SIST ISO 6561-2:2011

Fruits, vegetables and derived products -- Determination of cadmium content -- Part 2: Method using flame atomic absorption spectrometry

ISO 6561-2:2005 specifies an atomic absorption spectrometric method for the determination of the cadmium content of fruits, vegetables and derived products.

Fruits, légumes et produits dérivés -- Détermination de la teneur en cadmium -- Partie 2: Méthode par spectrométrie d'absorption atomique avec flamme

Sadje, zelenjava in sadni ter zelenjavni proizvodi - Določevanje kadmija - 2. del: Metoda s plamensko atomsko absorpcijo

Ta del ISO 6561 določa spektrometrično metodo z atomsko absorpcijo za določevanje kadmija v sadju, zelenjavi in sadnih ter zelenjavnih proizvodih.
OPOMBA: Metoda določevanja kadmija v sadju, zelenjavi in sadnih ter zelenjavnih proizvodih temelji na Uradnih analitskih metodah AOAC [1].

General Information

• Status: Published
• Public Enquiry End Date: 19-May-2011
• Publication Date: 15-May-2011
• ICS: 67.080.01 - Fruits, vegetables and derived products in general
• Technical Committee: KŽP - Agricultural food products
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 06-May-2011
• Due Date: 11-Jul-2011
• Completion Date: 16-May-2011
• Ref Project: ISO 6561-2:2005 - Fruits, vegetables and derived products - Determination of cadmium content - Part 2: Method using flame atomic absorption spectrometry

Relations

• Replaces: SIST ISO 6561:1995 - Fruits, vegetables and derived products -- Determination of cadmium content -- Flameless atomic absorption spectrometric method
• Effective Date: 01-Jun-2011

Overview

ISO 6561-2:2005 specifies a validated laboratory method for the determination of cadmium content in fruits, vegetables and derived products using flame atomic absorption spectrometry (FAAS). This part of ISO 6561 complements ISO 6561-1 (graphite furnace AAS) and is based on AOAC procedures. The standard covers sample preparation, chemical reagents, instrumental settings, calculation and precision data required for reliable cadmium analysis.

Key topics and technical requirements

• Scope: Determination of cadmium in fruit and vegetable matrices and processed products by FAAS.
• Sample preparation: Representative laboratory sample grinding; typical test portion = 50 g. Frozen products must be thawed and included.
• Decomposition/digestion: Wet digestion of organic matrix using concentrated nitric acid (HNO3), followed by sulfuric acid (H2SO4) and controlled addition of hydrogen peroxide (H2O2) to obtain a colourless digest.
• Extraction chemistry: Complexation and solvent extraction of cadmium using dithizone in chloroform at pH ≈ 8.8 (adjusted with ammonia and monitored with thymol blue). Warning: chloroform is toxic and ozone-depleting - use a fume hood and follow waste-disposal rules.
• Instrumental conditions: FAAS with an air/acetylene burner (10 cm recommended) and measurement at 228.8 nm. Calibration uses cadmium standards (0.1, 0.5, 1.0 and 2.0 µg/ml) prepared in dilute HCl.
• Calibration and measurement: Prepare a calibration graph (absorbance vs µg/ml), measure sample and blank at the same aspiration rate, dilute samples exceeding the highest standard.
• Calculation: Cadmium concentration is derived from the calibration curve, corrected for blank, sample mass and dilution factor.
• Precision: Interlaboratory repeatability and reproducibility values provided from collaborative studies (examples: lettuce and potatoes at levels 0.05–1.5 mg/kg).

Applications and users

• Food testing laboratories analyzing cadmium residues in fresh produce and processed fruit/vegetable products.
• Regulatory agencies and quality control units enforcing maximum cadmium limits in food.
• Research groups studying heavy metal uptake, food safety risk assessment, and agronomy.
• Analysts choosing between FAAS (ISO 6561-2) and higher-sensitivity methods (ISO 6561-1 graphite furnace) depending on required detection limits.

Related standards

• ISO 6561-1: Method using graphite furnace AAS (for lower detection limits)
• AOAC Official Methods of Analysis (basis for procedure)
• ISO 5725 series (precision - repeatability and reproducibility principles)

Keywords: ISO 6561-2:2005, cadmium determination, fruits and vegetables, flame atomic absorption spectrometry, FAAS, dithizone extraction, sample digestion, calibration graph, repeatability, reproducibility.

Standards Content (Sample)

SLOVENSKI STANDARD
01-junij-2011
1DGRPHãþD
SIST ISO 6561:1995
6DGMH]HOHQMDYDLQVDGQLWHU]HOHQMDYQLSURL]YRGL'RORþHYDQMHNDGPLMDGHO
0HWRGDVSODPHQVNRDWRPVNRDEVRUSFLMR
Fruits, vegetables and derived products -- Determination of cadmium content -- Part 2:
Method using flame atomic absorption spectrometry
Fruits, légumes et produits dérivés -- Détermination de la teneur en cadmium -- Partie 2:
Méthode par spectrométrie d'absorption atomique avec flamme
Ta slovenski standard je istoveten z: ISO 6561-2:2005
ICS:
67.080.01 Sadje, zelenjava in njuni Fruits, vegetables and
proizvodi na splošno derived products in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL ISO
STANDARD 6561-2
First edition
2005-02-01
Fruits, vegetables and derived
products — Determination of cadmium
content —
Part 2:
Method using flame atomic absorption
spectrometry
Fruits, légumes et produits dérivés — Détermination de la teneur en
cadmium —
Partie 2: Méthode par spectrométrie d'absorption atomique avec
flamme
Reference number
©
ISO 2005
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO 2005
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2005 – All rights reserved

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 6561-2 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 3, Fruit and
vegetable products.
This first edition of ISO 6561-2, together with ISO 6561-1:2004, cancels and replaces ISO 6561:1983, which
has been technically revised.
ISO 6561 consists of the following parts, under the general title Fruits, vegetables and derived products —
Determination of cadmium content:
 Part 1: Method using graphite furnace atomic absorption spectrometry
 Part 2: Method using flame atomic absorption spectrometry
INTERNATIONAL STANDARD ISO 6561-2:2005(E)

Fruits, vegetables and derived products — Determination of
cadmium content —
Part 2:
Method using flame atomic absorption spectrometry
1 Scope
This part of ISO 6561 specifies an atomic absorption spectrometric method for the determination of the
cadmium content of fruits, vegetables and derived products.
NOTE The method of cadmium determination in fruit, vegetables and derived products is based on AOAC Official
[1]
Methods of Analysis .
2 Principle
This method is based on the decomposition of organic matter with HNO , H SO and H O , extraction of
3 2 4 2 2
cadmium by dithizone-CHCl at pH 9, and determination of cadmium by flame atomic absorption spectrometry.
3 Reagents
Use only reagents of recognized analytical grade, unless otherwise specified, and water which has been
distilled twice in borosilicate glass apparatus, or water of at least equivalent purity.
3.1 Nitric acid, concentrated (ρ = 1,38 g/ml).
3.2 Sulfuric acid, concentrated (ρ = 1,84 g/ml).
3.3 Hydrochloric acid, dilute, 0,2 mol/l.
Place 16,5 ml of concentrated hydrochloric acid (ρ = 1,19 g/ml) into a 1 000 ml one-mark volumetric flask
and dilute to the mark with water. Mix.
3.4 Hydrogen peroxide, concentrated (50 %).
3.5 Citric acid monohydrate.
3.6 Sodium hydroxide, 0,05 mol/l solution.
3.7 Thymol blue indicator.
Triturate 0,1 g of thymol blue indicator in an agate mortar with 4,3 ml of sodium hydroxide solution (3.6). Dilute
to 200 ml in a flask with water.
3.8 Ammonia solution, 28 % to 30 % solution.
3.9 Chloroform.
3.10 Dithizone, 1,0 mg/ml solution.
Place 0,2 g of dithizone in a 200 ml volumetric flask and add chloroform to the mark.
3.11 Dithizone, 0,2 mg/ml solution.
Dilute dithizone solution (3.10) 1 + 4 with chloroform (3.9). Prepare fresh daily.
3.12 Cadmium standard solution, corresponding to a cadmium concentration of 1,0 mg/ml.
4 Apparatus
Before use, wash all glassware with 8 mol/l nitric acid, followed by a thorough rinse with water.
Cover beakers with watch glasses during all operations.
Usual laboratory apparatus and, in particular, the following.
4.1 Mechanical grinder, the inside and the blades of which are coated with polytetrafluoroethylene (PTFE).
4.2 Round-bottom flasks, of 1 500 ml capacity.
4.3 Beaker, of 400 ml capacity.
4.4 One-mark volumetric flasks, of capacities 50 ml, 100 ml and 1 000 ml.
4.5 Pipettes, of appropriate capacity.
4.6 Separators, 125 ml and 250 ml capacities.
4.7 Atomic absorption spectrometer, provided with an air/acetylene burner (10 cm), suitable for
measurements at a wavelength of 228,8 nm.
4.8 Burner or heating mantle.
4.9 Hot plate.
4.10 Analytical balance.
5 Sampling
A representative sample should have been sent to the laboratory. It should not have been damaged or
changed during transport or storage.
Sampling is not part of the method specified in this part of ISO 6561. If there is no specific International
Standard dealing with the product concerned, it is recommended that the parties concerned come to an
agreement on the subject.
2 © ISO 2005 – All rights reserved

6 Procedure
6.1 Prepa
...

INTERNATIONAL ISO
STANDARD 6561-2
First edition
2005-02-01
Fruits, vegetables and derived
products — Determination of cadmium
content —
Part 2:
Method using flame atomic absorption
spectrometry
Fruits, légumes et produits dérivés — Détermination de la teneur en
cadmium —
Partie 2: Méthode par spectrométrie d'absorption atomique avec
flamme
Reference number
©
ISO 2005
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO 2005
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2005 – All rights reserved

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 6561-2 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 3, Fruit and
vegetable products.
This first edition of ISO 6561-2, together with ISO 6561-1:2004, cancels and replaces ISO 6561:1983, which
has been technically revised.
ISO 6561 consists of the following parts, under the general title Fruits, vegetables and derived products —
Determination of cadmium content:
 Part 1: Method using graphite furnace atomic absorption spectrometry
 Part 2: Method using flame atomic absorption spectrometry
INTERNATIONAL STANDARD ISO 6561-2:2005(E)

Fruits, vegetables and derived products — Determination of
cadmium content —
Part 2:
Method using flame atomic absorption spectrometry
1 Scope
This part of ISO 6561 specifies an atomic absorption spectrometric method for the determination of the
cadmium content of fruits, vegetables and derived products.
NOTE The method of cadmium determination in fruit, vegetables and derived products is based on AOAC Official
[1]
Methods of Analysis .
2 Principle
This method is based on the decomposition of organic matter with HNO , H SO and H O , extraction of
3 2 4 2 2
cadmium by dithizone-CHCl at pH 9, and determination of cadmium by flame atomic absorption spectrometry.
3 Reagents
Use only reagents of recognized analytical grade, unless otherwise specified, and water which has been
distilled twice in borosilicate glass apparatus, or water of at least equivalent purity.
3.1 Nitric acid, concentrated (ρ = 1,38 g/ml).
3.2 Sulfuric acid, concentrated (ρ = 1,84 g/ml).
3.3 Hydrochloric acid, dilute, 0,2 mol/l.
Place 16,5 ml of concentrated hydrochloric acid (ρ = 1,19 g/ml) into a 1 000 ml one-mark volumetric flask
and dilute to the mark with water. Mix.
3.4 Hydrogen peroxide, concentrated (50 %).
3.5 Citric acid monohydrate.
3.6 Sodium hydroxide, 0,05 mol/l solution.
3.7 Thymol blue indicator.
Triturate 0,1 g of thymol blue indicator in an agate mortar with 4,3 ml of sodium hydroxide solution (3.6). Dilute
to 200 ml in a flask with water.
3.8 Ammonia solution, 28 % to 30 % solution.
3.9 Chloroform.
3.10 Dithizone, 1,0 mg/ml solution.
Place 0,2 g of dithizone in a 200 ml volumetric flask and add chloroform to the mark.
3.11 Dithizone, 0,2 mg/ml solution.
Dilute dithizone solution (3.10) 1 + 4 with chloroform (3.9). Prepare fresh daily.
3.12 Cadmium standard solution, corresponding to a cadmium concentration of 1,0 mg/ml.
4 Apparatus
Before use, wash all glassware with 8 mol/l nitric acid, followed by a thorough rinse with water.
Cover beakers with watch glasses during all operations.
Usual laboratory apparatus and, in particular, the following.
4.1 Mechanical grinder, the inside and the blades of which are coated with polytetrafluoroethylene (PTFE).
4.2 Round-bottom flasks, of 1 500 ml capacity.
4.3 Beaker, of 400 ml capacity.
4.4 One-mark volumetric flasks, of capacities 50 ml, 100 ml and 1 000 ml.
4.5 Pipettes, of appropriate capacity.
4.6 Separators, 125 ml and 250 ml capacities.
4.7 Atomic absorption spectrometer, provided with an air/acetylene burner (10 cm), suitable for
measurements at a wavelength of 228,8 nm.
4.8 Burner or heating mantle.
4.9 Hot plate.
4.10 Analytical balance.
5 Sampling
A representative sample should have been sent to the laboratory. It should not have been damaged or
changed during transport or storage.
Sampling is not part of the method specified in this part of ISO 6561. If there is no specific International
Standard dealing with the product concerned, it is recommended that the parties concerned come to an
agreement on the subject.
2 © ISO 2005 – All rights reserved

6 Procedure
6.1 Preparation of test sample
Mix well the laboratory sample, if necessary, first remove any seeds, stalks and hard seed-cavity walls, and
then grind in the mechanical grinder (4.1).
Frozen or deep-frozen products shall be previously thawed in a closed vessel, and the liquid formed during
this process shall be added to the product before mixing.
6.2 Test portion
Weigh, to the nearest 0,01 g, 50 g of the test sample (6.1) into a 1 500 ml round-bottom flask (4.2).
6.3 Decomposition
If the test portion contains ethanol, first remove the ethanol by evaporation.
Add several boiling chips or beads and carefully add
...