechnical products –
Part 7-1: Hexavalent chromium – Presence of hexavalent chromium (Cr(VI)) in
colourless and coloured corrosion-protected coatings on metals by the
colorimetric method
Détermination de certaines substances dans les produits électrotechniques –
Partie 7-1: Chrome hexavalent – Présence de chrome hexavalent (Cr(VI)) dans
les revêtements incolores et colorés de protection anticorrosion appliqués sur
les métaux à l'aide de la méthode colorimétrique

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IEC 62321-7-1 ®
Edition 1.0 2015-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
HORIZONTAL STANDARD
NORME HORIZONTALE
Determination of certain substances in electrotechnical products –

Part 7-1: Hexavalent chromium – Presence of hexavalent chromium (Cr(VI)) in

colourless and coloured corrosion-protected coatings on metals by the

colorimetric method
Détermination de certaines substances dans les produits électrotechniques –

Partie 7-1: Chrome hexavalent – Présence de chrome hexavalent (Cr(VI)) dans

les revêtements incolores et colorés de protection anticorrosion appliqués sur

les métaux à l'aide de la méthode colorimétrique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 13.020; 43.040.10 ISBN 978-2-8322-2895-1

– 2 – IEC 62321-7-1:2015 © IEC 2015
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviations . 7
3.1 Terms and definitions . 7
3.2 Abbreviations . 7
4 Reagents . 7
4.1 General . 7
4.2 Reagents . 7
5 Apparatus . 7
5.1 General . 7
5.2 Apparatus . 7
6 Sampling . 8
7 Boiling water extraction procedure . 8
8 Calibration . 11
8.1 Permanent calibration instruments . 11
8.2 Traditional calibration instruments . 11
9 Calculation . 11
10 Precision . 12
11 Quality assurance and control . 12
11.1 Colorimetric instrument performance verification . 12
11.2 Limits of detection (LOD) and limits of quantification (LOQ) . 12
12 Test report . 13
Annex A (informative) International inter-laboratory study on corrosion-protected
coatings – Data overview . 16
Bibliography . 18

Figure 1 – Screw body and screw head measurements . 9
Figure A.1 – Concentration of chromium VI based on surface area for all samples . 16
Figure A.2 – Concentration of chromium VI based on surface area – Expanded view
2 2
between 0 µg/cm to 1 µg/cm . 17

Table 1 – Comparison to standard solution and interpretation of results . 11
Table 2 – Student’s t values used for calculation of method detection limit (LOD or
MDL = t-statistic × standard deviation (sn-1)) . 13
Table 3 – Reporting table . 14
Table 4 – Example of a completed reporting table . 15

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DETERMINATION OF CERTAIN SUBSTANCES
IN ELECTROTECHNICAL PRODUCTS –

Part 7-1: Hexavalent chromium – Presence of hexavalent chromium (Cr(VI))
in colourless and coloured corrosion-protected coatings
on metals by the colorimetric method

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
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interested IEC National Committees.
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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 62321-7-1 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 62321-7-1 is a partial replacement of IEC 62321:2008, forming a
structural revision and generally replacing informative Annex B.
Future parts in the IEC 62321 series will gradually replace the corresponding clauses in
IEC 62321:2008. Until such time as all parts are published, however, IEC 62321:2008 remains
valid for those clauses not yet re-published as a separate part.

– 4 – IEC 62321-7-1:2015 © IEC 2015
The text of this standard is based on the following documents:
FDIS Report on voting
111/380/FDIS 111/393/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62321 series can be found on the IEC website under the general
title: Determination of certain substances in electrotechnical products.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
INTRODUCTION
The widespread use of electrotechnical products has drawn increased attention to their impact
on the environment. In many countries this has resulted in the adaptation of regulations
affecting wastes, substances and energy use of electrotechnical products.
The use of certain substances (e.g. lead (Pb), cadmium (Cd) and polybrominated
diphenylethers (PBDE’s)) in electrotechnical products is a source of concern in current and
proposed regional legislation.
The purpose of the IEC 62321 series is therefore to provide test methods that will allow the
electrotechnical industry to determine the levels of certain substances of concern in
electrotechnical products on a consistent global basis.
WARNING – Persons using this International Standard should be familiar with normal
laboratory practice. This standard 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 62321-7-1:2015 © IEC 2015
DETERMINATION OF CERTAIN SUBSTANCES
IN ELECTROTECHNICAL PRODUCTS –

Part 7-1: Hexavalent chromium – Presence of hexavalent chromium (Cr(VI))
in colourless and coloured corrosion-protected coatings
on metals by the colorimetric method

1 Scope
This part of IEC 62321 describes a boiling water extraction procedure intended to provide a
qualitative determination of the presence of hexavalent chromium (Cr(VI)) in colourless and
coloured corrosion-protection coatings on metallic samples.
Due to its highly reactive nature, the concentration of Cr(VI) in a corrosion-protection coating
can change drastically with time and storage conditions. Since storage conditions prior to
sample submission are not often known or provided with the samples, this procedure
determines the presence of Cr(VI) based on the levels detected in the coatings at the time of
testing. For testing of freshly coated samples, a minimum waiting period of 5 days (after the
coating process) is necessary to ensure the coatings have stabilized. This waiting period
allows potential post-process oxidation of Cr(III) to Cr(VI) to occur prior to testing.
The presence of Cr(VI) is determined by the mass of Cr(VI) per surface area of the coating,
in µg/cm . This approach is preferred since corrosion-protection coating weights are often
difficult to measure accurately after production. From a coating technology perspective, the
industry as a whole has transitioned to either using the non-Cr(VI) based chemistries – where
little to no Cr(VI) should be present – or using the traditional Cr(VI) based chemistries –
where significant levels of Cr(VI) are present and can be detected reliably. Given this industry
shift, the presence or absence of Cr(VI) is often sufficient for compliance testing purposes.
In this procedure, when Cr(VI) in a sample is detected below the 0,10 µg/cm LOQ (limit of
quantification), the sample is considered to be negative for Cr(VI). Since Cr(VI) may not be
uniformly distributed in the coating even within the same sample batch, a “grey zone” between
2 2
0,10 µg/cm and 0,13 µg/cm has been established as “inconclusive” to reduce inconsistent
results due to unavoidable coating variations. In this case, additional testing may be
necessary to confirm the presence of Cr(VI). When Cr(VI) is detected above 0,13 µg/cm , the
sample is considered to be positive for the presence of Cr(VI) in the coating layer.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. 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
IEC 62321-2, Determination of certain substances in electrotechnical products – Part 2:
Disassembly, disjointment and mechanical sample preparation
ISO 78-2, Chemistry – Layouts for standards – Part 2: Methods of chemical analysis
ISO 3696, Water for analytical laboratory use – Specification and test methods

3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62321-1 apply.
3.2 Abbreviations
For the purposes of this document, the abbreviations 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) 1,5-diphenylcarbazide, analytical reagent grade.
b) Potassium dichromate (K Cr O ) stock solution: in a glass container, weigh (5.2 a)) and
2 2 7
dissolve 0,113 g of K Cr O (analytical reagent grade, dried at 100 °C for 1 h before use)
2 2 7
in water (4.2 f)) and dilute with water (4.2 f)) to the mark of a 1,000 ml volumetric flask
(5.2 e)). Cap or stopper the container tightly. The shelf life of this solution is one year.
Cr O ) equivalent comparison standard solutions, 0,10 µg/cm
c) Potassium dichromate (K
2 2 7
and 0,13 µg/cm : in this method, the 0,10 µg/ml and 0,13 µg/ml standards are equivalent
2 2 2
to 0,10 µg/cm and 0,13 µg/cm , respectively. Prepare the 0,10 µg/cm equivalent
comparison standard by pipetting (5.2 f)) 2,5 ml of the K Cr O stock solution (4.2 b)) into
2 2 7
a 1,000 ml volumetric flask and dilute to mark. Prepare the 0,13 µg/cm comparison
standard by pipetting (5.2 f)) 3,3 ml of the K Cr O stock solution (4.2 b)) into a 1,000 ml
2 2 7
volumetric flask (5.2 e)) and dilute to mark.
d) Acetone, analytical reagent grade.
e) Orthophosphoric acid (H PO ) solution (mass fraction of 75 %), analytical reagent grade.
3 4
f) Water: Grade 1 specified in ISO 3696, which shall be free of interferences.
5 Apparatus
5.1 General
All re-usable labware (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 (4.2
3 2
f)). 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) Analytical balance with an accuracy of 0,10 mg.
b) Thermometer or other temperature measurement device capable of measuring up to
100 °C.
– 8 – IEC 62321-7-1:2015 © IEC 2015
c) 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 greenish-yellow filter having maximum transmittance near 540 nm.
d) Boiling chips.
e) 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.
f) Assorted calibrated pipettes: Class A glassware or other with equivalent precision and
accuracy.
g) Borosilicate glass or quartz beaker with a volume graduation of 250 ml, or equivalent.
h) Heating device: capable of maintaining boiling of the extraction solution.
i) Filter membranes (0,45 µm), cellulose-based or polycarbonate types preferred.
j) Silicon carbide (SiC) grinding paper with 800 grit size, or equivalent.
k) Watch glass.
6 Sampling
Samples shall not be stored in environments where oxidation of Cr(III) to Cr(VI) can occur.
Samples shall be stored at ambient conditions upon arrival until the start of testing. Ambient
conditions are defined as 45 % RH to 75 % RH (relative humidity) and temperature between
15 °C and 35 °C.
In some cases, disassembly or mechanical disjointment may be necessary to obtain samples
for testing; refer to IEC 62321-2 for sample preparation.
Prior to the test, the sample surface shall be free of all contaminants, fingerprints and stains.
If the surface is coated with thin oil, the oil shall be removed prior to the test by using a clean,
soft laboratory wipe wetted with a suitable solvent, or by rinsing the surface with a suitable
solvent at ambient temperature. The samples shall not be subject to forced drying at
temperature in excess of 35 °C. Treatment in alkaline solutions shall not be performed as
corrosion-protection coatings are broken down by alkalis.
If there is a polymer coating on a sample surface, gentle abrasion with a fine grinding paper
(5.2 j)) may be performed to expose the corrosion protection layer for extraction; however,
care shall be taken not to remove the entire corrosion protection coating beneath the polymer
coating. Other top coat removal methods may be applied if they are shown to be of equal or
greater effectiveness.
Since Cr(VI) is toxic to human beings, all potential Cr(VI)-containing samples and reagents
used in the method shall be handled with appropriate precautions. Solutions or waste material
containing Cr(VI) shall be disposed of properly. For example, ascorbic acid or other reducing
agents can be used to reduce Cr(VI) to Cr(III) prior to disposal.
7 Boiling water extraction procedure
The boiling water extraction procedure is as follows:
a) Prepare the test solution as follows: dissolve 0,5 g of diphenylcarbazide (4.2 a)) in 50 ml
of acetone (4.2 d)). Dilute slowly, while stirring, with 50 ml of water (4.2 f)) (rapid mixing
may result in precipitation of diphenylcarbazide). For maximum stability, store this test
solution under refrigeration at 7 °C ± 2 °C in an amber glass bottle. Discard when the
solution becomes discoloured.
2 2
b) The sample to be tested should have a surface area of 50 cm ± 5 cm . For fasteners or
samples with smaller surface area, use a suitable number of samples to obtain the total
2 2
required surface area. In cases where obtaining a total surface area of 50 cm ± 5 cm is

not possible, a reduced total sample surface area may be used by reducing the water
extraction volume, while maintaining the same surface area to extraction volume ratio
2 2
(1 cm :1 ml). A minimum surface area of 25 cm is recommended. Similarly, a higher
sample surface area can be used by keeping the same ratio. The type of adjustment shall
be recorded in the final report.
The surface area of complex geometry samples can be estimated according to its
manufacturing specifications (e.g. mechanical drawings) if available, or by using its
dimensions and shape. For example: a flat-headed countersunk screw may be considered
as one metal cylinder (the screw body) adjacent to one metal cone (the screw head), as
shown in Figure 1.
H H
h b
IEC
Figure 1 – Screw body and screw head measurements
Estimated surface area of the screw body:
S = 2π R H + π(R )  (1)
b b b b
where
S is the estimated surface area of the screw body;
b
R is the radius of the screw body;
b
H is the height of the screw body.
b
Estimated surface area of the screw head:
2 2 2
S =πR (H +R ) +πR (2)
h h h h h
where
S is the estimated surface area of the screw head;
h
R is the top radius of the screw head;
h
H is the height of the screw head.
h
Total estimated surface area of the screw:
S = S + S (3)
t h b
where
S is the total estimated surface area of the screw.
t
NOTE The German Fastener Association, Deutscher Schraubenverband E.V. (DSV), offers a surface area
program for fastener surface area calculation via the International Material Data System (IMDS). Limitations of
this tool are documented within the program and users shall ensure this tool is applicable to the sample of
interest.
c) Add boiling chips (5.2 d)) and 50 ml of water (4.2 f)) to a beaker with volume graduation
(5.2 g)). Bring the water (4.2 f)) to boiling temperature (5.2 b) and 5.2 h)) for at least 10
min to deoxygenate the water; maintain the water volume by covering the beaker (5.2 g))
with a watch glass (5.2 k)). After boiling for at least 10 min, totally immerse the sample
into the boiling water. Cover the beaker (5.2 g)) with a watch glass (5.2 k)). Extract the
sample for 10 min ± 0,5 min once boiling is resumed. If necessary, add water (4.2 f)) to
ensure sample is totally submerged during the extraction. Remove the sample and allow
the resulting solution to cool to ambient temperature. The solution should be colourless
R
h
R
b
– 10 – IEC 62321-7-1:2015 © IEC 2015
and free of precipitate. Adjust the volume to 50 ml. If the solution is milky or has a
precipitate, filter the solution through a membrane filter (5.2 i)) into a dry beaker (5.2 g))
and adjust the volume back to 50 ml.
d) Add 1 ml of orthophosphoric acid solution (4.2 e)) and mix well. Pour 25 ml of the solution
using a graduated cylinder (5.2 e)) into another dry beaker (5.2 g)). Add 1 ml test solution
(7 a)), mix, and observe the colour. After a 10 min reaction time, a red to violet colour
indicates the presence of Cr(VI). The remaining portion of the extract will serve as the
blank.
e) If there is a colour interference (e.g. from a coating dye), a correction against the blank
shall be performed. Transfer a portion of the sample solution to an absorption cell (5.2 c)).
Measure the absorbance at 540 nm against the blank (7 d)) with the colorimetric
instrument (5.2 c)). Make three measurements and take the average as the final
absorbance of the sample. In some cases, depending on the type of spectrometer used,
the correction for the blank may have to be made manually in the collected data.
f) Place 50 ml of the 0,10 µg/cm equivalent comparison standard solution (4.2 c)) in a
beaker (5.2 g)). Add 1 ml of orthophosphoric acid solution (4.2 e)) and mix well. Add 2 ml
test solution (7 a)), mix, and wait 10 min for colour development. Measure the absorbance
three times as above. Take the average of three measurements as the final absorbance of
the standard solution.
g) Place 50 ml of the 0,13 µg/cm equivalent comparison standard solution (4.2 c)) in a
suitable beaker (5.2 g)). Add 1 ml of orthophosphoric acid solution (4.2 e)) and mix well.
Add 2 ml test solution (7 a)), mix, and wait 10 min for colour development. Measure the
absorbance three times as above. Take the average of three measurements as the final
absorbance of the standard solution.
h) If the absorbance value obtained in 7 d) or 7 e) is less than absorbance of the
0,10 µg/cm equivalent comparison standard solution (4.2 c)) obtained in 7 f), the sample
is considered to be negative for Cr(VI) (see Table 1).
i) If the absorbance value obtained in 7 d) or 7 e) is in between the values of the
2 2
0,10 µg/cm and 0,13 µg/cm equivalent comparison standard solutions (4.2 c)) obtained
in 7 f) and 7 g), the sample is in the “grey zone” where the presence or absence of Cr(VI)
in the sample is inconclusive (see Table 1).
j) If the absorbance value obtained in 7 d) or 7 e) is greater than the absorbance value of
the 0,13 µg/cm equivalent comparison standard solution (4.2 c)) obtained in 7 g), the
sample is considered to be positive for Cr(VI) (see Table 1).
In the case where the sample colour after the colorimetric reaction is significantly more
intense than the 0,13 µg/cm equivalent comparison standard such that the result can clearly
be determined as positive for Cr(VI), measurement via a colorimetric instrument is not
necessary. However, the report shall clearly state that the result is significantly above
0,13 µg/cm based on visual observation and no colorimetric measurement was performed.
Colorimetric measurement shall be performed if the Cr(VI) is not clearly above 0,13 µg/cm .

Table 1 – Comparison to standard solution and interpretation of results
Colorimetric result Qualitative result
(Cr(VI) concentration)
The sample solution is ˂ the 0,10 µg/cm equivalent The sample is negative for Cr(VI) − The Cr(VI)
comparison standard solution concentration is below the limit of quantification. The
coating is considered a non-Cr(VI) based coating
The sample solution is ≥ the 0,10 µg/cm and ≤ the The result is considered to be inconclusive –
Unavoidable coating variations may influence the
0,13 µg/cm equivalent comparison standard solutions
determination.
Recommendation: if addition samples are available,
perform a total of 3 trials to increase sampling surface
area. Use the averaged result of the 3 trials for the
final determination.
The sample solution is ˃ the 0,13 µg/cm equivalent The sample is positive for Cr(VI) − The Cr(VI)
comparison standard solution concentration is above the limit of quantification and
the statistical margin of error. The sample coating is
considered to contain Cr(VI)
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 manufacture 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 Traditional colorimetric instrument calibration shall be conducted using a blank and
three standard solutions at a minimum. The standard solution concentrations shall bracket the
two equivalent comparison standard solution concentrations (0,10 µg/ml and 0,13 µg/ml).
8.2.2 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.
8.2.3 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.
8.2.4 The calibration curve (linear fit with zero intercept) shall have a correlation coefficient
≥ 0,995 or a new curve shall be built.
8.2.5 Calibration curves can be used for up to one month from initial generation.
9 Calculation
The concentration of Cr(VI) shall be calculated according to Equation (4):
(C −B)×V
C(VI) = ×DF (4)
A
where
C(VI) is the sample coating concentration of chromium (VI) (µg/cm );

– 12 – IEC 62321-7-1:2015 © IEC 2015
C  is the sample solution concentration of chromium (VI) reading (µg/ml);
B is the concentration of reagent blank for sample preparation (µg/ml);
V is the volume of extract (ml);
A is the sample surface area (cm );
DF is the dilution factor (if no dilution is made, DF = 1).
10 Precision
Since the qualitative nature of this method does not lend itself to quantitative repeatability and
reproducibility statements (see ISO 78-2:1999, Annex B), the precision statements below
have been gleaned from 111/320/INF [1] .
• Seven laboratories submitted triplicate results and one laboratory submitted duplicate
results collected from a metal plate coated with hexavalent chromium (IIS4B-A1). All 23
results were positive for the presence of hexavalent chromium (˃ 0,13 µg/cm ).
• Eight laboratories submitted triplicate results collected from a metal screw coated with
hexavalent chromium (IIS4B-D4). All 24 results were positive for the presence of
hexavalent chromium (˃ 0,13 µg/cm ).
• Eight laboratories submitted triplicate results collected from a metal plate coated with
trivalent chromium (IIS4B-B2). Twenty (20) results were negative for the presence of
hexavalent chromium (< 0,10 µg/cm ), 3 results were inconclusive for the presence of
2 2
hexavalent chromium (≥ 0,10 µg/ cm and ≤ 0,13 µg/cm ) and one result was positive for
the presence of hexavalent chromium (˃ 0,13 µg/cm ).
• Eight laboratories submitted triplicate results collected from a metal screw coated with
trivalent chromium (IIS4B-E5). All 24 results were negative for the presence of hexavalent
chromium (< 0,10 µg/cm ).
• Eight laboratories submitted triplicate results collected from a metal plate coated without
any chromium (IIS4B-C3). All 24 results were negative for the presence of hexavalent
chromium (< 0,10 µg/cm ). See Annex A for supporting data.
11 Quality assurance and control
11.1 Colorimetric instrument performance verification
11.1.1 Regardless of the instrument type, a performance verification using the two
equivalent comparison standard solutions shall be carried out prior to sample measurements
and at the end of each sample sequence to ensure the instrument is functioning properly.
11.1.2 In the event that either of the equivalent comparison standard solutions measured
prior to sample measurements result in concentrations that differ from the expected values
(0,10 µg/ml and 0,13 µg/ml) by more than 15 %, the calibration shall be re-measured.
11.1.3 In the event that either of the equivalent comparison standard solutions measured at
the end of instrumental sequence result in concentrations that differ from the expected values
by more than 15 %, the calibration and all of the samples in the sequence shall be re-
measured.
11.2 Limits of detection (LOD) and limits of quantification (LOQ)
In its simplest form, a limit of detection (LOD) or method detection limit (MDL) is typically
described as the lowest amount or concentration of analyte in a test sample that can be
reliably differentiated from zero for a given measurement system.
______________
Numbers in square brackets refer to the Bibliography

Instrument detection limits represent an instrument’s ability to differentiate low concentrations
of analytes from “zero” in a blank or standard solution, and are commonly used by
manufacturers to demonstrate the measurement capability of a system (e.g. atomic absorption
spectrometer). While instrument detection limits are useful, they are often considerably lower
than a limit of detection representing a complete analytical method measurement process.
Complete analytical method detection limits are most appropriately determined experimentally
by performing replicate, independent measurements on low-level or fortified sample matrices
carried out through the entire test procedure, including sample digestion or extraction. A
minimum of six replicates and analyte concentrations of 3 to 5 times the estimated method
detection limit have been suggested as suitable for this analysis. The complete method
detection limit for an entire test procedure is determined by multiplying the standard deviation
of the replicates by an appropriate factor. The International Union of Pure and Applied

Chemistry (IUPAC) recommends a factor of 3 for a minimum of six replicates, while the United
States Environmental Protection Agency (US EPA) utilizes a one-sided confidence interval
with the multiplier equal to Student’s t value chosen for the number of replicates and the level
of confidence (e.g. t = 3,36 for six replicates for 99 % confidence).
All analyses used to calculate an MDL should be consecutive. The LOD or MDL was
determined using the appropriate Student’s t values and t-statistic shown in Table 2.
Table 2 – Student’s t values used for calculation of method detection limit
(LOD or MDL = t-statistic × standard deviation (sn-1))
Student’s t-statistic
Number of samples
(99 % confidence)
6 3,36
7 3,14
8 3,00
9 2,90
10 2,82
The limit of quantification (LOQ) or estimated quantification limit for a given measurement
system is typically described as the lowest concentration that can be reliably determined
within specified or acceptable limits of precision during routine laboratory operating conditions.
The acceptable precision limit is often defined as 10 % relative standard deviation or simply
expressed as a fixed multiple (2 to 10) of the method detection limit.
12 Test report
Clause 12 specifies which information is to be included in the test report and shall require
information on at least the following aspects of the test:
a) the sample;
b) the International Standard used (including its year of publication);
c) the method used (if the standard includes several);
d) the limit of detection (LOD) or limit of quantification (LOQ);
e) any deviations from the procedure (e.g. surface area, extract volume, etc.);
f) any unusual features observed;
g) the date of the test;
h) the numeric result(s) in 2 significant figures, following the format laid out in Table 3 and
the text within Table 3 that correspond to the numeric result(s).

– 14 – IEC 62321-7-1:2015 © IEC 2015
Visual comparison is only allowed in the case of a positive Cr(VI) determination. Otherwise,
the numeric result (in µg/cm ) shall be stated in the report.
Table 3 – Reporting table
Colorimetric results
Sample Cr(VI)
Sample identification (in mass per surface Results
concentration is:
area, µg/cm )
Sample name Numeric result obtained The sample is negative for
˂ 0,10 µg/cm
from colorimetric Cr(VI) − The Cr(VI)
measurement and concentration is below the
Equation (4)
limit of quantification. The
coating is considered a
non-Cr(VI) based coating.
Or
The result is considered to
≥ 0,10 µg/cm and
be inconclusive –
≤ 0,13 µg/cm
unavoidable coating
variations may influence
the determination.
Recommendation: if
addition samples are
available, perform a total
of 3 trials to increase
sampling surface area, use
the averaged result of the
3 trials for the final
determination.
Or
The sample is positive for
˃ 0,13 µg/cm
Cr(VI) − The Cr(VI)
concentration is above the
limit of quantification and
the statistical margin of
error. The sample coating
is considered to contain
Cr(VI).
Or
Sample name Sample solution is ˃ 0,13 µg/cm The sample is positive for
significantly more intense Cr(VI) based on visual
comparison only. No
than the 0,13 µg/cm
colorimetric measurement
equivalent comparison
was performed. (Visual
standard
comparison is allowed only
in the case of a positive
Cr(VI) determination, and
the actual value in µg/cm
is not required).
Table 4 shows examples of reporting with test results:
Sample N° 1: 0,060 µg/cm
Sample N° 2: 0,19 µg/cm
Sample N° 3: 0,11 µg/cm
Sam
...