BS ISO 15648-2004 Butter - Determination of salt content - Potentiometric method《黄油 盐含量的测定 电势滴定法》.pdf

1、BRITISH STANDARD BS ISO 15648:2004 Butter Determination of salt content Potentiometric method ICS 67.100.20 BS ISO 15648:2004 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 4 October 2004 BSI 4 October 2004 ISBN 0 580 44533 X National forewo

2、rd This British Standard reproduces verbatim ISO 15648:2004 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee AW/5, Milk and milk products, which has the responsibility to: A list of organizations represented on this committee

3、 can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility

4、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 responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. ai

5、d enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages Th

6、is document comprises a front cover, an inside front cover, the ISO title page, pages ii to iv, pages 1 to 7 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date Comments Reference numbers

7、 ISO 15648:2004(E) IDF 179:2004(E) OSI DI dnaF 4002INTERNATIONAL STANDARD ISO 15648 IDF 179 First edition 2004-08-15 Butter Determination of salt content Potentiometric method Beurre Dtermination de la teneur en sel Mthode potentiomtrique BSISO15648:2004IS:84651 O4002(E) ID:971 F4002(E) DPlcsid Frem

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13、ilni off-lidif.org We bwww.is.o gro We bwww.fil-idf.o gr Plbuisdehi n Switlrez dnaii ISO dnaID 4002 FA ll rihgtsser edevrBSISO15648:2004IS:84651 O4002(E) ID:971 F4002(E) I SO dna ID 4002 F All irhgts seredevr iiiForeword ISO (the International Organization for Standardization) is a worldwide federat

14、ion 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 committe

15、e. 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. International Standards are drafted in accordance

16、with the rules given in the ISO/IEC Directives, Part 2. 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. Attention is draw

17、n 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 15648|IDF 179 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk produ

18、cts, and the International Dairy Federation (IDF), in collaboration with AOAC International. It is being published jointly by ISO and IDF and separately by AOAC International. BSISO15648:2004IS:84651 O4002(E) ID:971 F4002(E) iv I SO dna ID 4002 F All irhgts seredevrForeword IDF (the International Da

19、iry Federation) is a worldwide federation of the dairy sector with a National Committee in every member country. Every National Committee has the right to be represented on the IDF Standing Committees carrying out the technical work. IDF collaborates with ISO and AOAC International in the developmen

20、t of standard methods of analysis and sampling for milk and milk products. Draft International Standards adopted by the Action Teams and Standing Committees are circulated to the National Committees for voting. Publication as an International Standard requires approval by at least 50% of IDF Nationa

21、l Committees casting a vote. ISO 15648|IDF 179 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC International. It is being published jointly by ISO and IDF and separately

22、by AOAC International. All work was carried out by the Joint ISO/IDF/AOAC Action Team on Minor compounds, of the Standing Committee on Minor components and characterization of physical properties, under the aegis of its project leader, Mr G. Brthen (NO). BSISO15648:2004NITERNATNOIAL STANDARD IS:8465

23、1 O4002(E) ID:971 F002(4)EI SO dna ID 4002 F All irhgts seredevr 1Butter Determination of salt content Potentiometric method 1 Scope This International Standard specifies a method for the determination of the salt content of all types of butter containing more than 0,1 % (mass fraction) salt. NOTE I

24、f the method is used for the analysis of butter with a low salt content, the expected relative precision figure will be higher than for salted butter; see also Reference 4. 2 Terms and definitions For the purposes of this document, the following terms and definitions apply. 2.1 salt content of butte

25、r mass fraction of substances determined by the procedure specified in this International Standard NOTE The salt content, being the equivalent of sodium chloride, is expressed in percent by mass. 3 Principle A test portion is suspended in water. Chloride ions are titrated potentiometrically with a s

26、tandard volumetric solution of silver nitrate. 4 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water free from chloride, or water of equivalent purity. 4.1 Silver nitrate, standard volumetric solution, of concentration in the ra

27、nge of c(AgNO 3 ) = 0,08 mol/l to 0,12 mol/l. Dissolve 13,6 g to 20,4 g of silver nitrate in water which is practically free from carbon dioxide. Dilute to 1 000 ml. Standardize the silver nitrate standard volumetric solution against sodium chloride (NaCl), previously dried at 300 C for 2 h. Express

28、 the concentration of the silver nitrate standard volumetric solution to four decimal places. Store the solution protected from direct sunlight. Commercially available solutions may be used. 4.2 Nitric acid solution, c(HNO 3 ) 4 mol/l. BSISO15648:2004IS:84651 O4002(E) ID:971 F4002(E) 2 I SO dna ID 4

29、002 F All irhgts seredevr5 Apparatus Usual laboratory apparatus and, in particular, the following. 5.1 Analytical balance, capable of weighing to the nearest 1 mg, with a readability of 0,1 mg. 5.2 Potentiometer, provided with a measuring electrode suitable for the determination of chloride (e.g. a

30、silver electrode) and a reference electrode e.g. a mercury(I) sulfate electrode. 5.3 Vessel, suitable for blending and titration. 5.4 Graduated cylinders, of capacities 50 ml and 100 ml. 5.5 Burette, of capacity 50 ml, graduated in 0,1 ml, or, preferably, an automatic plunger burette, readable to th

31、e nearest 0,01 ml, both made of brown glass or protected from light. 5.6 Stirrer. Suitable (semi) automatic titration apparatus may be used for 5.2 to 5.6. 5.7 Spoon or spatula. 6 Sampling It is important that the laboratory receive a sample which is truly representative and has not been damaged or

32、changed during transport or storage. Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in ISO 707. Store the sample in such a way that deterioration and change in its composition are prevented. 7 Preparation of test sample Take a repr

33、esentative test sample. If the test sample is visibly not homogeneous, or if the history of the test sample (age, storage conditions) is such that inhomogeneity is expected, homogenize the sample as follows. a) Warm the test sample in the original unopened container, which should be from one-half to

34、 two-thirds full, to a temperature at which the sample will be soft enough to facilitate thorough mixing to a homogeneous state (either by a mechanical shaker or by hand). Take care that the mixing temperature does not exceed 30 C. b) Cool the test sample to ambient temperature with constant mixing

35、until cooling is complete. As soon as possible thereafter, open the sample container and stir briefly (no longer than for 10 s) with a suitable device, for example a spoon or spatula (5.7), before weighing. 8 Procedure 8.1 Test portion Weigh, to the nearest 1 mg, 2 g to 4 g of the test sample (Claus

36、e 7) into the vessel (5.3). Record the mass to 0,1 mg. BSISO15648:2004IS:84651 O4002(E) ID:971 F4002(E) I SO dna ID 4002 F All irhgts seredevr 38.2 Determination 8.2.1 Add 100 ml of boiling water or 100 ml of cold water and heat to boiling to dissolve the test portion. Cool the obtained suspension t

37、o below 55 C. Put the measuring electrode and the reference electrode of the potentiometer (5.2) into the suspension. Titrate the suspension with the silver nitrate standard volumetric solution (4.1) using the burette (5.5). Stir continuously until the endpoint has nearly been reached. Then titrate

38、cautiously until the endpoint is reached. NOTE The endpoint corresponds to the maximum potential difference which is observed between two successive equal additions (of about 0,05 ml) of the silver nitrate standard volumetric solution. 8.2.2 In the case of a difficult titration, the addition of 2 ml

39、 to 3 ml of nitric acid solution (4.2) to the contents of the vessel before titration is allowed. By testing this in the collaborative study (see Annex A), it was shown that the same level of precision was attained. 8.3 Blank test Carry out a blank test using all reagents but omitting the test porti

40、on. 9 Calculation and expression of results 9.1 Calculation Calculate the salt content of the test sample, w, expressed as a percentage by mass, using the following equation: 10 () 5 , 8 4 VV c w m = where V 0is the volume of the silver nitrate standard volumetric solution used in the blank test, in

41、 millilitres (see 8.3), V 1is the volume of the silver nitrate standard volumetric solution used in the determination, in millilitres (see 8.2); c is the numerical value of the actual concentration of the silver nitrate standard volumetric solution, in moles per litre; 5,84 is the factor transformin

42、g the experimentally obtained amount of Cl into salt (NaCl); m is the mass of the test portion, in grams (see 8.1). 9.2 Expression of results Express the test results to two decimal places. BSISO15648:2004IS:84651 O4002(E) ID:971 F4002(E) 4 I SO dna ID 4002 F All irhgts seredevr10 Precision 10.1 Int

43、erlaboratory test Details of an interlaboratory test on the precision of the method are summarized in Annex A. The values derived from this interlaboratory test may not be applicable to concentration ranges and matrices other than those given. 10.2 Repeatability The absolute difference between two i

44、ndependent 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 interval of time, will in not more than 5 % of cases be greater than a mass fraction of 0,05 %. 10.3 Reproducibility The absol

45、ute difference between two single test results, obtained using the same method on identical test material in different laboratories with different operators using different equipment, will in not more than 5 % of cases be greater than a mass fraction of 0,08 %. 11 Test report The test report shall s

46、pecify: a) all information necessary for the complete identification of the sample; b) the sampling method used, if known; c) the test method used, with reference to this International Standard; d) all operational details not specified in this International Standard, or regarded as optional, togethe

47、r with details of any incidents which may have influenced the test result(s); e) the test result(s) obtained and, if the repeatability has been checked, the final quoted result obtained. BSISO15648:2004IS:84651 O4002(E) ID:971 F4002(E) I SO dna ID 4002 F All irhgts seredevr 5Annex A (informative) Re

48、sults of the interlaboratory test A.1 An international collaborative test involving eleven laboratories was carried out on six butter samples, each divided in two equal samples (blind duplicates) so as to obtain 12 test samples. The Norwegian Institute for Food and Environmental Analysis organized t

49、he test. The results obtained were subjected to statistical analysis in accordance with ISO 5725-1 and ISO 5725-2 to give the precision data shown in Table A.1. Based on the obtained results, the repeatability limit, r, was set at 0,05 %. The reproducibility limit, R, was set at 0,08 % Table A.1 Interlaboratory test results Butter samples A B C D E F Mean bNo. of participating laboratories left after eliminating outliers 10 10 10 11