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1、BRITISH STANDARD BS 7319-12: 1990 Incorporating Amendment No. 1 Analysis of sodium chloride for industrial use Part 12: Methods for determination of anti-caking additives content of salt for food use Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:32:59 GMT+0
2、0:00 2006, Uncontrolled Copy, (c) BSI BS 7319-12:1990 This British Standard, having been prepared under the direction of the Chemicals Standards Policy Committee, was published under the authority of the Board of BSI and comes into effect on 30 September 1990 BSI 12-1999 The following BSI references
3、 relate to the work on this standard: Committee reference FAC/23 Draft for comment 88/55625 DC ISBN 0 580 18545 1 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Chemicals Standards Policy Committee (FAC/-) to Technical Committee FAC/23,
4、 upon which the following bodies were represented: AFRC Institute of Food Research Chemical Industries Association Creamery Proprietors Association Department of Trade and Industry (Laboratory of the Government Chemist) Food and Drink Federation Milk Marketing Board for Northern Ireland Royal Associ
5、ation of British Dairy Farmers Salt Manufacturers Association Amendments issued since publication Amd. No.DateComments 7786June 1993Indicated by a sideline in the margin Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:32:59 GMT+00:00 2006, Uncontrolled Copy,
6、(c) BSI BS 7319-12:1990 BSI 12-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Principle1 3Reagents1 4Apparatus1 5Procedure1 6Expression of results2 7Precision2 Table 1 Mass of potassium hexacyanoferrate in standard solutions2 Publication(s) referred toInside back co
7、ver Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:32:59 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7319-12:1990 ii BSI 12-1999 Foreword BS 7319 has been prepared under the direction of the Chemicals Standards Policy Committee, at the request of Technical
8、 Committee FAC/23, Salt, primarily to provide appropriate methods for determination of vacuum salt for food use as specified in BS 998:1990. The methods for determination were previously published as appendices to BS 998:1969. This Part of BS 7319 has been produced under the direction of the Food an
9、d Agriculture Standards Policy Committee. It is based upon a method developed on behalf of the European Committee for the Study of Salt. It supersedes Appendix Q of BS 998:1969 which is withdrawn. A list of the Parts of BS 7319 is given in Part 1. A British Standard does not purport to include all t
10、he 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 of pages This document comprises a front cover, an inside front cover, pages i and ii
11、, pages 1 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 cover. Licensed Copy: London South Bank University, London South Bank University, Fr
12、i Dec 08 13:32:59 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7319-12:1990 BSI 12-19991 1 Scope This Part of BS 7319 specifies two methods for the determination of water-soluble hexacyanoferrate (II) (anti-caking additives) in salt for food use. The two methods are applicable to products having le
13、vels of hexacyanoferrate (II), as follows. a) Direct method. For 2.5 mg to 40 mg of hexacyanoferrate (II) per kilogram of salt. b) Filtration method. For 0.25 mg to 4 mg of hexacyanoferrate (II) per kilogram of salt. NOTEThe titles of the publications referred to in this Part of this British Standar
14、d are listed on the inside back cover. 2 Principle The principles of this Part of BS 7319 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 blue. The absor
15、bance of this complex is determined at the wavelength of maximum absorbance, (approximately 700 nm). 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 reformed in
16、 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 grade 3 of BS 397
17、8. 3.2 Sulphuric acid, standard volumetric solution, c(“H2SO4) = 1.0 mol/L exactly. 3.3 Potassium hydroxide, standard volumetric solution, c(KOH) = 0.05 mol/L exactly. 3.4 Sodium chloride, hexacyanoferrate-free 3.5 Iron (II)/Iron (III) solution. Dissolve in water, in a 1 000 mL one-mark volumetric f
18、lask, 200 g of ammonium iron (II) sulphate hexahydrate, (NH4)2SO4.FeSO4.6H2O, and 25 g of hydrated ammonium iron (III) sulphate, (NH4)2SO4.Fe2(SO4)3.24H2O. Add 100 mL of the sulphuric acid solution (3.2). Dilute to the mark with water and mix well. Filter the solution and store in a dark bottle. 3.6
19、 Potassium hexacyanoferrate (II) stock solution, containing 1 mg/mL of potassium hexacyanoferrate. Dissolve in water, in a 1 000 mL one-mark volumetric flask 1.000 g of potassium hexacyanoferrate (II) trihydrate, K4Fe(CN)6.3H2O. Add 5 mL of the potassium hydroxide solution (3.3). Dilute to the mark
20、with water and mix well. Store this stock solution in a dark bottle for a maximum of 1 month. 3.7 Potassium hexacyanoferrate (II) standard solution, containing 50 g/mL of K4Fe(CN)6.3H2O. Take 50.0 mL of the stock solution (3.6) and transfer to a 1 000 mL one-mark volumetric flask. Add 5 mL of the po
21、tassium 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 between 690 nm and 710 nm. 4.3 Membrane filter, of
22、approximately 50 mm diameter and pore size maximum of 0.3 m. 5 Procedure 5.1 Test portion Weigh, to the nearest 0.1 g, a test portion of approximately 100 g. 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 rea
23、gents and 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 five 100 mL one-mark volumetric flasks, introduce 10.0 g of the sodium chloride (3.4) and the volume
24、s of the potassium hexacyanoferrate (II) solution (3.7) as shown in Table 1. Dilute the solutions to approximately 50 mL with water, swirl until the crystals are dissolved and then add 10.0 mL of the potassium hydroxide solution (3.3). Add, in the order given, 5 mL of the sulphuric acid solution (3.
25、2) and 5 mL of the iron (II)/iron (III) solution (3.5). Mix the solution after each addition. Dilute to the mark with water and mix well. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:32:59 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7319-12:1990 2 BSI 12
26、-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 to each measurement. Measure the absorbance of each solution, using either the spectrometer at the wavelength of maximum absorbanc
27、e (approximately 700 nm) or the photometer (4.1), fitted with the filters specified. Deduct the absorbance of the zero standard from the absorbance obtained for each standard colorimetric solution (see 5.3.1). 5.3.3 Plotting the calibration curve Plot a graph having, for example, the masses of K4Fe(
28、CN)6.3H2O contained in 100 mL of the standard colorimetric solutions (see 5.3.1), expressed in micrograms, as abscissae, and the corresponding values of absorbance as ordinates. Prepare a new calibration curve whenever a new stock solution (3.6) is prepared. 5.4 Determination 5.4.1 Preparation of th
29、e test solution 5.4.1.1 Direct method (see clause 1) Add the test portion (see 5.1) to a 500 mL one-mark volumetric flask. Dissolve in water, dilute to the mark with water and mix well. Take 50.0 mL of this solution and place in a 100 mL one-mark volumetric flask. Add 10 mL of the potassium hydroxid
30、e solution (3.3). Follow the procedure described in 5.4.2. 5.4.1.2 Filtration method Transfer the test portion (see 5.1) to a 600 mL beaker, dissolve in 450 mL of water and add 10 mL of the sulphuric acid solution (3.2) and 25 mL of the iron (II)/iron (III) solution (3.5). Mix the solution after eac
31、h addition. Allow it to stand for 15 min. Filter the precipitate under vacuum on the membrane filter (4.3). Wash twice with 15 mL portions of water. Place the filter in 10 mL of the potassium hydroxide solution (3.3) and dissolve the precipitate. Transfer the solution quantitatively to a 100 mL one-
32、mark volumetric flask and add to it 10.0 g of the sodium chloride (3.4). Dilute the solution to approximately 60 mL with water, swirl until the crystals are dissolved. Follow the procedure described in 5.4.2. 5.4.2 Determination Add, in the order given, 5 mL of the sulphuric acid solution (3.2) and
33、5 mL 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 for 15 min. Adjust the apparatus to zero absorbance with respect to water prior to each measurement. Measure the absorbance of the solution, using either
34、the spectrometer set at the wavelength of maximum absorbance (approximately 700 nm) or the photometer (4.2) fitted with the filters specified. 6 Expression of results Using the calibration curve (see 5.3.3), determine the masses, in micrograms, of potassium hexacyanoferrate in the test solution and
35、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)6 on a moisture free basis, using one of the following expressions, as appropriate. a) Direct method b
36、) Filtration method 7 Precision Comparative analyses on two samples carried out by 11 laboratories, have given the following statistical information. Volume of the standard solution (3.7) Corresponding mass of K4Fe(CN)6.3H2O mL 0a 2 5 10 15 g 0 100 250 500 750 a Zero standard. where m1is the mass of
37、 potassium hexacyanoferrate found in the test solution (in g) (see 5.4.2); m2is the mass of potassium hexacyanoferrate found in the blank test solution (5.2) (in g); m0is the mass of the test portion (in g); His the moisture content determined in accordance with BS 7319-2 in % (m/m). Mean (mg/kg)3.0
38、9 Standard deviation for repeatability (r)0.083 Standard deviation for reproducibility (R) 0.536 m1m2 m0 - 500 50 - - 100 100H() - - 211.96 422.39 - - m1m2 m0 - 100 100H() - - 211.96 422.39 - - Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:32:59 GMT+00:00 2
39、006, Uncontrolled Copy, (c) BSI BS 7319-12:1990 BSI 12-1999 Publication(s) referred to BS 998, Specification for vacuum salt for food use1). BS 3978, Specification for water for laboratory use. BS 7319, Analysis of sodium chloride for industrial use. BS 7319-1, Method for determination of sodium chl
40、oride content. BS 7319-2, Method for determination of moisture content. 1) Referred to in the foreword only. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:32:59 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7319-12: 1990 BSI 389 Chiswick High Road London W4
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