1、BRITISH STANDARD BS 4401-16: 1996 ISO 1841-2: 1996 Methods of test for Meat and meat products Part 16: Determination of chloride content (potentiometric method) ICS 67.120.10BS4401-16:1996 This British Standard, having been prepared under the direction of the Consumer Products and Services Sector Bo
2、ard, was published under theauthority of the Standards Board and comes into effect on 15 October 1996 BSI 11-1998 The following BSI references relate to the work on this standard: Committee reference AW/6 Draft for comment 94/504479 DC ISBN 0 580 26069 0 Committees responsible for this British Stand
3、ard The preparation of this British Standard was entrusted to Technical Committee AW/6, Chemical analysis of meat and meat products, upon which the following bodies were represented: Association of Public Analysts British Meat Manufacturers Association British Poultry Meat Federation Ltd. Department
4、 of Trade and Industry (Laboratory of the Government Chemist) Leatherhead Food Research Association Meat and Livestock Commission Ministry of Agriculture, Fisheries and Food National Federation of Meat and Food Traders Royal Society of Chemistry Worshipful Company of Butchers Amendments issued since
5、 publication Amd. No. Date CommentsBS4401-16:1996 BSI 11-1998 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Definition 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Sampling 1 7 Preparation of test sample 1 8 Procedure 2 9 Calculation 2 10 Precision 3 11 T
6、est report 3 Annex A (informative) Bibliography 4 List of references Inside back coverBS4401-16:1996 ii BSI 11-1998 National foreword This Part of BS 4401 has been prepared by Technical Committee AW/6 and is identical with ISO 1841-2:1996 Meal and meal products Determination of chloride content Part
7、 2: Potentiometric method published by the International Organization for Standardization (ISO) and in the preparation of which the United Kingdom played a full part. The Volhard method for the determination of chloride content of meat and meat products is given in BS 4401-6. ISO 5725:1986, to which
8、 informative reference is made in the text, has been superseded by ISO 5725-1:1994, ISO 5725-2:1994, ISO 5725-3:1994, ISO5725-4:1994 and ISO 5725-6:1994 which are identical with BS ISO 5725 Accuracy (trueness and precision) of measurement methods and results, BSISO5725-1:1994 General principles and
9、definitions, BS ISO 5725-2:1994 Basic methods for the determination of repeatability and reproducibility of a standard measurement method, BSISO5725-3:1994, Intermediate measures of the precision of a standard measurement method, BS ISO 5725-4:1994 Basic methods for the determination of the trueness
10、 of a standard measurement method, and BS ISO 5725-6:1994 Use in practice of accuracy values. 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 n
11、ot of itself confer immunity from legal obligations. Cross-references Publication referred to Corresponding British Standard Informative ISO 3100-1:1991 BS 5348 Methods for sampling meat and meat products Part 1:1991 Taking primary samples (Identical) Summary of pages This document comprises a front
12、 cover, an inside front cover, pages i and ii, pages 1 to 4, 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 theinside front cover.BS4401-16:1996 BSI 11-1998 1 1 Scop
13、e This part of ISO 1841 specifies a method for the determination of the chloride content of meat and meat products, including poultry, with sodium chloride contents equal to or greater than0,25%(m/m). 2 Definition For the purposes of this part of ISO 1841, the following definition applies. 2.1 chlor
14、ide content of meat and meat products total chloride content determined by the method specified in this part of ISO 1841. It is expressed as sodium chloride as a percentage by mass 3 Principle Dispersion of a test portion with water. Acidification of an aliquot of the suspension and potentiometric t
15、itration with a silver nitrate solution using a silver electrode. 4 Reagents Use only reagents of recognized analytical grade unless otherwise specified. 4.1 Water, distilled and halogen-free. Halogen-free test: Add 1 ml of silver nitrate c(AgNO 3 ) = 0,1 mol/l and 5 ml of nitric acid c(HNO 3 ) = 4
16、mol/l to 100 ml of water. No more than a slight turbidity shall be produced. 4.2 Nitric acid, 1 + 49 (V/V) solution. Dilute 20 ml of concentrated nitric acid (r 20= 1,40 g/ml) to 1 000 ml with water. 4.3 Silver nitrate, standard volumetric solution, c(AgNO 3 ) = 0,085 6 mol/l. Dissolve in water 14,5
17、41 g of silver nitrate, previously dried for 2 h at 150 C 2 C and allowed to cool in a desiccator. Transfer quantitatively to a1000 ml one-mark volumetric flask and dilute to the mark with water. Store this solution in a dark glass container out of direct sunlight. 4.4 Sodium chloride, standard volu
18、metric solution, c(NaCl) = 0,085 6 mol/l. Dissolve in water 5,000 g of sodium chloride, previously dried for 2 h at 110 C 2 C and allowed to cool in a desiccator. Transfer quantitatively to a1000 ml one-mark volumetric flask and dilute to the mark with water. 5 Apparatus Usual laboratory apparatus a
19、nd, in particular, the following. 5.1 Homogenizing equipment, mechanical or electrical, capable of homogenizing the test sample. This includes a high-speed rotational cutter, or a mincer fitted with a plate with holes not exceeding4,5mm in diameter. 5.2 Laboratory blender, equipped with a variable t
20、ransformer for blending at low and high rotational frequencies. 5.3 Electrodes, silver billet combination electrode, or separate indicating silver and glass reference electrodes. Before initial use and before each days use, if necessary, clean the silver billet electrode tip with scouring powder or
21、another suitable material and rinse thoroughly with water (hot water may be required with some types of samples). Clean other electrodes as recommended by the manufacturer. Reclean as necessary to prevent drifting of the endpoint reading. With some samples, periodically rinse the electrodes with wat
22、er and wipe with a tissue to prevent accumulation of film. It is unnecessary to coat silver billet electrodes with silver chloride. 5.4 Magnetic stirrer, capable of being adjusted to a constant rotational frequency. 5.5 pH-meter, preferably direct reading, with scale divisions 10mV or less; range at
23、 least 700 mV, e.g.digital type. 5.6 Pipette, of capacity 50 ml. 5.7 Analytical balance, capable of weighing to an accuracy of 0,1 g. 6 Sampling It is important that the laboratory receive a sample which is truly representative and has not been damaged or changed during transport or storage. Samplin
24、g is not part of the method specified in this part of ISO 1841. A recommended sampling method is given in ISO 3100-1. Proceed from a representative sample of at least200g. 7 Preparation of test sample 7.1 Homogenize the laboratory sample with the appropriate equipment (5.1). Take care that the tempe
25、rature of the sample material does not rise above 25 C. If a mincer is used, pass the sample at least twice through the equipment.BS4401-16:1996 2 BSI 11-1998 7.2 Fill a suitable airtight container with the prepared sample, close the container and store in such way that deterioration and change in c
26、omposition are prevented. Analyse the sample as soon as practicable, but always within 24 h of homogenization. 8 Procedure NOTE 1If it is required to check whether the repeatability requirement is met, carry out two single determinations in accordance with 8.1 to 8.4 under repeatability conditions.
27、8.1 Test portion Weigh, to the nearest 0,1 g, about 50 g of the test sample in a 1 000 ml blender jar. 8.2 Dispersion 8.2.1 Add 450 g of water (4.1) to the test portion(8.1). Cover the jar and start the blender(5.2) at low rotational frequency for the initial dispersion. Blend thoroughly at a high s
28、peed for 1 min to 2 min so that the solid material is uniformly suspended. 8.2.2 Pipette (5.6), immediately after blending,50ml of the thoroughly mixed sample suspension into a tared 250 ml beaker. Determine the mass of the test solution. Proceed as described in8.4. 8.3 Titration curve 8.3.1 Pipette
29、 25 ml of the sodium chloride solution(4.4) into a 250 ml beaker. Dilute to about50ml with the water (4.1) and add 50 ml of the dilute nitric acid (4.2). 8.3.2 Insert the electrodes (5.3) into the solution and start mixing. Stir throughout the titration at a constant rate producing vigorous agitatio
30、n without splashing. 8.3.3 Titrate with the silver nitrate solution (4.3), adjusting increments with the rate of change in potential (see 5.5) so that an accurate plot of change in potential in millivolts (y-axis) against volume in millilitres of the silver nitrate solution (x-axis) can be prepared.
31、 Add a total of 50ml of silver nitrate solution to obtain a complete titration curve. 8.3.4 Determine the inflection point by drawing two straight lines with a 45 slope with respect to the axes and tangent to the titration curve at two points of greatest curvature. NOTE 2The inflection point is at t
32、he intersection of the titration curve with the line drawn parallel to, and midway between, the other two lines. 8.3.5 Use the inflection point as the endpoint in titrating the sample solution (8.4). Recheck the endpoint potential occasionally with respect to a junction potential developing at the r
33、eference electrode. Redetermine the endpoint by preparing a new titration curve when either an individual electrode, a combination electrode, or the pH-meter is replaced. 8.3.6 From the volume of the silver nitrate solution used, calculate the concentration and adjust to0,085 6 mol/l. 8.4 Determinat
34、ion Add 50ml of the dilute nitric acid (4.2) and titrate as described in 8.3 for the sodium chloride solution. Use a 10 ml burette if the chloride concentration is equal to or less than 1 %. For the greatest accuracy, when a series of determinations on the same meat is performed, determine and use t
35、he endpoint from the titration curve (8.3) of that meat rather than using the endpoint obtained with sodium chloride standard solutions. 8.5 Blank test Carry out a blank test, in accordance with 8.2.2 to8.4 inclusive, substituting the water (4.1) for the sample suspension in 8.2.2. 9 Calculation Cal
36、culate the chloride content of the sample from the following equation: where Report the result to the nearest 0,1 % (m/m). w Cl is the chloride content of the sample, expressed as sodium chloride as a percentage by mass; V 1 is the volume, in millilitres, of the silver nitrate solution (4.3) used in
37、 the determination (8.4); V 2 is the volume, in millilitres, of the silver nitrate solution (4.3) used in the blank test(8.5); c is the concentration, in moles per litre, of the silver nitrate solution (4.3); m 1 is the mass, in grams, of the test solution(8.2.2); m is the mass, in grams, of the tes
38、t portion; w Cl V 1 V 2 ()c 50 5844 , m 1 m - =BS4401-16:1996 BSI 11-1998 3 10 Precision The precision of the method has been established by an interlaboratory test (see reference 5), carried out in accordance with ISO 5725. For the values obtained for the repeatability limit, r, and the reproducibi
39、lity limit, R, a probability level of 95 % holds. 10.1 Repeatability The absolute difference between two independent 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, sh
40、ould not be greater than the repeatability limit r as calculated using the following equation: whereis the mean of both results, as a percentage by mass. 10.2 Reproducibility The absolute difference between two single test results, obtained using the same method on identical test material in differe
41、nt laboratories with different operators using different equipment, should not be greater than the reproducibility limit R as calculated by the following equation: whereis the mean of both results, as a percentage by mass. 11 Test report The test report shall specify: the method in accordance with w
42、hich sampling was carried out, if known; the method used; the test result(s) obtained; and if the repeatability has been checked, the final quoted result obtained. It shall also mention all operating details not specified in this part of ISO 1841, or regarded as optional, together with details of an
43、y incidents which may have influenced the test result(s). The test report shall include all information necessary for the complete identification of the sample. r 0,0020,033w Cl + = w Cl R 0,0050,066w Cl + = w ClBS4401-16:1996 4 BSI 11-1998 Annex A (informative) Bibliography 1 ISO 3100-1:1991, Meat
44、and meat products Sampling and preparation of test samples Part1:Sampling. 2 ISO 5725:1986, Precision of test methods Determination of repeatability and reproducibility for a standard test method by inter-laboratory tests (now withdrawn) was used to obtain the precision results. 3 Codex Alimentarius
45、 Committee FAO/WHO. Report of the 9th Session of the Codex Committee on Methods of Analysis and Sampling. Determination of Total Chlorides, Potentiometric Method, Appendix II. Food and Agricultural Organization of the United Nations, 1975, Rome, Italy. 4 BRAMMELL, W.S., Collaborative study of a pote
46、ntiometric titration method for determining sodium chloride in foods. J. Assoc. Off. Anal. Chem., 57, 1974, pp. 1209-1216. 5 BELJAARS, P.R and HORWITZ, W., Comparison of the Volhard and potentiometric methods for the determination of chloride in meat products: Collaborative study. J. Assoc. Off. Ana
47、l. Chem., 68, 1985, pp.480-484.BS4401-16:1996 BSI 11-1998 List of references See national foreword.BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
48、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BSI British Standards Institution BSI is the independent national body responsible for preparing British Standards. It presents the UK view on standards in Europe and at the international level. It is incor
49、porated by Royal Charter. Revisions British Standards are updated by amendment or revision. Users of British Standards should make sure that they possess the latest amendments or editions. It is the constant aim of BSI to improve the quality of our products and services. We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would inform the Secretary of the technical committee responsible, the identity
