1、BRITISH STANDARD BS 4401-6:1996 ISO 1841-1:1996 Methods of test for Meat and meat products Part 6: Determination of chloride content (Volhard method) ICS 67.120.10BS4401-6:1996 This British Standard, having been prepared under the direction of the Consumer Products and Services Sector Board, was pub
2、lished under the authority of the Standards Board and comes into effect on 15September1996 BSI 11-1998 First published November 1970 Second edition October 1981 Third edition 1996 The following BSI references relate to the work on this standard: Committee reference AW/6 Draft for comment 94/504478 D
3、C ISBN 0 580 26068 2 Committees responsible for this British Standard 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 Manufac
4、turers Association British Poultry Meat Federation Ltd. Department 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 o
5、f Chemistry Worshipful Company of Butchers Amendments issued since publication Amd. No. Date CommentsBS4401-6:1996 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 o
6、f test sample 2 8 Procedure 2 9 Calculation 2 10 Precision 2 11 Test report 3 Annex A (informative) Bibliography 4 List of references Inside back coverBS4401-6:1996 ii BSI 11-1998 National foreword This Part of BS 4401 has been prepared by Technical Committee AW/6 and is identical with ISO1841-1:199
7、6 Meat and meat products Determination of chloride content Part1: Volhard method published by the International Organization for Standardization (ISO) and in the preparation of which the United Kingdom played a full part. It is a revision of BS 4401-6:1981 which is withdrawn and from which it differ
8、s in that precision data from an international collaborative trial has been included. A potentiometric method for the determination of chloride content in meat and meat products is given in BS4401-16. ISO 5725:1986, to which informative reference is made in the text, has been superseded by ISO 5725-
9、1:1994, ISO 5725-2:1994, ISO 5725-3:1994, ISO 5725-4:1994 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 definitions, BS ISO 5725-2:1994 Basic methods for the determination of repe
10、atability and reproducibility of a standard measurement method, BS ISO 5725-3:1994, Intermediate measures of the precision of a standard measurement method, BS ISO 5725-4:1994, Intermediate measures of the precision of a standard measurement method, BSISO5725-4:1994 Basic methods for the determinati
11、on of the trueness 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 Briti
12、sh Standard does not 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
13、 comprises a front cover, an inside front cover, pages i and ii, pages1 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 the inside front cover.BS4401-6:1996 BSI
14、 11-1998 1 1 Scope 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 than 1,0 % (m/m). 2 Definition For the purposes of this part of ISO 1841, the following definition
15、 applies. 2.1 chloride content of meat and meat products total chloride content determined by the method specified in this part of ISO1841. It is expressed as sodium chloride as a percentage by mass 3 Principle Extraction of a test portion with hot water and precipitation of the proteins. After filt
16、ration and acidification, addition of an excess of silver nitrate solution to the extract, and titration of this excess with potassium thiocyanate solution. 4 Reagents Use only reagents of recognized analytical grade unless otherwise specified. 4.1 Water, distilled and halogen-free. Halogen-free tes
17、t: Add 1ml of silver nitrate c(AgNO 3 ) 0,1 mol/l and 5ml of nitric acid c(HNO 3 ) 4mol/l to 100ml of water. No more than a slight turbidity shall be produced. 4.2 Nitrobenzene or nonan-1-ol. 4.3 Nitric acid, c(HNO 3 4 mol/l. Mix 1 volume of concentrated nitric acid (1,39g/ml # r 20# 1,42g/ml) with
18、3 volumes of water. 4.4 Solutions for precipitation of proteins 4.4.1 Reagent A Dissolve in water 106 g of potassium hexacyanoferrate(II) trihydrate K 4 Fe(CN) 6 3H 2 O. Transfer quantitatively to a 1000ml one-mark volumetric flask (5.2) and dilute to the mark with water. 4.4.2 Reagent B Dissolve in
19、 water 220 g of zinc acetate dihydrate Zn(CH 3 COO) 2 .2H 2 O and add 30ml of glacial acetic acid. Transfer quantitatively to a 1000ml one-mark volumetric flask (5.2) and dilute to the mark with water. 4.5 Silver nitrate, standard volumetric solution, c(AgNO 3 )=0,1mol/l. Dissolve in water 16,989 g
20、of silver nitrate, previously dried for 2h at 150C2C and allowed to cool in a desiccator. Transfer quantitatively to a1000ml one-mark volumetric flask (5.2) and dilute to the mark with water. Store this solution in a dark glass container out of direct sunlight 4.6 Potassium thiocyanate, standard vol
21、umetric solution, c(KSCN)=0,1mol/l. Dissolve in water about 9,7g of potassium thiocyanate. Transfer quantitatively to a 1000ml one-mark volumetric flask (5.2) and dilute to the mark with water. Standardize the solution to the nearest 0,0001mol/l against the silver nitrate solution (4.5) using the am
22、monium iron(III) sulfate solution (4.7) as indicator. 4.7 Ammonium iron(III) sulfate Prepare a saturated aqueous solution at room temperature from the dodecahydrate NH 4 Fe(SO 4 ) 2 12H 2 2O 5 Apparatus Usual laboratory apparatus and, in particular, the following. 5.1 Homogenizing equipment, mechani
23、cal 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 One-mark volumetric flasks, of capacity 1 000ml and 200ml. 5.3 Conical flasks, of capacity about 250ml. 5.4 Burette
24、, of capacity 25ml or 50ml. 5.5 One-mark pipettes, of capacity 20ml. 5.6 Boiling water bath. 5.7 Analytical balance, capable of weighing to an accuracy of 0,001g. 6 Sampling It is important that the laboratory receive a sample which is truly representative and has not been damaged or changed during
25、transport or storage. Sampling is not part of the method specified in this part of ISO1841. A recommended sampling method is given in ISO3100-1. Proceed from a representative sample of at least200g.BS4401-6:1996 2 BSI 11-1998 7 Preparation of test sample 7.1 Homogenize the laboratory sample with the
26、 appropriate equipment (5.1). Take care that the temperature of the sample material does not rise above 25C. If a mincer is used, pass the sample at least twice through the equipment. 7.2 Fill a suitable airtight container with the prepared sample. Close the container and store in such way that dete
27、rioration and change in composition are prevented. Analyse the sample as soon as practicable, but always within 24h of homogenization. 8 Procedure NOTE 1 If it is required to check whether the repeatability requirement is met, carry out two single determinations in accordance with8.1 to8.4 under rep
28、eatability conditions. 8.1 Test portion Weigh, to the nearest 0,001 g, about 10 g of the test sample and transfer it quantitatively to a conical flask (5.3). 8.2 Deproteination Add 100ml of hot water (4.1) to the test portion(8.1). Heat the flask and its contents for15min in the boiling water bath (
29、5.6). Periodically shake the contents of the flask. Allow the flask and its contents to cool to room temperature, then add successively 2ml of reagent A (4.4.1) and 2ml of reagent B (4.4.2). Mix thoroughly after each addition. Allow the flask to stand for 30 min at room temperature. Transfer the con
30、tents quantitatively to a 200ml volumetric flask (5.2) and dilute to the mark with water. Mix the contents thoroughly and filter through a fluted filter paper. NOTE 2If this method is used for the determination of the nitrate and nitrite content or if ascorbic acid is present in the sample in concen
31、trations higher than 0,1%, it is necessary to add also 0,5 g of activated charcoal to the test portion (8.1). After mixing reagents A and B, adjust the pH to between 7,5 and 8,3 by means of a sodium hydroxide solution. 8.3 Determination Transfer 20ml of the filtrate to a conical flask (5.3) by means
32、 of a pipette (5.5) and add, from a graduated measuring cylinder, 5ml of the dilute nitric acid (4.3) and 1ml of the ammonium iron(III) sulfate solution (4.7) as indicator. Transfer 20ml of the silver nitrate solution (4.5) to the conical flask by means of a pipette (5.5). Add3ml of the nitrobenzene
33、 or nonan-1-ol from a graduated measuring cylinder and mix thoroughly. Shake vigorously to coagulate the precipitate. Titrate the contents of the conical flask with the potassium thiocyanate (4.6) until the appearance of a persistent pink coloration. Record the volume of the potassium thiocyanate so
34、lution required, to the nearest 0,05ml. 8.4 Blank test Carry out a blank test, in accordance with8.2 and8.3, using the same volume of silver nitrate solution (4.5). 9 Calculation Calculate the chloride content of the sample from the following equation: where Report the result to the nearest 0,05% (m
35、/m). 10 Precision The precision of the method has been established by an interlaboratory test (see reference4), carried out in accordance with ISO5725. For the values obtained for the repeatability limit, r, and the reproducibility limit, R, a probability level of 95% holds. w Cl is the chloride con
36、tent of the sample, expressed as sodium chloride as a percentage by mass; V 1 is the volume, in millilitres, of the potassium thiocyanate solution (4.6) used in the determination (8.3); V 2 is the volume, in millilitres, of the potassium thiocyanate solution (4.6) used in the blank test (8.4); c is
37、the concentration of the potassium thiocyanate solution (4.6), in moles per litre; m is the mass, in grams, of the test portion. wCl 0,058 44V 2 V 1 () 200 20 - 100 m -c = 5844 , V 2 V 1 m -c =BS4401-6:1996 BSI 11-1998 3 10.1 Repeatability The absolute difference between two independent single test
38、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, should not be greater than 0,15% (m/m) for sodium chloride contents between 1,0% and 2,0%; 0,20% (m/m) for sodium chloride contents
39、 greater than 2,0%. 10.2 Reproducibility The absolute difference between two single test results, obtained using the same method on identical test material in different laboratories with different operators using different equipment, should not be greater than: 0,20% (m/m) for sodium chloride conten
40、ts between 1,0 and 2,0%; 0,30% (m/m) for sodium chloride contents greater than 2,0%. 11 Test report The test report shall specify: the method in accordance with which sampling was carried out, if known; the method used; the test result(s) obtained; and if the repeatability has been checked, the fina
41、l quoted result obtained. It shall also mention all operating details not specified in this part of ISO1841, or regarded as optional, together with details of any incidents which have influenced the test result(s). The test report shall include all information necessary for the complete identificati
42、on of the sample.BS4401-6:1996 4 BSI 11-1998 Annex A (informative) Bibliography 1 ISO 3100-1:1991, Meat 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
43、by inter-laboratory tests (now withdrawn) was used to obtain the precision data. 3 Amtliche Sammlung von Untersuchungsverfahren nach Par. 35 LMBG. Bestimmung des Kochsalzgehaltes in Fleisch und Fleischerzeugnissen. L06.00-5, September 1980. 4 BELJAARS, P.R and HORWITZ, W, Comparison of the Volhard a
44、nd potentiometric methods for the determination of chloride in meat products: Collaborative study. J. Assoc. Off. Anal. Chem., 68, 1985, pp.480-484.BS4401-6:1996 BSI 11-1998 List of references See national foreword.BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | |
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