BS ISO 12081-2010 Milk - Determination of calcium content - Titrimetric method《牛乳 钙含量的测定 滴定法》.pdf

1、BS ISO12081:2010ICS 67.100.10NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDMilk Determinationof calcium content Titrimetric methodThis British Standardwas published under theauthority of the StandardsPolicy and StrategyCommittee on 30 June2010 BSI 2010ISBN 978

2、 0 580 70101 6Amendments/corrigenda issued since publicationDate CommentsBS ISO 12081:2010National forewordThis British Standard is the UK implementation of ISO 12081:2010. Itsupersedes BS ISO 12081:1998 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee A

3、W/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 its correct application.Compliance with

4、a British Standard cannot confer immunityfrom legal obligations.BS ISO 12081:2010Reference numbersISO 12081:2010(E)IDF 36:2010(E)ISO and IDF 2010INTERNATIONAL STANDARD ISO12081IDF36Second edition2010-06-01Milk Determination of calcium content Titrimetric method Lait Dtermination de la teneur en calc

5、ium Mthode titrimtrique BS ISO 12081:2010ISO 12081:2010(E) IDF 36:2010(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and in

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8、kely event that a problem relating to it is found, please inform the ISO Central Secretariat at the address given below. COPYRIGHT PROTECTED DOCUMENT ISO and IDF 2010 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any mean

9、s, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO or IDF at the respective address below. ISO copyright office International Dairy Federation Case postale 56 CH-1211 Geneva 20 Diamant Building Boulevard Auguste Reyers 80 B-1030 Brussels

10、Tel. + 41 22 749 01 11 Tel. + 32 2 733 98 88 Fax + 41 22 749 09 47 Fax + 32 2 733 04 13 E-mail copyrightiso.org E-mail infofil-idf.org Web www.iso.org Web www.fil-idf.org Published in Switzerland ii ISO and IDF 2010 All rights reservedBS ISO 12081:2010ISO 12081:2010(E) IDF 36:2010(E) ISO and IDF 201

11、0 All rights reserved iiiForeword 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 i

12、n 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 Commis

13、sion (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

14、 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

15、 not be held responsible for identifying any or all such patent rights. ISO 12081IDF 36 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF). It is being published jointly by ISO and IDF. This second edi

16、tion of ISO 12081IDF 36 cancels and replaces the first edition (ISO 12081:1998), of which it constitutes a minor revision. BS ISO 12081:2010ISO 12081:2010(E) IDF 36:2010(E) iv ISO and IDF 2010 All rights reservedForeword IDF (the International Dairy Federation) is a non-profit organization represent

17、ing the dairy sector worldwide. IDF membership comprises National Committees in every member country as well as regional dairy associations having signed a formal agreement on cooperation with IDF. All members of IDF have the right to be represented on the IDF Standing Committees carrying out the te

18、chnical 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 Committees is to prepare International Standards. Draft International Standards adopted by the Standing Committees are circulated to the Natio

19、nal Committees for endorsement prior to publication as an International Standard. Publication as an International Standard requires approval by at least 50% of IDF National Committees casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject

20、of patent rights. IDF shall not be held responsible for identifying any or all such patent rights. ISO 12081IDF 36 was prepared by the International Dairy Federation (IDF) and Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products. It is being published jointly by ID

21、F 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 composition. This edition of ISO 12081IDF 36 cancels and replaces IDF 36A:1992, of which it constitutes a minor revision. BS ISO 12081:2010INTE

22、RNATIONAL STANDARD ISO 12081:2010(E)IDF 36:2010(E) ISO and IDF 2010 All rights reserved 1Milk Determination of calcium content Titrimetric method 1 Scope This International Standard specifies a titrimetric method for the determination of the calcium content of milk and of milk reconstituted from eva

23、porated, condensed or dried milk. 2 Terms and definitions For the purposes of this document, the following terms and definitions apply. 2.1 calcium content in milk mass fraction of substances determined by the procedure specified in this International Standard NOTE The calcium content is expressed a

24、s a percentage mass fraction. 3 Principle The protein substances in a test portion are precipitated by trichloroacetic acid, then filtered. The calcium in the filtrate is precipitated as calcium oxalate and is separated by centrifuging. The washed and dissolved precipitate is titrated with potassium

25、 permanganate. 4 Reagents and materials Unless otherwise specified, use only reagents of recognized analytical grade and distilled or demineralized water or water of equivalent purity. 4.1 Trichloroacetic acid solution I (C2HCl3O2), 200 g/l. 4.2 Trichloroacetic acid solution II, 120 g/l. 4.3 Ammoniu

26、m oxalate (C2H8N2O4), saturated solution, cold. 4.4 Methyl red solution. Dissolve 0,05 g of methyl red (C15H15N3O2) in 100 ml of ethanol (96 % volume fraction). 4.5 Acetic acid solution (C2H4O2), 20 % volume fraction. 4.6 Ammonia solution I. Mix equal volumes of ammonia (NH3) solution (25 % mass fra

27、ction) and water. BS ISO 12081:2010ISO 12081:2010(E) IDF 36:2010(E) 2 ISO and IDF 2010 All rights reserved4.7 Ammonia solution II. Dilute 2 ml of ammonia solution (25 % mass fraction) with water to 100 ml. 4.8 Sulfuric acid (H2SO4). Add 20 ml of sulfuric acid (98 % mass fraction) to 80 ml of water.

28、4.9 Potassium permanganate standard volumetric solution, c(KMnO4) = 0,004 mol/l 0,000 1 mol/l. Check the titre by normal laboratory procedure using oxalic acid or sodium oxalate. 5 Apparatus and materials Usual laboratory equipment and in particular the following. 5.1 Analytical balance, capable of

29、weighing to the nearest 0,01 g, with a readability of 0,001 g. 5.2 One-mark volumetric flask, capacity 50 ml, ISO 10424class A. 5.3 Pipette, capacity 20 ml, ISO 6482class A. 5.4 Centrifuge, capable of producing a radial acceleration of 1 400g. 5.5 Centrifuge tubes, cylindrical and round bottomed, ca

30、pacity about 30 ml, graduated at 20 ml. 5.6 Pipettes, capacities 2 ml and 5 ml, ISO 6482class A. 5.7 Suction device, with capillary tube. 5.8 Water bath, capable of maintaining water at boiling point. 5.9 Burette, graduated in 0,02 ml divisions, ISO 3851class A. 5.10 Filter paper, ashless, for slow

31、filtration. 6 Sampling Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in ISO 707|IDF 503. It is important that the laboratory receive a truly representative sample which has not been damaged or changed during transport or storage.

32、7 Preparation of test sample Bring the test sample of milk or reconstituted milk to a temperature of 20 C 2 C and mix carefully. If a homogeneous dispersion of the fat is not obtained, heat the sample slowly to 40 C, then mix gently by repeated inversion and cool to 20 C 2 C. BS ISO 12081:2010ISO 12

33、081:2010(E) IDF 36:2010(E) ISO and IDF 2010 All rights reserved 38 Procedure 8.1 Test portion Transfer approximately 20 g of the prepared test sample (see Clause 7) to the volumetric flask (5.2), using the pipette (5.3). Weigh the sample to the nearest 0,01 g. 8.2 Determination 8.2.1 Precipitation o

34、f protein substances Gradually add, while shaking, trichloroacetic acid solution I (4.1) to the test portion (8.1) until a volume of 50 ml is obtained. Shake vigorously for a few seconds and allow to stand for 30 min. Filter through the filter paper (5.10), taking care that the filtrate obtained is

35、clear. 8.2.2 Precipitation of calcium as oxalate and separation of the oxalate Pipette (5.6) 5 ml of the clear filtrate (see 8.2.1), 5 ml of trichloroacetic acid solution II (4.2), 2 ml of ammonium oxalate solution (4.3), two drops of methyl red solution (4.4) and 2 ml of acetic acid solution (4.5)

36、into a centrifuge tube (5.5). Mix by swirling. Add ammonia solution I (4.6) drop by drop to the mixed solutions in the tube until the colour becomes pale yellow. Then add a few drops of acetic acid solution (4.5) until a pink coloration appears. Allow to stand for 4 h at room temperature. Dilute the

37、 contents of the centrifuge tube with water to 20 ml. Centrifuge the tube at 1 400g for 10 min. Remove the clear supernatant liquid from the centrifuge tube with the suction device (5.7). Rinse the walls of the centrifuge tube with 5 ml of ammonia solution II (4.7), taking care not to disturb the de

38、posit of calcium oxalate. Centrifuge the tube at 1 400g again for 5 min. Remove the supernatant liquid from the centrifuge tube with the suction device (5.7). Repeat this washing operation twice. 8.2.3 Titration Add 2 ml of sulfuric acid (4.8) and 5 ml of water to the calcium oxalate deposit (see 8.

39、2.2). Place the tube in the boiling water bath (5.8) to dissolve the calcium oxalate deposit completely. Titrate the dissolved calcium oxalate with the potassium permanganate solution (4.9) until a pink colour persists. Take care that, during the titration, the temperature of the solution stays abov

40、e 60 C. Record the volume, in millilitres, of potassium permanganate solution used, to the nearest 0,01 ml. 8.2.4 Blank test Carry out a blank test in parallel with the determination by using 20 ml of water instead of the test portion. Record the volume, in millilitres, of potassium permanganate sol

41、ution used, to the nearest 0,01 ml. BS ISO 12081:2010ISO 12081:2010(E) IDF 36:2010(E) 4 ISO and IDF 2010 All rights reserved9 Calculation and expression of results 9.1 Calculation Calculate the calcium content, wCa, expressed as a percentage mass fraction, using the following equation: ()Ca 010000,0

42、00 4fwVVm= ()00, 4fVVm= where V is the volume, in millilitres, of potassium permanganate solution used for the test portion (see 8.2.3); V0is the volume, in millilitres, of potassium permanganate solution used for the blank test (see 8.2.4); m is the mass, in grams, of the test portion; f is the cor

43、rection factor, given in Table 1, for the volume of precipitate resulting from the trichloroacetic acid precipitation. Table 1 Correction factor, f, as a function of the fat content of the sample Fat content of the sample % mass fraction Correction factor f 3,5 to 4,5 0,972 3 0,976 2 0,980 1 0,985 0

44、,1 0,989 9.2 Expression of results Express the results to three decimal places. 10 Repeatability The absolute difference between two single test results, obtained using the same method on identical test material in the same laboratory by the same operator using the same equipment within a short inte

45、rval of time, will in not more than 5 % of cases be greater than 0,002 %. 11 Test report The test report shall contain at least the following information: a) all information necessary for the complete identification of the sample; b) the sampling method used, if known; BS ISO 12081:2010ISO 12081:201

46、0(E) IDF 36:2010(E) ISO and IDF 2010 All rights reserved 5c) the test method used, with reference to this International Standard (ISO 12081|IDF 36:2010); d) any operating conditions not specified in this International Standard, or regarded as optional, as well as details of any incidents which may h

47、ave influenced the test result(s); e) the test result(s) obtained; f) if the repeatability has been checked, the final quoted result obtained. BS ISO 12081:2010ISO 12081:2010(E) IDF 36:2010(E) 6 ISO and IDF 2010 All rights reservedBibliography 1 ISO 385, Laboratory glassware Burettes 2 ISO 648, Labo

48、ratory glassware Single-volume pipettes 3 ISO 707|IDF 50, Milk and milk products Guidance on sampling 4 ISO 1042, Laboratory glassware One-mark volumetric flasks BS ISO 12081:2010BS ISO 12081:2010ISO 12081:2010(E) IDF 36:2010(E) ICS 67.100.10 Price based on 6 pages ISO and IDF 2010 All rights reserved BS ISO 12081:2010This page has been intentionally left blank BS ISO12081:2010BSI GroupHeadquarters 389Chiswick High Road,London, W4 4AL, UKTel +44 (0)20 8996 9001Fax +44 (0)20 8996 - British Standards InstitutionBSI is the independent national body responsible for preparing BritishSt