1、BRITISH STANDARD BS 1741-11: 1989 Methods for Chemical analysis of liquid milk and cream Part 11: Detection of detergent/disinfectant residues UDC 637.12 + 637.148.074:543BS1741-11:1989 This British Standard, having been prepared under the directionof the Dairying Standards Committee, was published
2、under the authority ofthe Board of BSI and comes intoeffect on 31 July 1989 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference DAC/3 Draft for comment 87/55546 DC ISBN 0 580 17099 3 Committees responsible for this British Standard The preparation of thi
3、s British Standard was entrusted by the Dairying Standards Committee (DAC/-) to Technical Committee DAC/3, upon which the following bodies were represented: AFRC Institute of Food Research (Reading Laboratory) Association of British Preserved Milk Manufacturers Association of Public Analysts Associa
4、tion of Public Analysts of Scotland Creamery Proprietors Association Department of Trade and Industry (Laboratory of the Government Chemist) Ice Cream Alliance Limited Intervention Board for Agricultural Produce Joint Committee of the Milk Marketing Board and the Dairy Trade Federation Milk Marketin
5、g Board Milk Marketing Board for Northern Ireland Ministry of Agriculture, Fisheries and Food Royal Association of British Dairy Farmers Royal Society of Chemistry Society of Chemical Industry Society of Dairy Technology Amendments issued since publication Amd. No. Date of issue CommentsBS1741-11:19
6、89 BSI 07-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Sampling and test samples 1 3 Detection of chlorate 1 4 Detection of quaternary ammonium compounds 1 5 Detection of iodine in milk 2 6 Test report 2 Publication referred to Inside back coverBS1741-11:198
7、9 ii BSI 07-1999 Foreword This Part of BS 1741 has been prepared under the direction of the Dairying Standards Committee. It is a revision of the methods described previously inB.6, B.7 and B.8 of BS 4285:1968, which are withdrawn by amendment. This Part includes methods for the detection of chlorat
8、e, quaternary ammonium compounds and iodine in milk. The disinfectants and detergent/disinfectants most commonly used in the dairying industry are based on chlorine compounds, quaternary ammonium compounds or iodophors. However, chlorine compounds approved for use in the cleaning of dairy plant and
9、equipment are required to contain chlorate as a tracer. Residues of iodophors, which are made by complexing iodine with suitable non-ionic surface active agents, are traced by detecting free iodine. NOTEThis Part should be read in conjunction with Part 1 “General introduction including preparation o
10、f samples”, published separately. A British Standard does not purport to include all the necessary provisions of a contract. 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
11、 of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 and 2, an inside back cover and a 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
12、 cover.BS1741-11:1989 BSI 07-1999 1 1 Scope This Part of BS 1741 describes methods for the detection of residues of chlorate, quaternary ammonium compounds and iodophors in liquid milk. NOTEThe title of the publication referred to in this Part of BS1741 is given on the inside back cover. 2 Sampling
13、and test samples Take a representative sample of the liquid milk to be tested using, where appropriate, the procedures described in BS 1741-1. 3 Detection of chlorate 3.1 Introduction Chlorine compounds used for the cleaning of dairy plant and equipment contain chlorate (see the foreword). A minimum
14、 of0.7% (m/m) sodium chlorate is present in hypochlorites approved for use in the dairying industry on despatch from the manufacturer. The amount slowly increases with storage. Estimation of the amount of chlorine compounds in milk on the basis of chlorate content is not therefore reliable and the m
15、ethod described herein is for detecting chlorate, expressed as sodium chlorate, at levels of0.3mg/L and above. 3.2 Reagent 3.2.1 Sulphuric acid containing tin (II) chloride. Dissolve 0.025 g of tin (II) chloride in 25.0mL of water and carefully add 75.0 mL of concentrated sulphuric acid, , 20 C = 1.
16、84 g/mL. 3.3 Apparatus 3.3.1 Ordinary laboratory apparatus. 3.3.2 Centrifuge, capable of operating at approximately 2500 r/min. 3.3.3 Test tubes, of size 150 mm 19 mm. 3.3.4 Centrifuge tubes, of capacity about 13 mL. 3.3.5 Mercury vapour lamp fitted with a Woods filter. 3.4 Procedure To 3 mL of the
17、test sample (see clause 2) in a test tube (3.3.3) cooled to 0.5 C add 3 mL of the sulphuric acid (3.2.1), also cooled to 0.5 C. Agitate the tube thoroughly in a freezing mixture of ice and salt and allow to stand in the freezing mixture for3min. Transfer the contents to a centrifuge tube(3.3.4) and
18、spin for 3 min at approximately2500 r/min in the centrifuge (3.3.2). Examine the tube immediately in ultraviolet light from a mercury vapour lamp fitted with a Woods filter (3.3.5) for the presence of any yellow fluorescence, which indicates the presence of chlorate in the milk. Set up two control t
19、ubes for each batch of samples, one from a milk supply known to be free from sodium hypochlorite and the other from milk containing approved hypochlorite calculated to give20 mg/kg of available chlorine. Do not allow the contents of the tubes to freeze. NOTEMilk which gives a positive test when fres
20、h may give a negative one after storing, but the apparent decrease in chlorate content is not appreciable until the milk coagulates when 1 mL is added to 1 mL of 68% (V/V) ethanol. 3.5 Result If the tubes containing the control samples produced the expected results, record whether the presence of ch
21、lorate was or was not indicated for each test sample. If not, repeat the test using fresh reagents. 4 Detection of quaternary ammonium compounds 4.1 Introduction The method describes a procedure for the detection of quaternary ammonium compounds (QACs) but an approximate estimation of the amount of
22、QACs present can also be made if larger residues are present. The method is capable of detecting QAC residues of 1 mg/kg and above. 4.2 Reagents 4.2.1 1,1,2,2-Tetrachloroethane. Store in a brown glass bottle in the dark. CAUTION. The solution gives off a toxic vapour. 4.2.2 Lactic acid solution, 50%
23、 (m/m). Dilute 57g of lactic acid about 88% (m/m) to 100 g with water. 4.2.3 Eosin 1) , 0.5 g/L solution. Dissolve 25 mg of eosin in 50 mL water. 4.2.4 Sodium hydroxide, 128 g/L solution. Dissolve32 g of sodium hydroxide in water and dilute to 250 mL. 4.2.5 Citric acid buffer solution, pH 4.5. Disso
24、lve25g of citric acid in 75 mL of water and adjust to pH 4.5 by adding 500 g/L sodium hydroxide solution (about 13 mL). 4.2.6 Anionic detergent reagent stock solution. Dissolve 0.45 0.01 g of docusate sodium in water and dilute to the mark in a 1000 mL one-mark volumetric flask. 4.2.7 Anionic deterg
25、ent reagent working solution. Prepare a tenfold dilution of the stock solution of anionic detergent reagent (4.2.6). 1) 2,4,5,7-tetrabromo-3,6-dihydroxyspiro isobenzofuran-1 (3H), 9-xanthen-3-one.BS1741-11:1989 2 BSI 07-1999 4.3 Apparatus 4.3.1 Ordinary laboratory apparatus. 4.3.2 Test tubes, of siz
26、e 150 mm 19 mm, with cork or glass stoppers. 4.3.3 Centrifuge, 25 cm diameter and capable of operating at 3200 r/min (or a machine giving an equivalent centrifugal force). 4.3.4 Centrifuge tubes, suitable for the centrifuge(4.3.3), together with cork or glass stoppers. 4.4 Procedure Place 5 mL of 1,
27、1,2,2-tetrachloroethane (4.2.1),2mL of lactic acid solution (4.2.2) and 5 mL of the test sample (see clause 2) in a test tube (4.3.2) fitted with a cork or glass stopper. Shake vigorously for 1 min. Add 2 mL of the sodium hydroxide solution (4.2.4), invert six times and shake for 30 s. Transfer to a
28、 centrifuge tube (4.3.4) fitted with a cork or glass stopper. Centrifuge at 3200 r/min in the centrifuge (4.3.3) for 5 min. NOTE 1Three distinct layers will be formed. Decant or aspirate off the top aqueous layer. Loosen the middle layer, consisting chiefly of white precipitated protein, using a thi
29、n glass rod and pour or pipette off as much as possible of the bottom layer, which consists of clear 1,1,2,2-tetrachloroethane containing any QAC originally in the milk sample, to another test tube. Transfer 2 mL of this 1,1,2,2-tetrachloroethane to a clean test tube (4.3.2) containing 0.5 mL of the
30、 citric acid buffer solution (4.2.5) and 0.2 mL of the eosin solution (4.2.3). Close the tube and shake vigorously for a few seconds. If a pink or red colour is obtained in the 1,1,2,2-tetrachloroethane then assume the presence of QAC. NOTE 2Samples of milk containing about 1 mg/kg of QAC develop a
31、faint pink colour, which can be distinguished from a control prepared by using milk known to be free from QAC. If a deep pink or red colour is observed, it is permissible to make an approximate estimation of the amount of QAC present by titrating with anionic detergent reagent working solution (4.2.
32、7) until the pink colour disappears. Calculate the concentration of QAC present using the relationship that 1 mL of the anionic detergent reagent working solution is equivalent to M/20 mg/kg QAC in 2 mL sample, where M is the equivalent mass (usually the relative molecular mass) of the QAC. 4.5 Resu
33、lt Record whether the presence of QACs was or was not indicated for each test sample. If an estimation of the QACs present was made, record the result in milligrams per kilogram and indicate that it is estimated. 5 Detection of iodine in milk 5.1 Introduction This method is qualitative: it cannot be
34、 used for the quantitative estimation of the iodine but it is possible to detect 5 mg/kg to 10 mg/kg of iodine in milk. 5.2 Reagents 5.2.1 Concentrated hydrochloric acid, ,20C=1.16g/mL. 5.2.2 Colour reagent, benzaflavone 2) , 5 g/L solution, in a mixture of equal volumes of 95% (V/V) ethanol and of
35、diethyl ether. Store the solution in the refrigerator and discard when it becomes distinctly yellow. 5.2.3 Hydrogen peroxide, 60 g/L solution. 5.3 Apparatus 5.3.1 Ordinary laboratory apparatus. 5.3.2 Test tubes, of size 150 mm 16 mm. 5.4 Procedure Cool 1 mL of the test sample (see clause 2) in a tes
36、t tube (5.3.2) in iced water. Add 1 mL of the hydrochloric acid (5.2.1), mix by shaking and replace in the iced water. Add five drops of the colour reagent solution (5.2.2) followed by four to five drops of the hydrogen peroxide solution (5.2.3) and mix by shaking. If a lilac or blue colour develops
37、 within a few seconds assume the presence of more than 5 mg/kg of iodine. Prepare a control using milk known to be free from both iodophors and hypochlorite, for comparison. 5.5 Result If the tube containing the control produced the expected result, record whether the presence of iodine was or was n
38、ot indicated for the test sample. If not, repeat the test using fresh reagents. 6 Test report The test report shall be in accordance with BS 1741-1. 2) 2-phenylbenzohchromen-4-one.BS1741-11:1989 BSI 07-1999 Publication referred to BS 1741, Methods for chemical analysis of liquid milk and cream. BS 1
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