1、BRITISH STANDARD BS ISO 17240:2004 Fruit and vegetable products Determination of tin content Method using flame atomic absorption spectrometry ICS 67.080.01 BS ISO 17240:2004 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 25 November 2004 BS
2、I 25 November 2004 ISBN 0 580 44871 1 National foreword This British Standard reproduces verbatim ISO 17240:2004 and implements it as the UK national standard. Any enquiries on this text should be forwarded to Head of International Content, Standards Development, BSI, 389 Chiswick High Road, London
3、W4 4AL, who will present to the responsible international/European committee any such enquiries on the interpretation, or proposals for change, and keep UK interests informed. Cross-references The British Standards which implement international publications referred to in this document may be found
4、in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are respons
5、ible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii and iii, a blank page, pages 1 to 5 and a back cover. The BSI co
6、pyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date Comments Reference number ISO 17240:2004(E) OSI 4002INTERNATIONAL STANDARD ISO 17240 First edition 2004-10-01 Fruit and vegetable products Determination of tin con
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12、+ 10 947 22 1 11 xaF0 947 22 14 + 9 74 E-mail coirypthgiso.o gr We bwww.is.o gro Pulbisdehi n Switlrez dnaii ISO 4002 Allr ithgsr esedevrBSISO17240:2004IS:04271 O4002(E) I SO 4002 All irthgs ersedevr iiiForeword ISO (the International Organization for Standardization) is a worldwide federation of na
13、tional 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. Intern
14、ational 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
15、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
16、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 prepared by Technical Committee ISO/
17、TC 34, Food products, Subcommittee SC 3, Fruit and vegetable products. BSISO17240:2004blank 4002:04271OSISBINTENRATIONAL TSANDADR IS:04271 O4002(E)I SO 4002 All irthgs ersedevr 1Fruit and vegetable products Determination of tin content Method using flame atomic absorption spectrometry 1 Scope This I
18、nternational Standard specifies an atomic absorption spectrometric method for the determination of 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 vegeta
19、bles contaminated with tin which has migrated from the can. The method can be applied with the prescribed 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 di
20、lution with deionized water. NOTE The method of tin determination in fruit and vegetables products 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 absorp
21、tion spectrometry. 3 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, 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) wi
22、th water to 100 ml. 3.3 Tin, standard solution corresponding to 1,0 mg of tin per millilitre. 4 Apparatus 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
23、other device for rapid heating and temperature control. The required temperature accuracy is 3 C. 4.3 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 disch
24、arge lamp (EDL). BSISO17240:2004IS:04271 O4002(E) 2 I SO 4002 All irthgs ersedevrNOTE The detection limit of the method is significantly lower when EDL lamps are used. 4.5 Filter paper, Schleicher and Schull 589/1 (Black band) 1)or equivalent. 4.6 Analytical balance. 5 Sample A representative sample
25、 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 Thoroughly mix the laboratory sample. If necessary, first remove any seeds, stalks and hard seed-cavity walls, and then grind in the mechanical
26、 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 0,001 g, 5 g of the test sample (6.1) into a glass tube suitable for the block t
27、hermostat (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 block 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
28、 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 ready for measurement by atomic absorption spectrometry. Perform the determination preferably within 5 h to 6 h, or alternatively store the e
29、xtract 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 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
30、 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 solutions 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)
31、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 of this International Standard and does not constitute an endorsement by ISO of this product. BSISO17240:2004IS:04271 O4002(E) I SO 4002 All
32、 irthgs ersedevr 3Ignite 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. Aspirate each of these solutions, in turn, into the flame of the spectrometer (4.3).
33、 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 Spectrometric measurement Set the instrument to the previously established opti
34、mum 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 absorbances. 7 Calculation The tin content of the sample, w, expressed in mill
35、igrams per kilogram of the product, is given by the equation: b () 5 0 w m = where is the tin concentration of the test solution, expressed in milligrams per litre, read from the calibration graph; bis the tin concentration of the blank test solution, expressed in milligrams per litre, read from the
36、 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 soup and two samples of apple sauce (Reference 1 in Annex A). Statistical p
37、arameters 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 variation is 2,4 %. BSISO17240:2004IS:04271 O4002(E) 4 I SO 4002 All irthgs ersedevr
38、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 Tomato soup Samp
39、le 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 coefficient is d
40、ependent 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 International
41、 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 result obtained.
42、 BSISO17240:2004IS:04271 O4002(E) I SO 4002 All irthgs ersedevr 5Bibliography 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 metho
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