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1、 Reference number ISO 17240:2004(E) ISO 2004 INTERNATIONAL STANDARD ISO 17240 First edition 2004-10-01 Fruit and vegetable products Determination of tin content Method using flame atomic absorption spectrometry Produits drivs des fruits et lgumes Dtermination de la teneur en tain Mthode par spectrom
2、trie dabsorption atomique avec flamme Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/24/2007 19:52:17 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 17240
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6、w. ISO 2004 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 ISOs member body i
7、n 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 copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2004 All rights reserved Copyright International Organization for Standardization Provided by IH
8、S under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/24/2007 19:52:17 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 17240:2004(E) ISO 2004 All rights reserved iii Foreword ISO (the International Organization for Standardization) i
9、s 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 represe
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11、rafted 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
12、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 17240 was prepar
13、ed by Technical Committee ISO/TC 34, Food products, Subcommittee SC 3, Fruit and vegetable products. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/24/2007 19:52:17 MDTNo reproduction o
14、r networking permitted without license from IHS -,-,- Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/24/2007 19:52:17 MDTNo reproduction or networking permitted without license from IHS
15、 -,-,- INTERNATIONAL STANDARD ISO 17240:2004(E) ISO 2004 All rights reserved 1 Fruit and vegetable products Determination of tin content Method using flame atomic absorption spectrometry 1 Scope This International Standard specifies an atomic absorption spectrometric method for the determination of
16、the tin content of fruit and vegetable products in the concentration range 10 mg/kg to 500 mg/kg. It is a rapid method, especially suitable for routine determinations of tin in canned fruits and vegetables contaminated with tin which has migrated from the can. The method can be applied with the pres
17、cribed amount of sample to products with a maximum total dry matter content of 30 %. Products with higher contents of total solids can be analysed using smaller amounts of sample after corresponding dilution with deionized water. NOTE The method of tin determination in fruit and vegetables products
18、is based on NMKL method No 126/1988 (reference 1 in Annex A). 2 Principle Fruit and vegetable products are digested in hydrochloric acid at 80 C and the tin content is determined by flame atomic absorption spectrometry. 3 Reagents Use only reagents of recognized analytical grade, unless otherwise sp
19、ecified, and deionized water or water of equivalent purity. 3.1 Hydrochloric acid, concentrated (20 = 1,19 g/ml). 3.2 Hydrochloric acid, dilute (c = 6 mol/l). Dilute 50 ml of hydrochloric acid (3.1) with water to 100 ml. 3.3 Tin, standard solution corresponding to 1,0 mg of tin per millilitre. 4 App
20、aratus 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 Block thermostat, or other device for rapid heating and temperature control. The required temperature accuracy is 3 C. 4
21、.3 Atomic absorption spectrometer, provided with a nitrous oxide/acetylene burner (5 cm), suitable for measurements at a wavelength of 235,5 nm. 4.4 Tin lamp, hollow cathode lamp or electrodeless discharge lamp (EDL). Copyright International Organization for Standardization Provided by IHS under lic
22、ense with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/24/2007 19:52:17 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 17240:2004(E) 2 ISO 2004 All rights reserved NOTE The detection limit of the method is significantly lower when EDL lamps are
23、 used. 4.5 Filter paper, Schleicher and Schull 589/1 (Black band)1) or equivalent. 4.6 Analytical balance. 5 Sample A representative sample should have been sent to the laboratory. It should not have been damaged or changed during transport or storage. 6 Procedure 6.1 Preparation of test sample Thor
24、oughly mix 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 pro
25、duct before mixing. 6.2 Test portion Weigh, to the nearest 0,001 g, 5 g of the test sample (6.1) into a glass tube suitable for the block thermostat (4.2) or directly into a 50 ml volumetric flask. 6.3 Decomposition Add 10 ml of dilute hydrochloric acid (3.2). Incubate the sample for 60 min in a blo
26、ck thermostat or in a water bath preheated to 80 C 3 C. Stir the mixture three or four times during the heating period. Transfer the sample quantitatively to a 50 ml volumetric flask and, after cooling, dilute to volume with water. Filter the sample through filter paper (4.5). The filtrate is now re
27、ady for measurement by atomic absorption spectrometry. Perform the determination preferably within 5 h to 6 h, or alternatively store the extract in a sealed plastic flask. 6.4 Blank test Carry out a blank test by transferring 10 ml of dilute hydrochloric acid (3.2) into a glass tube or a volumetric
28、 flask and use the same decomposition procedure (6.3) as for the test portion (6.2). 6.5 Determination 6.5.1 Preparation of the calibration graph Dilute the standard tin solution (3.3) adding 10 ml of concentrated hydrochloric acid (3.1) per 100 ml, to obtain an appropriate number of standard soluti
29、ons in the range 3,0 mg/l to 200 mg/l, when using a hollow cathode lamp, and in the range 1,0 mg/l to 200 mg/l, when using an EDL lamp. 1) Schleicher and Schull 589/ (Black Band) is an example of a suitable product available commercially. This information is only given for the convenience of users o
30、f this International Standard and does not constitute an endorsement by ISO of this product. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/24/2007 19:52:17 MDTNo reproduction or networ
31、king permitted without license from IHS -,-,- ISO 17240:2004(E) ISO 2004 All rights reserved 3 Ignite the nitrous oxide/acethylene flame of the atomic absorption spectrometer (4.3) according to the instrument instructions and adjust the gas flow to give a 2 cm red band above the burner head. Aspirat
32、e each of these solutions, in turn, into the flame of the spectrometer (4.3). Use a mixture of dilute hydrochloric acid with water (1 + 9) as a blank. Record the corresponding values of absorbance and plot the calibration graph (absorbance against tin concentration in milligrams per litre). 6.5.2 Sp
33、ectrometric measurement Set the instrument to the previously established optimum conditions, using the nitrous oxide/acethylene flame and a 235,5 nm resonant wavelength. Aspirate the test solution (6.3) and the blank solution (6.4) into the flame of the spectrometer (4.3). Record the corresponding a
34、bsorbances. 7 Calculation The tin content of the sample, w, expressed in milligrams per kilogram of the product, is given by the equation: b ()50 w m = where is the tin concentration of the test solution, expressed in milligrams per litre, read from the calibration graph; b is the tin concentration
35、of the blank test solution, expressed in milligrams per litre, read from the calibration graph; m is the mass, in grams, of the test portion. 8 Precision 8.1 General The precision of the method has been checked by collaborative studies (13 laboratories) of tin determinations in two samples of tomato
36、 soup and two samples of apple sauce (Reference 1 in Annex A). Statistical parameters are expressed according to ISO 5725-2 (Reference 2 in Annex A). 8.2 Repeatability 8.2.1 Tomato soup Sample 1: the repeatability coefficient of variation is 4,3 %. Sample 2: the repeatability coefficient of variatio
37、n is 2,4 %. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/24/2007 19:52:17 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 17240:2004(E) 4 ISO 2004 All ri
38、ghts reserved 8.2.2 Apple sauce Sample 1: the repeatability coefficient of variation is 1,078. Sample 2: the repeatability coefficient of variation is 0,406. NOTE The coefficient is dependent on the content of tin in the sample, and decreases with increasing tin content. 8.3 Reproducibility 8.3.1 To
39、mato soup Sample 1: the reproducibility coefficient of variation is 12,0 %. Sample 2: the reproducibility coefficient of variation is 7,1 %. 8.3.2 Apple sauce Sample 1: the reproducibility coefficient of variation is 9,4 %. Sample 2: the reproducibility coefficient of variation is 4,0 %. NOTE The co
40、efficient is dependent on the content of tin in the sample, and decreases with increasing tin content. 9 Test report The test report shall specify: a) all information necessary for the complete identification of the sample; b) the sampling method used; c) the test method used, with reference to this
41、 International Standard; d) all operating details not specified in this International Standard, or regarded as optional, together with details of any incidents which may have influenced the test result(s); e) the test result(s) obtained, or, if the repeatability has been checked, the final quoted re
42、sult obtained. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/24/2007 19:52:17 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 17240:2004(E) ISO 2004 All r
43、ights reserved 5 Bibliography 1 Nordic Committee on Food Analysis. No 126/1988. Tin. Determination by atomic absorption in fruits and vegetables 2 ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results Part 2: Basic method for the determination of repeatability and rep
44、roducibility of a standard measurement method Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/24/2007 19:52:17 MDTNo reproduction or networking permitted without license from IHS -,-,- I
45、SO 17240:2004(E) ICS 67.080.01 Price based on 5 pages ISO 2004 All rights reserved Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/24/2007 19:52:17 MDTNo reproduction or networking permitted without license from IHS -,-,-