1、BS ISO11813:2010ICS 67.100.01NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDMilk and milk products Determination ofzinc content Flameatomic absorptionspectrometric methodThis British Standardwas published under theauthority of the StandardsPolicy and StrategyCo
2、mmittee on 30 June2010 BSI 2010ISBN 978 0 580 70100 9Amendments/corrigenda issued since publicationDate CommentsBS ISO 11813:2010National forewordThis British Standard is the UK implementation of ISO 11813:2010. Itsupersedes BS ISO 11813:1998 which is withdrawn.The UK participation in its preparatio
3、n was entrusted to TechnicalCommittee AW/5, Chemical analysis of milk and milk products.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for i
4、ts correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.BS ISO 11813:2010Reference numbersISO 11813:2010(E)IDF 156:2010(E)ISO and IDF 2010INTERNATIONAL STANDARD ISO11813IDF156Second edition2010-06-01Milk and milk products Determination of zinc content F
5、lame atomic absorption spectrometric method Lait et produits laitiers Dtermination de la teneur en zinc Mthode par spectromtrie dabsorption atomique avec flamme BS ISO 11813:2010ISO 11813:2010(E) IDF 156:2010(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes l
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9、2010 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 or IDF at the respective address below. ISO copyr
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11、-idf.org Published in Switzerland ii ISO and IDF 2010 All rights reservedBS ISO 11813:2010ISO 11813:2010(E) IDF 156:2010(E) ISO and IDF 2010 All rights reserved iiiForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bod
12、ies). 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
13、 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,
14、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 cast
15、ing 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 11813IDF 156 was prepared by Technical Committee ISO/TC 34, Food products, Subcommitt
16、ee SC 5, Milk and milk products, and the International Dairy Federation (IDF). It is being published jointly by ISO and IDF. This second edition of ISO 11813IDF 156 cancels and replaces the first edition (ISO 11813:1998), of which it constitutes a minor revision. BS ISO 11813:2010ISO 11813:2010(E) I
17、DF 156:2010(E) iv ISO and IDF 2010 All rights reservedForeword IDF (the International Dairy Federation) is a non-profit organization representing the dairy sector worldwide. IDF membership comprises National Committees in every member country as well as regional dairy associations having signed a fo
18、rmal agreement on cooperation with IDF. All members of IDF have the right to be represented on the IDF Standing Committees carrying out the technical work. IDF collaborates with ISO in the development of standard methods of analysis and sampling for milk and milk products. The main task of Standing
19、Committees is to prepare International Standards. Draft International Standards adopted by the Standing Committees are circulated to the National Committees for endorsement prior to publication as an International Standard. Publication as an International Standard requires approval by at least 50% o
20、f IDF National Committees casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. IDF shall not be held responsible for identifying any or all such patent rights. ISO 11813IDF 156 was prepared by the International Dairy Fe
21、deration (IDF) and Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products. It is being published jointly by IDF and ISO. All work was carried out by the former Joint ISO-IDF Action Team on Minor compounds, now part of the Standing Committee on Analytical methods for
22、composition. This edition of ISO 11813IDF 156 cancels and replaces IDF 156:1992, of which it constitutes a minor revision. BS ISO 11813:2010INTERNATIONAL STANDARD ISO 11813:2010(E)IDF 156:2010(E) ISO and IDF 2010 All rights reserved 1Milk and milk products Determination of zinc content Flame atomic
23、absorption spectrometric method 1 Scope This International Standard specifies a flame atomic absorption spectrometric method for the determination of the zinc content of milk and milk products. The method has been validated for zinc contents of between 25 mg/kg and 70 mg/kg (dry mass) in milk and mi
24、lk products. 2 Normative references The following referenced documents are indispensable for the application 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 6732IDF 1
25、03, Milk and milk products Determination of iron content Spectrometric method (Reference method) 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 zinc content in milk and milk products mass fraction of substances determined by the procedure sp
26、ecified in this International Standard NOTE The zinc content is expressed in milligrams per kilogram of product. 4 Principle The sample is dry ashed in a programmable ashing furnace. The ash is dissolved in concentrated hydrochloric acid and, after adding strontium chloride solution, diluted with wa
27、ter. The zinc content of the resulting solution is measured by flame atomic absorption spectrometry at a wavelength of 213,9 nm with deuterium or Zeeman background correction. 5 Reagents Use only reagents of recognized analytical grade which, with the exception of the standard zinc solutions (5.5),
28、shall be free from zinc. BS ISO 11813:2010ISO 11813:2010(E) IDF 156:2010(E) 2 ISO and IDF 2010 All rights reservedUnless otherwise indicated, the use of Aristar, Suprapur or Ultrex reagents1)or products of equivalent reagent grade purity is strongly recommended. 5.1 Water, complying with grade 2 as
29、defined in ISO 36963. 5.2 Hydrochloric acid (HCl), concentrated (20= 1,17 g/ml to 1,18 g/ml). 5.3 Strontium chloride solution. Dissolve 38,0 g of strontium chloride hexahydrate (SrCl26H2O) in water (5.1) and make up to 250 ml with water. NOTE Strontium chloride hexahydrate from BDH (Spectrosol)1)or
30、equivalent is suitable. 5.4 Nitric acid (HNO3), concentrated (r20= 1,42 g/ml). 5.5 Zinc standard solutions. 5.5.1 Stock solution, containing 1 000 mg of zinc per litre of 0,3 mol/l nitric acid (equivalent to 18,9 g/l of nitric acid). NOTE Baker Instra-analyzed Atomic Spectral Solution1)1.6946 is sui
31、table. 5.5.2 Working solution, containing 100 mg of zinc per litre. Add 1 ml of nitric acid (5.4) to 10 ml of the stock solution (5.5.1) and make up to 100 ml with water (5.1). 5.6 Zero-standard solution. In a 500 ml one-mark volumetric flask, dilute 2,5 ml of hydrochloric acid (5.2) and 12,5 ml of
32、strontium chloride solution (5.3) with water (5.1) to the 500 ml mark. Mix well. 6 Apparatus IMPORTANT Store clean glassware in nitric acid, 10 % mass fraction. Rinse it three times before use with distilled water and then three times with double-distilled water. Usual laboratory equipment and in pa
33、rticular the following. 6.1 Quartz crucibles, with quartz lids, capacity 50 ml. 6.2 One-mark volumetric flasks, capacities 100 ml and 250 ml, ISO 10422class A. 6.3 Manual piston pipettes, capacities 0,2 ml, 1,0 ml, and 5,0 ml, ISO 8655-26. 6.4 Drying oven, capable of being maintained at 102 C 5 C. 6
34、.5 Programmable ashing furnace, or equivalent, capable of maintaining a minimum attainable temperature of 550 C with a heating rate programmable at 50 C/h. NOTE If a programmable ashing furnace is not available, manual adjustment of temperature of an isothermal furnace is possible in steps of 50 C e
35、very hour. 1) Aristar, Suprapur, Ultrex and Spectrosol reagents and Baker Instra-analyzed Atomic Spectral Solution are examples of suitable products available commercially. This information is given for the convenience of users of this International Standard and does not constitute an endorsement by
36、 ISO or IDF of these products. BS ISO 11813:2010ISO 11813:2010(E) IDF 156:2010(E) ISO and IDF 2010 All rights reserved 36.6 Hotplate, capable of maintaining a temperature of about 100 C. 6.7 Water bath, capable of maintaining water at boiling point. 6.8 Flame atomic absorption spectrometer, capable
37、of measuring at a wavelength of 213,9 nm with a recommended spectral band width of 0,2 nm and a 10 cm single-slot acetylene-air burner and deuterium or Zeeman background correction. 6.9 Analytical balance, capable of being read to the nearest 1 mg. 7 Sampling Sampling is not part of the method speci
38、fied in this International Standard. A recommended sampling method is given in ISO 707|IDF 501. It is important that the laboratory receive a truly representative sample which has not been damaged or changed during transport or storage. Store the sample in such a way that deterioration and change in
39、 its composition are prevented. Precautions should be taken to avoid contamination of the sample by zinc. 8 Preparation of test sample Avoiding contamination by zinc, prepare the test sample according to ISO 6732IDF 103. 9 Procedure 9.1 General If it is required to check whether the repeatability li
40、mit (see 11.2) is met, carry out two single determinations in accordance with 9.2 to 9.4. 9.2 Test portion Weigh, to the nearest 1 mg, 5 g 1 g of the prepared test sample of milk (or an amount of the prepared test sample of a milk product equivalent to 0,5 g 0,1 g of dry mass) into a quartz crucible
41、 (6.1). Dry the contents carefully in the oven (6.4) maintained at 102 C. 9.3 Ashing Heat the quartz crucible containing the dried test portion (9.2) in the ashing furnace (6.5) from room temperature to 500 C at a rate of 50 C/h. Maintain it for 3 h at a temperature of 500 C. Subsequently, let the c
42、ontents of the crucible cool to ambient temperature in a zinc-free cabinet. If no white ash is obtained, wet the ash with approximately 0,5 ml of water (5.1), then add three drops of nitric acid (5.4). Dry carefully on a hotplate (6.6) or on a boiling water bath (6.7). Heat again for 30 min in the f
43、urnace (6.5) maintained at 500 C. BS ISO 11813:2010ISO 11813:2010(E) IDF 156:2010(E) 4 ISO and IDF 2010 All rights reserved9.4 Determination 9.4.1 Preparation of test solution Add 0,5 ml of water (5.1) and 0,5 ml of hydrochloric acid (5.2) to the ash (9.3). Dissolve the ash and quantitatively transf
44、er the dissolved ash with water to a 100 ml one-mark volumetric flask (6.2). Using a 5,0 ml piston pipette (6.3), add 2,5 ml of strontium chloride solution (5.3) to the contents of the flask. Make up to the mark with water and mix thoroughly. 9.4.2 Atomic absorption spectrometric measurement Adjust
45、the spectrometer (6.8) to a wavelength of 213,9 nm and the flame conditions to yield optimum precision and sensitivity. 9.4.2.1 Calibration Add to four 100 ml one-mark volumetric flasks (6.2) 0,2 ml, 0,4 ml, 0,6 ml and 0,8 ml, respectively, of the zinc working solution (5.5.2). Make up to the mark w
46、ith the zero-standard solution (5.6) and mix thoroughly. These calibration solutions contain 0,2 mg, 0,4 mg, 0,6 mg and 0,8 mg of zinc per litre respectively. Subsequently, aspirate the zero-standard solution (5.6) and the four calibration solutions four times each and calculate the means of the abs
47、orbance values. Subtract from the means of the absorbance values of the calibration solutions the mean of the absorbance value of the zero-standard solution. Plot the resulting net absorbance values against the corresponding calibration concentrations. NOTE Depending on the functionalities of the in
48、strument, subtraction can also be done by autozeroing. 9.4.2.2 Measurement of sample solution Measure the test solution (see 9.4.1) immediately after the calibration measurements, under the same conditions. If its signal is above that of the highest standard, dilute the test solution with zero-stand
49、ard solution (5.6) (dilution factor f ) and repeat the measurements. Intermittently, check the instrument and the calibration stability by using the 0,4 mg/l zinc calibration solution. Also perform calibration measurements at the end of a series of measurements and, for large series, perform additional measurements in the middle of the series. Repeat each measurement four times and calculate the arithmetic average of these values. Subtract from it the mean absorbance value of the zero-standard s
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