ISO 2447:1998

INTERNATIONAL ISO
STANDARD 2447
Second edition
1998-08-01
Fruit and vegetable products —
Determination of tin content
Produits dérivés des fruits et légumes — Détermination de la teneur
en étain
A
Reference number
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.
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.
International Standard ISO 2447 was prepared by Technical Committee ISO/TC 34, Agricultural food products,
Subcommittee SC 3, Fruit and vegetable products.
This second edition cancels and replaces the first edition (ISO 2447:1974), which has been technically revised.
©  ISO 1998
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 the publisher.
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Printed in Switzerland
ii
INTERNATIONAL STANDARD  © ISO ISO 2447:1998(E)
Fruit and vegetable products — Determination of tin content
1 Scope
This International Standard specifies a method for the determination of the tin content in fruit and vegetable
products.
The method is applicable to products which may contain, per kilogram, up to:
 1,25 g of copper;
 0,6 g of lead;
 6 g of zinc;
 40 g of phosphorus.
2 Normative reference
The following standard contains provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the edition indicated was valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent edition of the standard indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
ISO 5515:1979, Fruits, vegetables and derived products — Decomposition of organic matter prior to analysis —
Wet method.
3 Principle
After destruction of the organic matter by means of sulfuric and nitric acids, and conversion of the tin to the stannic
form, a complex is formed in a buffered solution of pH 1,0 to pH 1,2 [the iron(III) being masked, if necessary, by
reduction with ascorbic acid]. The complex is coloured orange with phenylfluorone and the colour compared with
those obtained under the same conditions but starting from standard solutions of pure tin.
4 Reagents
Use only reagents of recognized analytical grade, and distilled or demineralized water or water of equivalent purity.
4.1  Sulfuric acid, r = 1,84 g/ml.
4.2  Dilute sulfuric acid, 1,25 mol/l.
4.3  Ascorbic acid, 50 g/l solution.
4.4  Nitric acid, r = 1,42 g/ml.
© ISO
4.5  Hydrochloric acid, r = 1,19 g/ml.
4.6  Methanol.
4.7  Ethanol, 95 % (V/V).
4.8  Poly(vinyl alcohol), 16 g/l solution.
Dissolve 1,6 g of poly(vinyl alcohol) in a little water with gentle warming and agitation. Dilute to 100 ml after cooling.
4.9  Buffer solution, containing 450 g of sodium acetate (CH COONa) and 240 ml of acetic acid (CH COOH) per
3 3
litre.
4.10  Tin, standard volumetric solution I, containing 500 μg/ml in a sulfuric acid medium, approximately 3 mol/l.
Dissolve, with heating, 0,5 g of pure tin in a mixture of 50 ml of sulfuric acid (4.1), 5 ml of nitric acid (4.4) and 25 ml
of water. After complete solution, oxidize the tin to the stannic form by boiling until white fumes appear.
Cool the solution and pour it into a 1 000 ml volumetric flask containing 116 ml of sulfuric acid (4.1) and 100 ml of
water. Cool and dilute to 1 000 ml with water.
NOTE Alternatively, the tin standard solution I (4.10) may be prepared by dilution of a suitable proprietary standard
solution.
4.11  Tin, standard volumetric solution II, containing 10 μg/ml in a sulfuric acid medium, approximately
0,25 mol/l.
Transfer 20 ml of the tin standard volumetric solution I (4.10) to a 1 000 ml volumetric flask. Add 10 ml of sulfuric
acid (4.1) and dilute to 1 000 ml with water.
4.12  Phenylfluorone reagent (2,6,7-trihydroxy-9-phenyl-3-isoxathone).
Dissolve 0,1 g of phenylfluorone in 10 ml of methanol (4.6) and 1 ml of hydrochloric acid (4.5) in a 500 ml volumetric
flask. Dilute to the mark with ethanol (4.7).
The
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