BS 4427-11-1983 Methods of test for sodium tripolyphosphate (pentasodium triphosphate) and sodium pyrophosphate (tetrasodium pyrophosphate) for industrial use - Separation by colum.pdf

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1、BRITISH STANDARD BS 4427-11: 1983 Methods of test for Sodium tripolyphosphate (pentasodium triphosphate) and sodium pyrophosphate (tetrasodium pyrophosphate) for industrial use Part 11: Separation by column chromatography and determination of the different phosphate forms UDC 661.833.456+661.833.458

2、:543.544.42.062:546.185BS4427-11:1983 This British Standard, having been prepared under the directionof the Chemical Standards Committee, was published under the authority ofthe Board of BSI on 28 February1983 BSI 11-1999 First edition July1976 First revision February1983 The following BSI reference

3、s relate to the work on this standard: Committee reference CIC/25 Draft (reference 82/52542) announced in BSINews December1982 ISBN 0 580 13079 7 Cooperating organizations The Chemicals Standards Committee, under whose direction this British Standard was prepared, consists of representatives from th

4、e following Government departments and scientific and industrial organizations: Association of Fatty Acid Distillers British Tar Industry Association Chemical Industries Association* Chemical Society, Analytical Division Consumer Standards Advisory Committee of BSI Department of Health and Social Se

5、curity Department of Industry (Laboratory of the Government Chemist)* Fertiliser Manufacturers Association Ltd.* Hydrocarbon Solvents Association Ministry of Agriculture, Fisheries and Food Ministry of Defence National Sulphuric Acid Association Paintmakers Association of Great Britain Ltd. Royal In

6、stitute of Public Health and Hygiene Soap and Detergent Industry Association Standardization of Tar Products Tests Committee The organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this Bri

7、tish Standard: Campden Food Preservation Research Association Flour Milling and Baking Research Association Institute of Metal Finishing Institution of Water Engineers and Scientists National Association of Soft Drinks Manufacturers Society of Chemical Industry Textile Institute Amendments issued si

8、nce publication Amd. No. Date of issue CommentsBS4427-11:1983 BSI 11-1999 i Contents Page Cooperating organizations Inside front cover Foreword ii 1 Scope 1 2 Principle 1 3 Reagents 1 4 Apparatus 1 5 Procedure 1 6 Expression of results 3 7 Test report 3 Appendix A Determination of phosphorus(V) oxid

9、e in the eluates obtainedbychromatographic separation on a column 7 Figure 1 Ion-exchange column with dropping funnel 4 Figure 2 Ion-exchange column with typical syphon device 5 Figure 3 Typical graph obtained during the determination oftheelutionconditions 6 Table 1 Concentrations of standard match

10、ing solutions andcorrespondingoptical path lengths of cells 7 Publications referred to Inside back coverBS4427-11:1983 ii BSI 11-1999 Foreword This British Standard has been prepared under the direction of the Chemicals Standards Committee in order to provide methods for the analysis of sodium tripo

11、lyphosphate and sodium pyrophosphate. For some years the UK has participated in the work of preparing methods of test applicable to sodium tripolyphosphate and sodium pyrophosphate for industrial use, organized by subcommittee6 (formerly working group7) “Phosphoric acid and condensed phosphates” of

12、Technical Committee47 “Chemistry” of the International Organization for Standardization (ISO). As international agreement is reached on the methods, it is proposed to publish them as Parts of this British Standard. This Part of BS4427 is based on ISO3358:1979 “Sodium tripolyphosphate and sodium pyro

13、phosphate for industrial use Separation by column chromatography and determination of the different phosphate forms”. It is a revision of the1979 edition of BS4427-11, which was identical with the first(1976) edition of ISO3358. BS4427-11:1979 is now withdrawn. Experimental work carried out since th

14、e first edition of ISO3358 has shown that the method described therein was specific only for ortho-, pyro- and tripolyphosphates, and that trimetaphosphate was not eluted quantitatively in all cases with the0.75M potassium chloride solution specified for that purpose, although it was eluted together

15、 with all other higher condensed phosphates by the final elution with2M hydrochloric acid solution. The revision of the1979 edition of ISO3358 reflects this fact and also replaces the non-SI “unit” molarity used for expressing the concentrations of reagents by mass concentrations, although the corre

16、sponding concentrations in terms of molarities are given in footnotes. This revision of BS4427-11 differs from ISO3358:1979 in the following respects which remove features of the International Standard that were unacceptable to the UK (although it was approved by the UK): a) deletion of a suction de

17、vice to introduce the solutions into the chromatographic column; b) substitution of a revised typical diagram (Figure 3) obtained during determination of the elution conditions, that corrects the misleading implication that the higher condensed phosphates are eluted by5mL of hydrochloric acid soluti

18、on. In addition, some errors in the text of the International Standard have been corrected. These changes and corrections have been notified to ISO for consideration in a future revision of ISO3358. This standard describes methods of test only and should not be used or quoted as a specification defi

19、ning limits of purity. References to the standard should indicate that the methods of test used conform to the requirements of BS4427. 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.

20、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, pages1 to8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may

21、have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS4427-11:1983 BSI 11-1999 1 1 Scope This Part of BS4427 describes a method for the separation and the determination of the different phosphate forms in sodium tripolyphosphate (pentasodium trip

22、hosphate) and sodium pyrophosphate (tetrasodium diphosphate) for industrial use. The procedure specified allows the selective determinations of orthophosphate (Na 2 HPO 4 ), of pyrophosphate (Na 4 P 2 O 7 ) and of tripolyphosphate (Na 5 P 3 O 10 ), and also the evaluation of the total content of mor

23、e condensed forms of phosphates in the absence of tetrametaphosphates and pentametaphosphates. NOTE 1In practice, tetrametaphosphates and pentametaphosphates are not usually present in commercial tripolyphosphates and pyrophosphates. NOTE 2Although the procedure can separate orthophosphate, its dete

24、rmination is not possible if the content is lower than0.1%(m/m); in this case its determination should be carried out by the method specified in BS4427-8. NOTE 3The titles of the publications referred to in this Part of this British Standard are listed on the inside back cover. 2 Principle The phosp

25、hate anions in a test portion are absorbed on to an anionic ion-exchange resin and eluted with potassium chloride solutions of increasing concentrations and finally with hydrochloric acid solution. The contents of P 2 O 5in the different eluate volumes (containing the different phosphate forms) are

26、then determined. 3 Reagents 3.1 General. During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity complying with the requirements of BS3978, free from silica. 3.2 Ion-exchange resin, strongly basic anionic type, in the chloride form

27、, particle size between0.07mm and0.16mm. NOTEThe resins commercially available as Biorad AG1 8 or Dowex1 8, purified and graded, meet these requirements and have given satisfactory results. 3.3 Hydrochloric acid, approximately73g/L 1)solution of HCl. 3.4 Buffer solution, pH4.3. Dissolve51g of sodium

28、 acetate trihydrate (CH 3 COONa.3H 2 O) and46mL of glacial acetic acid, approximately1.05g/mL, in water. Add several milligrams of phenylmercury(II) acetate (C 6 H 5 HgOOCCH 3 ) and dilute to1000mL. 3.5 Potassium chloride, approximately18.5g/L 2)solution of KCl. Dissolve18.5g of KCl in water, add10m

29、L of the buffer solution(3.4) and several milligrams of polymercury (II) acetate to1L. 3.6 Potassium chloride, approximately37g/L 3)solution of KCl. Dissolve37g of KCl in water, add10mL of the buffer solution(3.4) and several milligrams of polymercury (II) acetate and dilute to1L. 4 Apparatus Ordina

30、ry laboratory apparatus is required together with the following. 4.1 Ion-exchange column consisting of a glass tube300mm long and with an internal diameter of12mm. The top of the tube is fitted with a ground glass socket enabling a100mL graduated cylindrical dropping funnel to be fitted (seeFigure 1

31、). The bottom of the tube is extended by a narrower glass tube approximately90mm long and8mm in diameter, fitted at its middle with a stopcock, the end of which is drawn out to a jet. The bottom of the ion-exchange column is fitted with a silica wool pad about10mm thick or, preferably, a fritted gla

32、ss disk of porosity P100 (pore diameter of between404m and1004m). NOTEThe solutions can also be introduced into the column using a syphon as illustrated in Figure 2. 5 Procedure 5.1 Preparation of the ion-exchange column. Wash approximately20g of the resin(3.2) with a jet of water on a634m sieve (se

33、e BS410) to remove fine particles. Transfer the residue on the sieve to a ground-glass filter, porosity P40 (pore diameter between164m and404m) and remove most of the water by suction. After this preliminary preparation, allow the resin to stand for about12h in100mL of the hydrochloric acid solution

34、(3.3);18g of the resin are required. Introduce the resin into the ion-exchange column(3.2)(18g occupies a height of approximately240mm) and wash with water until the pH of the effluent is between4.5 and5. During the analysis, maintain the liquid level at all times several millimetres above the top o

35、f the column of resin. 1) Previously2M. 2) Previously0.25M. 3) Previously0.50M.BS4427-11:1983 2 BSI 11-1999 5.2 Test portion and preparation of the test solution. Place0.500g, weighed to the nearest0.0001g, of the test sample in a250mL one-mark volumetric flask. Dissolve it in water, add5mL of the b

36、uffer solution(3.4), dilute to the mark and mix. Filter the solution if it is turbid. 5.3 Preliminary test 5.3.1 General. The conditions under which the elution of phosphates is carried out depend on the particle size distribution of the ion-exchange resin. The separation can, moreover, be influence

37、d by the presence of foreign salts in the product examined. For this reason it is recommended that a preliminary test be carried out on the test solution(5.2) to determine the conditions to be observed during the chromatographic separation. In addition, this test provides confirmation that the produ

38、ct is “normal” and that it can be analysed by the procedure described in this British Standard. 5.3.2 Determination of the elution conditions. Immediately after preparation, place10.0mL of the test solution(5.2) in the upper part of the column, on top of the ion-exchange resin. Apply a slight air pr

39、essure, controlled by means of the pressure regulator, and open the stopcock so as to allow the solution to penetrate into the resin. Close the stopcock before the solution has completely run through so that several millimetres of solution remain above the resin surface. Carefully wash the inner wal

40、ls of the column above the resin surface with about5mL of water and re-open the stopcock to allow the washings to enter the resin. Close the stopcock before all the liquid has penetrated into the resin. Pass through the column, from the graduated cylindrical dropping funnel, about110mL of the potass

41、ium chloride solution(3.5), controlling the flow at a constant rate of about2.5mL/min to3mL/min (obtained by application of pressure, controlled by the regulator), and collect the eluate in fractions of5mL. Determine the P 2 O 5content of each fraction (see5.6 and Appendix A) so as to establish whic

42、h contain orthophosphate and pyrophosphate respectively, when eluted in that order. Then carry out the same procedure, running about80mL of the potassium chloride solution(3.6) through the column, to elute the tripolyphosphate. Plot a graph (seeFigure 3 for a typical graph) having the successive5mL

43、fractions as absciassae and the corresponding contents of P 2 O 5as ordinates. Determine from this graph the minimum volumes of the potassium chloride solutions which should be used to effect the separation. 5.4 Regeneration of the column. At the end of the preliminary test, check that several milli

44、metres of potassium chloride solution remain above the resin surface, pass about200mL of the hydrochloric acid solution(3.3) through the column and allow the column to stand under acid conditions for about12h. Wash the column, first by running through about50mL of the hydrochloric acid solution(3.3)

45、 and then by running through50mL of water. Add more water so as to fill the column completely. Stopper the column and invert it to suspend the resin in the water. Return the column to the upright position, allow the resin to settle and pass water through the resin until the pH of the effluent is bet

46、ween4.5 and5. 5.5 Separation procedure. Carry out the procedure described in5.3.2, using10.0mL of the test solution(5.2) prepared immediately beforehand and using the volumes of the different potassium chloride solutions determined as in5.3.2. Collect separately the three eluate volumes correspondin

47、g to each of the three phosphate forms (orthopolyphosphates, pyropolyphosphates and tripolyphosphates). Before changing from one eluate volume to the next, collect two or three5mL fractions and check the P 2 O 5content according to the method described in Appendix A to verify that the separation is

48、satisfactory. The intermediate fractions should contain only negligible quantities ofP 2 O 5 . Otherwise the test should be repeated. After collection of the last eluate volume, regenerate the column, following the procedure specified in5.4, retaining the eluate obtained by passing the200mL of the h

49、ydrochloric acid solution(3.3). This will contain any higher condensed forms of phosphate that may be present. 5.6 Determination of phosphorus(V) oxide in the eluates 5.6.1 For the analysis of the 5mL fractions collected during the preliminary test. Use the reduced molybdophosphate photometric method specified in Appendix A. 5.6.2 For the analysis of sodium tripolyphosphate. Determine the phosphorus(V) oxide in the eluate volume corresponding to the orthophosphate and in that corresponding to the pyrophosphate using the reduced molybdophosphate photometric method