BS 5766-11-1986 Methods for analysis of animal feeding stuffs Determination of calcium by titration《动物饲料分析方法 第11部分 滴定法测定钙》.pdf

1、BRITISH STANDARD BS 5766-11: 1986 ISO 6490-1: 1985 Methods for Analysis of animal feeding stuffs Part 11: Determination of calcium by titration ISO title: Animal feeding stuffs Determination of calcium content Part 1: Titrimetric method UDC 636.085:546.41:543.242.5BS5766-11:1986 This British Standar

2、d, having been prepared under the directionof the Food and Agriculture Standards Committee,was published underthe authority of the BoardofBSI and comes intoeffecton 28November1986 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference FAC/14 Draft for comme

3、nt 83/56072 DC ISBN 0 580 15443 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Food and Agriculture Standards Committee (FAC/-) to Technical Committee FAC/14, upon which the following bodies were represented: Association of Public Ana

4、lysts Department of Trade and Industry (Laboratory of the Government Chemist) Grain and Feed Trade Association Limited Ministry of Agriculture, Fisheries and Food National Farmers Union Overseas Development Administration (Tropical Development and Research Institute) Pet Food Manufacturers Associati

5、on Royal Association of British Dairy Farmers United Kingdom Agricultural Supply Trade Association Ltd. United Kingdom Renderers Association Ltd. Amendments issued since publication Amd. No. Date of issue CommentsBS5766-11:1986 BSI 12-1999 i Contents Page Committees responsible Inside front cover Na

6、tional foreword ii 1 Scope and field of application 1 2 References 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Sampling 1 7 Procedure 1 8 Expression of results 2 9 Notes on procedure 2 10 Test report 2 Publications referred to Inside back coverBS5766-11:1986 ii BSI 12-1999 National foreword This Pa

7、rt of BS5766 has been prepared under the direction of the Food and Agriculture Standards Committee. It is identical with ISO6490-1:1985 “Animal feeding stuffs Determination of calcium content Part1: Titrimetric method” published by the International Organization for Standardization (ISO), in the pre

8、paration of which the United Kingdom played a full part. In the United Kingdom, animal feeding stuffs are controlled by legislation. The method in this Part of BS5766 is technically equivalent to the method given in the Feeding Stuffs (Sampling and analysis) Regulations1982, SI1982 No. 1144 1) . Ter

9、minology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following. The

10、 comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. In British Standards it is current practice to use the symbol “L” for litre (and in its submultiples) rather than “l” and to use the spelling “sulphur”, et

11、c. instead of “sulfur”, etc. Wherever the words “International Standard” and “part of ISO6490” appear, referring to this standard, they should be read as “Part of BS5766”. When ISO6497, referred to inclause6, is published it is intended to implement it as a dual-numbered (identical) British Standard

12、. In the meantime, parties concerned are recommended to reach agreement on sampling. The Technical Committee has reviewed the relevant provisions of ISO6498:1983, referred to in7.1 and has decided that they are acceptable for use in conjunction with this standard. The United Kingdom did not approve

13、ISO6498 but, in the present context, samples prepared in accordance with either ISO6498 or BS5766 “Methods for analysis of animal feedings stuffs” Part 10 “Preparation of test samples” are equally acceptable. A British Standard does not purport to include all the necessary provisions of a contract.

14、Users of British Standards are responsible for their 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, pagesi andii, pages1 and2, an inside back cover and a

15、 back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. 1) Published by HMSO. Cross-references International Standard Corresponding British Standard ISO 6490-2:1983 BS 5766 Met

16、hods for analysis of animal feeding stuffs Part 6:1984 Determination of calcium by atomic absorption spectrometry (Identical)BS5766-11:1986 BSI 12-1999 1 1 Scope and field of application This part of ISO6490 specifies a titrimetric method for the determination of the calcium content of animal feedin

17、g stuffs. The method is applicable to all animal feeding stuffs having calcium contents greater than1g/kg. 2 References ISO 6490-2, Animal feeding stuffs Determination of calcium content Part 2: Atomic absorption spectrometric method. ISO 6497, Animal feeding stuffs Sampling 2) . ISO 6498, Animal fe

18、eding stuffs Preparation of test samples. 3 Principle Ashing of a test portion, treatment of the ash with hydrochloric acid and precipitation of the calcium as calcium oxalate. Dissolution of the precipitate in sulfuric acid and titration with standard volumetric potassium permanganate solution of t

19、he oxalic acid formed. 4 Reagents All reagents shall be of recognized analytical quality and the water used shall be distilled water or water of at least equivalent purity. 4.1 Hydrochloric acid, approximately30% (m/m) ( 20= 1,15g/ml). 4.2 Nitric acid, concentrated ( 20= 1,40g/ml). 4.3 Sulfuric acid

20、, approximately20% (m/m) ( 20= 1,13g/ml). 4.4 Ammonia solution, approximately33% (m/m) ( 20= 0,89g/ml). 4.5 Ammonium oxalate, cold saturated solution. 4.6 Citric acid monohydrate, 300g/l solution. 4.7 Ammonium chloride, 50g/l solution. 4.8 Bromocresol green, 0,4g/l solution. 4.9 Potassium permangana

21、te, standard volumetric solution, c (1/5 KMnO 4 )=0,1mol/l. 5 Apparatus Usual laboratory apparatus, and in particular 5.1 Electric muffle furnace, with air circulation, capable of being maintained at550 20 C. 5.2 Incineration dish, made of platinum, silica or porcelain. 5.3 Sintered glass filter cru

22、cible, of porosity grade P16 (pore size10 to164m). 5.4 Boiling water-bath 5.5 Beakers, of capacity250ml. 5.6 Volumetric flask, of capacity250ml. 5.7 Analytical balance 6 Sampling Take the laboratory sample as specified in ISO6497. 7 Procedure 7.1 Preparation of the test sample Prepare the test sampl

23、e in accordance with ISO6498. 7.2 Test portion Weigh, to the nearest1mg, approximately5g of the test sample (or more if necessary), into the incineration dish (5.2). 7.3 Determination 7.3.1 Ash the test portion in the electric muffle furnace (5.1), maintained at550 20 C, until all organic matter has

24、 been destroyed (usually4h is sufficient). If some organic matter remains (black particles), add a few drops of nitric acid (4.2), dry on a hotplate and ash again in the muffle furnace at550 20 C for30min. Repeat this until all organic matter has been destroyed. Transfer the ash to a250ml beaker (5.

25、5). 7.3.2 Add40ml of the hydrochloric acid (4.1), 60ml of water, and a few drops of the nitric acid (4.2). Bring to the boil and boil for30min. Cool and transfer the solution to a250ml one-mark volumetric flask (5.6). Rinse, dilute to the mark with water, mix and filter to give the test solution. 7.

26、3.3 By means of a pipette, transfer an aliquot portion of the test solution (7.3.2), containing10 to40mg of calcium, according to the expected calcium content, to a250ml beaker (5.5). Add1ml of the citric acid solution (4.6) and5ml of the ammonium chloride solution (4.7). Dilute to approximately100m

27、l with water. Bring to the boil, add10drops of the bromocresol green solution (4.8) and30ml of a warm solution of the ammonium oxalate (4.5). If a precipitate forms, dissolve it by adding a few drops of the hydrochloric acid (4.1). 2) At present at the stage of draft.BS5766-11:1986 2 BSI 12-1999 Neu

28、tralize very slowly with the ammonia solution(4.4), stirring continuously, until a pH of4,4 to4,6 is reached (i.e.when the indicator changes colour). Place the beaker on a boiling water-bath (5.4) and leave for30min to allow the precipitate which has formed to settle. Remove the beaker from the wate

29、r bath. Leave for1h and filter through the filter crucible (5.3). Wash the beaker and the crucible with water until the excess ammonium oxalate is completely removed as shown by the absence of chloride in the washing water. Place the crucible in a250ml beaker (5.5) or wide-mouth flask. Add80ml of th

30、e sulfuric acid (4.3) and heat to70 to80 C to dissolve the precipitate. 7.3.4 Titrate the hot solution with the standard volumetric potassium permanganate solution (4.9), until a pink colour, persisting for1min, is obtained. 7.4 Number of determinations Carry out two determinations on test portions

31、taken from the same test sample. 8 Expression of results 8.1 Method of calculation and formula The calcium content, expressed in grams per kilogram of sample, is equal to where V is the volume, in millilitres, of the standard volumetric potassium permanganate solution used for the titration; c is th

32、e exact concentration, in moles per litre, of the standard volumetric potassium permanganate solution; m is the mass, in grams, of the test portion; V is the volume, in millilitres, of the aliquot portion taken in7.3.3. Take as the result the arithmetic mean of the values obtained in the two determi

33、nations (see7.4), provided that the requirement for repeatability (see8.2) is satisfied. Report the result to the nearest1g/kg. 8.2 Repeatability The difference between the values obtained in the two determinations, carried out simultaneously or in rapid succession by the same analyst, shall not exc

34、eed 1g/kg (absolute) for calcium contents less than50g/kg; 2% (relative) of the mean for calcium contents of50g/kg or more. 9 Notes on procedure 9.1 For the determination of very low calcium contents use the method specified in ISO6490-2. 9.2 If the sample consists exclusively of mineral substances,

35、 dissolve it in hydrochloric acid without ashing. For products such as aluminocalcium phosphates, which are difficult to dissolve in acids, mix the test portion in a platinum dish with five times its mass of a mixture comprising equal parts of potassium carbonate and sodium carbonate. Heat carefully

36、 until the mixture is completely molten. After cooling, dissolve in the hydrochloric acid. 9.3 If the magnesium content of the sample is likely to exceed the calcium content, or in cases of doubt, precipitate the calcium oxalate a second time. 10 Test report The test report shall show the method use

37、d and the result obtained. It shall also mention any operating conditions not specified in this International Standard, or regarded as optional, as well as any circumstances that may have influenced the results. The test report shall include all the details required for the complete identification o

38、f the sample.BS5766-11:1986 BSI 12-1999 Publications referred to See national foreword.BS 5766-11: 1986 ISO 6490-1: 1985 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on

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