Cereals -- Determination of cadmium content by graphite furnace atomic absorption spectrometry with diluted nitric acid extraction

This document specifies a method for the determination of cadmium (Cd) in cereals. It is applicable to rice, brown rice, wheat and maize by graphite furnace atomic absorption spectrometry (GFAAS) after extraction with diluted nitric acid (HNO3). The limit of quantification is 0,002Â mg/kg; it is approximate and dependent on the sample matrix as well as on the instrument conditions.

Céréales -- Détermination de la teneur en cadmium par spectrométrie d'absorption atomique en four graphite et extraction à l'aide d'acide nitrique dilué

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Published
Publication Date
14-Dec-2021
Current Stage
5060 - Close of voting Proof returned by Secretariat
Start Date
25-Nov-2021
Completion Date
24-Nov-2021
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ISO/FDIS 23637 - Cereals -- Determination of cadmium content by graphite furnace atomic absorption spectrometry with diluted nitric acid extraction
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FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 23637
ISO/TC 34/SC 4
Cereals — Determination of cadmium
Secretariat: SAC
content by graphite furnace atomic
Voting begins on:
2021-09-29 absorption spectrometry with diluted
nitric acid extraction
Voting terminates on:
2021-11-24
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 23637:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
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LIGHT OF THEIR POTENTIAL TO BECOME STAN-
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NATIONAL REGULATIONS. © ISO 2021
---------------------- Page: 1 ----------------------
ISO/FDIS 23637:2021(E)
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© ISO 2021 – All rights reserved
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ISO/FDIS 23637:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Reagents and solution ....................................................................................................................................................................................1

6 Apparatus and equipment ......................................................................................................................................................................... 2

7 Procedure ....................................................................................................................................................................................................................2

7.1 General ........................................................................................................................................................................................................... 2

7.2 Sampling ....................................................................................................................................................................................................... 2

7.3 Preparation of the test samples............................................................................................................................................... 3

7.4 Extraction ................................................................................................................................................................................................... 3

7.4.1 General ........................................................................................................................................................................................ 3

7.4.2 Reagent blank ........................................................................................................................................................................ 3

7.5 Sample analysis ........................................................................................................................................... ........................................... 3

7.5.1 General ........................................................................................................................................................................................ 3

7.5.2 Operating conditions ...................................................................................................................................................... 3

7.5.3 Calibration graph ............................................................................................................................................................... 3

7.5.4 Determination ...................................................................................................................................................................... 4

7.5.5 Application of matrix-modifier .............................................................................................................................. 4

7.6 Analytical quality control ............................................................................................................................................................. 4

8 Calculation .................................................................................................................................................................................................................. 4

9 Precision ....................................................................................................................................................................................................................... 4

9.1 General ........................................................................................................................................................................................................... 4

9.2 Repeatability ............................................................................................................................................................................................ 5

9.3 Reproducibility ....................................................................................................................................................................................... 5

9.4 Critical difference, D .......................................................................................................................................................................... 5

9.4.1 General ........................................................................................................................................................................................ 5

9.4.2 Comparison of two groups of measurements in one laboratory ............................................. 5

9.4.3 Comparison of two groups of measurements in two laboratories ........................................ 5

10 Test report .................................................................................................................................................................................................................. 6

Annex A (informative) Results of interlaboratory tests ................................................................................................................. 7

Bibliography .............................................................................................................................................................................................................................10

iii
© ISO 2021 – All rights reserved
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ISO/FDIS 23637:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

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For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 4,

Cereals and pulses.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
© ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 23637:2021(E)
Cereals — Determination of cadmium content by graphite
furnace atomic absorption spectrometry with diluted
nitric acid extraction
1 Scope

This document specifies a method for the determination of cadmium (Cd) in cereals.

It is applicable to rice, brown rice, wheat and maize by graphite furnace atomic absorption spectrometry

(GFAAS) after extraction with diluted nitric acid (HNO ). The limit of quantification is 0,002 mg/kg; it

is approximate and dependent on the sample matrix as well as on the instrument conditions.

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.

ISO 3696, Water for analytical laboratory use — Specification and test methods
3 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Principle

Cadmium (Cd) is extracted from the cereals using diluted nitric acid and then determined by graphite

furnace atomic absorption spectrometry (GFAAS).
5 Reagents and solution

During the analysis, unless otherwise stated, use only reagents of recognized analytical purity and only

water of grade 1 in accordance with ISO 3696.

5.1 Nitric acid (HNO ), not less than 65 % (mass fraction) of approximately ρ(HNO ) = 1,4 g/ml.

3 3

5.2 Nitric acid solution (0,5 %, volume fraction), mix 0,5 volume parts of HNO (5.1) and 100 ml

volume parts of water.

5.3 Nitric acid solution (50 %, volume fraction), mix HNO (5.1) and water in equal volume.

5.4 Palladium nitrate hydrate (Pd(NO ) , 99,9 % purity).
3 2
© ISO 2021 – All rights reserved
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ISO/FDIS 23637:2021(E)

5.5 Palladium nitrate (Pd(NO ) ) solution, c(Pd(NO ) ) = 100 mg/l, dissolve 0,1 g Pd(NO ) (5.4)

3 2 3 2 3 2

and dilute to 1 000 ml with HNO (5.2). Other matrix modifiers may also be used if their applicability is

proven.
5.6 Cadmium standard solution.

5.6.1 Cadmium stock standard solution, with a cadmium mass concentration of 1 000 mg/l or

500 mg/l.

5.6.2 Cadmium standard solution, stepwise dilute cadmium stock solution (5.6.1) into concentration

of 2 μg /l with HNO (5.2).

5.6.3 Cadmium calibration solutions, pipette suitable volumes of cadmium standard solution

(5.6.2), e.g. 2 ml, 4 ml, 6 ml, 8 ml and 10 ml, into, for example, a 10 ml volumetric flask (6.7) and dilute

to the mark with diluted nitric acid solution (5.2). The concentration of cadmium in the calibration

solutions should cover the range of 0,4 μg /l to 2,0 μg/l.
6 Apparatus and equipment

All glassware shall be cleaned several times with water after being soaked overnight with HNO (5.3)

and rinsed three times with ultrapure water before use.

6.1 Grinding mill, grinder suitable to obtain the particle sizes of 0,25 mm and 0,40 mm.

6.2 Atomic absorption spectrometer, equipped with graphite furnace, autosampler and background

correction capability, such as Zeeman background correction.

6.3 Cadmium hollow cathode lamp, with wavelength 228,8 nm and stable lamp energy.

6.4 Centrifuge, with positions for 10 ml centrifuge tubes and 3 000 r/min of speed.

6.5 Analytical balance, accurate to 1 mg.
6.6 Sieve, with aperture sizes of 0,25 mm and 0,40 mm.
6.7 Plastic centrifuge tube, 10 ml.
7 Procedure
7.1 General
The measurement should be performed as soon as possible after extraction.
7.2 Sampling
A representative sample should be sent to the laboratory. It should not h
...

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