1、BRITISH STANDARD BS7319-12: 1990 Incorporating Amendment No.1 Analysis of sodiumchloride forindustrialuse Part12: Methods for determination of anti-caking additives content of salt for food useBS7319-12:1990 This BritishStandard, having been prepared under the directionof the Chemicals Standards Pol
2、icy Committee, waspublished under the authorityof the Board of BSI andcomes into effecton 30September1990 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference FAC/23 Draft for comment88/55625DC ISBN 0 580 18545 1 Committees responsible for this BritishSta
3、ndard The preparation of this BritishStandard was entrusted by the Chemicals Standards Policy Committee (FAC/-) to Technical Committee FAC/23, upon which the following bodies were represented: AFRC Institute of Food Research Chemical Industries Association Creamery Proprietors Association Department
4、 of Trade and Industry (Laboratory of the Government Chemist) Food and Drink Federation Milk Marketing Board for Northern Ireland Royal Association of British Dairy Farmers Salt Manufacturers Association Amendments issued since publication Amd. No. Date Comments 7786 June 1993 Indicated by a sidelin
5、e in the marginBS7319-12:1990 BSI 12-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Principle 1 3 Reagents 1 4 Apparatus 1 5 Procedure 1 6 Expression of results 2 7 Precision 2 Table 1 Mass of potassium hexacyanoferrate instandard solutions 2 Publication(s) re
6、ferred to Inside back coverBS7319-12:1990 ii BSI 12-1999 Foreword BS7319 has been prepared under the direction of the Chemicals Standards Policy Committee, at the request of Technical Committee FAC/23, Salt, primarily to provide appropriate methods for determination of vacuum salt for food use as sp
7、ecified in BS998:1990. The methods for determination were previously published as appendices to BS998:1969. This Part of BS7319 has been produced under the direction of the Food and Agriculture Standards Policy Committee. It is based upon a method developed on behalf of the European Committee for th
8、e Study of Salt. It supersedes Appendix Q of BS998:1969 which is withdrawn. A list of the Parts of BS7319 is given in Part1. 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
9、 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 back cover. This standard has been updated (see copyright date) and may have had am
10、endments incorporated. This will be indicated in the amendment table on the inside front cover.BS7319-12:1990 BSI 12-1999 1 1 Scope This Part of BS7319 specifies two methods for the determination of water-soluble hexacyanoferrate(II) (anti-caking additives) in salt for food use. The two methods are
11、applicable to products having levels of hexacyanoferrate(II), as follows. a) Direct method. For2.5mg to40mg of hexacyanoferrate(II) per kilogram of salt. b) Filtration method. For0.25mg to4mg of hexacyanoferrate(II) per kilogram of salt. NOTEThe titles of the publications referred to in this Part of
12、 this BritishStandard are listed on the inside back cover. 2 Principle The principles of this Part of BS7319 are as follows. a) Hexacyanoferrate(II) with iron(II), in acid solution forms the complex iron(II) hexacyanoferrate(II) which, in the presence of iron(III), oxidizes immediately to Prussian b
13、lue. The absorbance of this complex is determined at the wavelength of maximum absorbance, (approximately700nm). b) For the lower levels of potassium hexacyanoferrate(II) the Prussian blue is filtered on a membrane filter. After re-dissolving it in potassium hydroxide solution, the Prussian blue is
14、reformed in a much reduced volume. NOTE 1Hexacyanoferrate(III) is determined simultaneously. NOTE 2The intensity of the colour depends on the amount of alkali metal ions present in the solution. 3 Reagents 3.1 General. Use only reagents of recognized analytical grade and water complying with grade3
15、of BS3978. 3.2 Sulphuric acid, standard volumetric solution, c(“H 2 SO 4 )=1.0mol/L exactly. 3.3 Potassium hydroxide, standard volumetric solution, c(KOH)=0.05mol/L exactly. 3.4 Sodium chloride, hexacyanoferrate-free 3.5 Iron(II)/Iron(III) solution. Dissolve in water, in a 1000mL one-mark volumetric
16、 flask,200g of ammonium iron(II) sulphate hexahydrate, (NH 4 ) 2 SO 4 .FeSO 4 .6H 2 O, and25g of hydrated ammonium iron(III) sulphate, (NH 4 ) 2 SO 4 .Fe 2 (SO 4 ) 3 .24H 2 O. Add100mL of the sulphuric acid solution(3.2). Dilute to the mark with water and mix well. Filter the solution and store in a
17、 dark bottle. 3.6 Potassium hexacyanoferrate(II) stock solution, containing1mg/mL of potassium hexacyanoferrate. Dissolve in water, in a1000mL one-mark volumetric flask1.000g of potassium hexacyanoferrate(II) trihydrate, K 4 Fe(CN) 6 .3H 2 O. Add5mL of the potassium hydroxide solution(3.3). Dilute t
18、o the mark with water and mix well. Store this stock solution in a dark bottle for a maximum of1month. 3.7 Potassium hexacyanoferrate(II) standard solution, containing50g/mL of K 4 Fe(CN) 6 .3H 2 O. Take50.0mL of the stock solution(3.6) and transfer to a1000mL one-mark volumetric flask. Add5mL of th
19、e potassium hydroxide solution(3.3). Dilute to the mark with water and mix well. Prepare this solution at the time of use. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Spectrometer, or photometer, fitted with filters having a maximum transmission between690nm and710nm. 4.3 Membrane filter, of a
20、pproximately50mm diameter and pore size maximum of0.3m. 5 Procedure 5.1 Test portion Weigh, to the nearest0.1g, a test portion of approximately100g. 5.2 Blank test At the same time as the determination carry out a blank test, following the same procedure and using the same quantities of reagents and
21、 the same quantity of the sodium chloride(3.4), but omitting the test portion. 5.3 Preparation of the calibration curve 5.3.1 Preparation of standard colorimetric solutions Into a series of five100mL one-mark volumetric flasks, introduce10.0g of the sodium chloride(3.4) and the volumes of the potass
22、ium hexacyanoferrate(II) solution(3.7) as shown in Table 1. Dilute the solutions to approximately50mL with water, swirl until the crystals are dissolved and then add10.0mL of the potassium hydroxide solution(3.3). Add, in the order given,5mL of the sulphuric acid solution(3.2) and5mL of the iron(II)
23、/iron(III) solution(3.5). Mix the solution after each addition. Dilute to the mark with water and mix well.BS7319-12:1990 2 BSI 12-1999 Table 1 Mass of potassium hexacyanoferrate in standard solutions 5.3.2 Photometric measurements Adjust the apparatus to zero absorbance with respect to water prior
24、to each measurement. Measure the absorbance of each solution, using either the spectrometer at the wavelength of maximum absorbance (approximately700nm) or the photometer(4.1), fitted with the filters specified. Deduct the absorbance of the zero standard from the absorbance obtained for each standar
25、d colorimetric solution (see5.3.1). 5.3.3 Plotting the calibration curve Plot a graph having, for example, the masses of K 4 Fe(CN) 6 .3H 2 O contained in100mL of the standard colorimetric solutions (see5.3.1), expressed in micrograms, as abscissae, and the corresponding values of absorbance as ordi
26、nates. Prepare a new calibration curve whenever a new stock solution(3.6) is prepared. 5.4 Determination 5.4.1 Preparation of the test solution 5.4.1.1 Direct method (see clause1) Add the test portion (see5.1) to a500mL one-mark volumetric flask. Dissolve in water, dilute to the mark with water and
27、mix well. Take50.0mL of this solution and place in a100mL one-mark volumetric flask. Add10mL of the potassium hydroxide solution(3.3). Follow the procedure described in5.4.2. 5.4.1.2 Filtration method Transfer the test portion (see5.1) to a600mL beaker, dissolve in450mL of water and add10mL of the s
28、ulphuric acid solution(3.2) and25mL of the iron(II)/iron(III) solution(3.5). Mix the solution after each addition. Allow it to stand for15min. Filter the precipitate under vacuum on the membrane filter(4.3). Wash twice with15mL portions of water. Place the filter in10mL of the potassium hydroxide so
29、lution(3.3) and dissolve the precipitate. Transfer the solution quantitatively to a100mL one-mark volumetric flask and add to it10.0g of the sodium chloride(3.4). Dilute the solution to approximately60mL with water, swirl until the crystals are dissolved. Follow the procedure described in5.4.2. 5.4.
30、2 Determination Add, in the order given,5mL of the sulphuric acid solution(3.2) and5mL of the iron(II)/iron(III) solution(3.5). Mix after each addition. Dilute to the mark with water and mix well. Allow the solution to stand for15min. Adjust the apparatus to zero absorbance with respect to water pri
31、or to each measurement. Measure the absorbance of the solution, using either the spectrometer set at the wavelength of maximum absorbance (approximately700nm) or the photometer(4.2) fitted with the filters specified. 6 Expression of results Using the calibration curve (see5.3.3), determine the masse
32、s, in micrograms, of potassium hexacyanoferrate in the test solution and in the blank solution corresponding to the absorbance of the test solution. Calculate the water-soluble hexacyanoferrate(II) content, expressed as milligrams per kilogram of hexacyanoferrate Fe(CN) 6on a moisture free basis, us
33、ing one of the following expressions, as appropriate. a) Direct method b) Filtration method 7 Precision Comparative analyses on two samples carried out by11laboratories, have given the following statistical information. Volume of the standard solution(3.7) Corresponding mass of K 4 Fe(CN) 6 .3H 2 O
34、mL 0 a 2 5 10 15 g 0 100 250 500 750 a Zero standard. where m 1 is the mass of potassium hexacyanoferrate found in the test solution (ing) (see5.4.2); m 2 is the mass of potassium hexacyanoferrate found in the blank test solution(5.2) (ing); m 0 is the mass of the test portion (ing); H is the moistu
35、re content determined in accordance with BS7319-2 in% (m/m). Mean (mg/kg) 3.09 Standard deviation for repeatability (r) 0.083 Standard deviation for reproducibility (R) 0.536 m 1 m 2 m 0 - 500 50 - 100 100H () - 211.96 422.39 - m 1 m 2 m 0 - 100 100H () - 211.96 422.39 - BS7319-12:1990 BSI 12-1999 P
36、ublication(s) referred to BS998, Specification for vacuum salt for food use 1) . BS3978, Specification for water for laboratory use. BS7319, Analysis of sodium chloride for industrial use. BS7319-1, Method for determination of sodium chloride content. BS7319-2, Method for determination of moisture c
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