BS 2782-4 Method 453C-1996 Methods of testing plastics - Chemical properties - Determination of residual acrylonitrile monomer content in styrene acrylonitrile copolymers using gas.pdf

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1、BRITISH STANDARD BS2782-4: Method453C: 1996 ISO4581:1994 Methods of testing Plastics Part4: Chemical properties Method453C: Determination of residual acrylonitrile monomer content in styrene/acrylonitrile copolymers using gas chromatography ICS 83.080.20BS2782-4:Method 453C:1996 This British Standar

2、d, having been prepared under the directionof the Sector Board forChemicals and Materials, waspublished under the authorityof the Standards Boardand comes into effect on 15January1996 BSI08-1999 The following BSI references relate to the work on this standard: Committee reference PRI/21 Draft for co

3、mment93/301675 DC ISBN 0 580 24979 4 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee PRI/21, Testing of plastics, upon which the following bodies were represented: The British Apparel and Textile Confederation British Pla

4、stics Federation Department of the Environment (Building Research Establishment) Department of Trade and Industry (National Physical Laboratory) Electrical and Electronic Insulation Association (BEAMA Ltd.) GAMBICA (BEAMA Ltd.) Institute of Materials Ministry of Defence Packaging and Industrial Film

5、s Association PIRA International RAPRA Technology Ltd. Royal Society of Chemistry Amendments issued since publication Amd. No. Date CommentsBS2782-4:Method 453C:1996 BSI 08-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Normative reference 1 3 Princip

6、le 1 4 Reagents 1 5 Apparatus 1 6 Preparation of test sample 2 7 Procedure 2 8 Expression of results 3 9 Test report 3 Annex A (normative) Method for determining contents lower than3ppm by means of headspace gas chromatography using a thermionic nitrogen detector 4 List of references Inside back cov

7、erBS2782-4:Method 453C:1996 ii BSI 08-1999 National foreword This method of BS2782-4 has been prepared by Technical Committee PRI/21, and is identical with ISO4581:1994 Plastics Styrene/acrylonitrile copolymers Determination of residual acrylonitrile monomer content Gas chromatography method. NOTEIn

8、ternational and European Standards, as well as overseas standards, are available from Customer Services, BSI,389Chiswick High Road, London, W44AL. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct a

9、pplication. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-reference International Standard Corresponding British Standard ISO2561:1974 BS2782 Methods of testing plastics Part4 Chemical properties Method453A:1978 Determination of residual styrene

10、monomer in polystyrene by gas chromatography (Identical) Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1to6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This w

11、ill be indicated in the amendment table on the inside front cover.BS2782-4:Method 453C:1996 BSI 08-1999 1 1 Scope This International Standard specifies a method for determining the content of residual acrylonitrile monomer in styrene/acrylonitrile copolymers and blends by gas chromatography. Bearing

12、 in mind that gas chromatography offers a wide range of possible conditions, the method specified in this International Standard is that shown to have been suitable in practice. 2 Normative reference The following standard contains provisions which, through reference in this text, constitute provisi

13、ons of this International Standard. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the standard ind

14、icated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO2561:1974, Plastics Determination of residual styrene monomer in polystyrene by gas chromatography. 3 Principle A test portion is dissolved in dimethylformamide and a small volume of the solution i

15、njected into a gas chromatograph equipped with flame ionization detector to separate and detect the volatile components. The solvent contains a known amount of propionitrile or acetonitrile as an internal standard for quantitative evaluation. With this method, a lower detection limit of the order of

16、3partspermillion(ppm) of acrylonitrile in the copolymer may be expected. To obtain a lower detection limit of the order of0,3ppm to0,4ppm, an alternative method is specified in Annex A. In this method, the test portion is dissolved in propanediol-(1,2)-carbonate, and the solution is injected into a

17、gas chromatograph equipped with a thermionic nitrogen detector. The solution also contains propionitrile as an internal standard. 4 Reagents During the analysis, use only reagents of recognized analytical grade. Special safety precautions shall be observed when handling the following reagents, espec

18、ially acrylonitrile. 4.1 Dimethylformamide, of purity such that no impurity peaks occur within the range of retention times of the substances to be determined. 4.2 Propionitrile Acetonitrile may be used as internal standard instead of propionitrile, if it has been shown that the same results are obt

19、ained. 4.3 Acrylonitrile 5 Apparatus Ordinary laboratory apparatus, plus the following: 5.1 Gas chromatograph, with flame ionization detector and recorder. Gas-chromatographic operating conditions Column: Stainless-steel or glass tubing,1m to2m length,3mm to4mm internal diameter is recommended. The

20、columm shall be packed with Porapak Q 1)of particle size from50mesh to100mesh. To prevent non-volatile material contained in the test solution from entering the column, suitable means shall be provided, such as a glass liner in the injection port or a pre-column of5cm length with the same packing as

21、 the column and mounted in such a way as to allow frequent renewal. The method of packing is not specified, but shall be such as to obtain a satisfactory separation efficiency of the column. The column shall be aged for24h at230 C with gas flow. Change in column dimensions is permissible only if thi

22、s has proved to give the same results. Column and, if applicable, pre-column temperature:160 C to180 C isothermal. Temperature of injection port:200 C to230 C. Temperature of detector compartment:230 C. Carrier gas: helium (or nitrogen) as specified in ISO2561. Flowrate of carrier gas: to be adjuste

23、d such that propionitrile is eluted in5min to10min. Flame ionization detector in which the hydrogen and air flowrates are adjusted such as to give a) high sensitivity of response; b) a linear relationship between response and concentration in the measured range; c) an only insignificant effect of sm

24、all changes in flowrates on response and sensitivity. Recommended recorder speed:1,0cm/min or 1,27cm/min. 1) Porapak Q is the trade-name of a product of Millipore Corporation. This information is given for the convenience of the users of this International Standard and does not constitute an endorse

25、ment of this product by ISO. By agreement between the interested parties, alternative products of equal performance may be used.BS2782-4:Method 453C:1996 2 BSI 08-1999 The silicone-rubber septum for injection shall have a layer of polytetrafluoroethylene on each side in order to delay attack by dime

26、thylformamide. If the septa available have a protective layer on one side only, two shall be used. Even so, it will be necessary to renew them frequently. 5.2 Microsyringes, of capacity of14l to504l. 5.3 Analytical balance, accurate to within0,5mg. 6 Preparation of test sample The sample may be take

27、n from material in the form of powder, pellets or a moulding. Large pieces shall be reduced to fragments sufficiently small to permit a sample amount as close as possible to1,0g to be weighed out. This size-reduction operation shall not cause the sample to become heated. 7 Procedure 7.1 Preparation

28、of the internal-standard solution Transfer exactly1ml of propionitrile(4.2) by means of a pipette into a100ml one-mark volumetric flask and dilute to the mark with dimethylformamide(4.1), both reagents having been kept at20 C 1,0 C. Transfer with a pipette exactly5ml of the solution thus obtained in

29、to another100ml one-mark volumetric flask and dilute to the mark with dimethylformamide. If necessary, further dilute this diluted solution with dimethylformamide, depending on the acrylonitrile concentration in the polymer sample, in order to be able to use the same detector sensitivity. During the

30、 dilution process, maintain the liquids at a temperature of20 C 1,0 C. 7.2 Preparation of the sample solution Weigh, to the nearest1mg, approximately1g of the polymer sample and transfer to a20ml one-mark volumetric flask fitted with a ground-glass stopper. Add approximately15ml of dimethylformamide

31、(4.1). After closing the flask, allow the polymer to dissolve, with shaking if necessary. After complete dissolution, add exactly1ml of the internal-standard solution, prepared in accordance with7.1 and kept at20 C 1,0 C, from a pipette and dilute to the mark with dimethylformamide. Keep the solutio

32、n for injection into the gas chromatograph. 7.3 Preparation of acrylonitrile solutions for calibration 7.3.1 Preparation of a stock standard solution Weigh, to the nearest1mg,0,1ml of acrylonitrile(4.3) together with an appropriate amount of dimethylformamide(4.1) into a100ml one-mark volumetric fla

33、sk and dilute to the mark with dimethylformamide which has been kept at20 C 0,1 C. Transfer with a pipette exactly10ml of the solution thus obtained into another100ml one-mark volumetric flask and dilute to the mark with dimethylformamide. If necessary, transfer with a pipette exactly20ml of this di

34、luted solution into another100ml one-mark volumetric flask and dilute to the mark with dimethylformamide, for the same reason as mentioned in7.1. Maintain the temperature of the liquid at20 C 0,1 C during the dilution process. Weigh the acrylonitrile, which is very volatile, into the already weighed

35、 amount of dimethylformamide in order to reduce its vapour pressure. 7.3.2 Preparation of calibration solutions Transfer an appropriate volume of the acrylonitrile solution prepared in accordance with7.3.1 and kept at20 C 1,0 C into a20ml one-mark volumetric flask, add exactly1ml of the internal-sta

36、ndard solution(7.1) and dilute to the mark with dimethylformamide(4.1). As appropriate volumes of acrylonitrile solution(7.3.1), the following volumes are recommended: 0,5ml1,0ml1,5ml and2,0ml Keep the solutions for injection into the gas chromatograph. 7.4 Gas-chromatographic recording of sample an

37、d calibration solutions Depending on the sensitivity of the gas chromatograph used, inject a suitable volume of the sample solution prepared in accordance with7.2 or of the calibration solution prepared in accordance with7.3. The volume injected is not critical for the calculation of results, but sh

38、all be identical for corresponding sample and calibration solutions. Record the calibration gas chromatograms always with the same sensitivities for component and internal-standard peaks as those used for the respective sample gas chromatograms. Develop the gas chromatogram until acrylonitrile and t

39、he internal standard have been eluted completely, but not after the initial slope of the dimethylformamide peak appears. Then flush the column (no back-flushing operation is required with this method) until the normal baseline is restored.BS2782-4:Method 453C:1996 BSI 08-1999 3 7.5 Evaluation of gas

40、-chromatographic peaks The retention times of acrylonitrile and propionitrile must be known, at least relative to each other. The values are dependent on column length, column temperature and other parameters, and they vary according to the density of the column packing and the age of the column. Th

41、e peak areas of acrylonitrile and propionitrile are determined by a) electronic integration, b) area estimation on the basis of the equation area (A)=peak height width at half-height (see ISO2561) or c) planimetry. Use of methodb) is recommended only for peaks with a horizontal baseline and having a

42、 shape as close as possible to that of an isosceles triangle, in order to minimize the inaccuracy of measurement. This method has been found appropriate for the analytical procedure described herein. For routine determinations, peak-height measurements of both sample and calibration chromatograms wi

43、ll be sufficient. The method of peak evaluation chosen shall be identical for corresponding peaks of sample and calibration solutions. 8 Expression of results 8.1 Calculation of results from a calibration graph If several calibration solutions with different concentrations of acrylonitrile are avail

44、able, draw a calibration graph by plotting the ratios of peak areas A a /A sagainst the respective concentrations in milligrams per millilitre. With the corresponding ratios determined from the sample solution A a /A s , read the concentration of acrylonitrile in the sample solution c afrom the cali

45、bration graph. Calculate P a , the content of acrylonitrile in the polymer sample, expressed in parts per million (ppm) by mass, from c ausing the equation For routine determinations, peak heights may be used instead of peak areas A a , A s , A aand A s , if this has been verified to lead to the sam

46、e results. 8.2 Calculation of results from a single-point calibration Provided that a linear relationship exists between peak areas and respective concentrations of acrylonitrile, P amay be calculated as follows: 8.3 Precision of measurement and sensitivity The spread of results obtained from replic

47、ate measurements of acrylonitrile concentration in a calibration sample shall not exceed 20% of the mean result or5 ppm absolute, whichever is the greater. A lower limit of detection of the order of3ppm may be expected from the method. 9 Test report The test report shall include the following partic

48、ulars: a) a reference to this International Standard; b) all details necessary for complete identification of the polymer tested; c) any deviation of the gas chromatographic equipment and procedure from the standard equipment with flame ionization detector and procedure specified in the main part of

49、 this International Standard, especially of the method described in Annex A of this International Standard has been applied; d) the content of acrylonitrile monomer, expressed as parts per million (ppm) by mass of the polymer sample and rounded off to the nearest whole number; e) the limit or error as determined from the spread of results (see8.3). . . . (1) where A a is the peak area for acrylonitrile in the calibration solution; A s is the peak area for the internal standard (propionitrile) in the calibration solution; A a is the