1、 DEUTSCHE NORMFebruary 2005DIN 51438 ICS 71.080.15 Supersedes DIN 51438:1991-09 Testing of benzene and benzene homologues Determination of the thiophene content of benzene Gas chromatography Prfung von Benzol und Benzolhomologen Bestimmung des Gehaltes an Thiophen in Benzol Gaschromatographie Docume
2、nt comprises 5 pagesTranslation by DIN-Sprachendienst. In case of doubt, the German-language original should be consulted as the authoritative text. No part of this translation may be reproduced without prior permission of DIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Ber
3、lin, Germany, has the exclusive right of sale for German Standards (DIN-Normen). English price group 6 www.din.de www.beuth.de !,o-G“11.06 9761036DIN 51438:2005-02 2 Foreword This standard has been prepared by Technical Committee 614 Gaschromatographische Analyse in collaboration with Technical Comm
4、ittee 644 Prfung von Spezialbenzinen, Testbenzinen, Lsemitteln of the Fachausschuss Minerall- und Brennstoffnormung of the Normenausschuss Materialprfung (Materials Testing Standards Committee). Amendments This standard differs from DIN 51438:1991-09 as follows: a) The standard has been editorially
5、revised. b) The normative references have been updated. Previous edition DIN 51438: 1991-09 1 Scope This standard specifies a gas chromatographic (GC) method of determining thiophene contents of between 0,05 mg/kg and 1,5 mg/kg of benzene meeting the requirements of DIN 51633. The test provides info
6、rmation about the degree of purity of the benzene prior to use in subsequent industrial processes. When handling benzene, the relevant safety instructions and national regulations are to be observed (e.g. Verordnung ber brennbare Flssigkeiten (German Regulation on flammable liquids) or Gefahrstoff-v
7、erordnung (German Regulation on dangerous substances and materials). 2 Normative references This standard incorporates, by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text, and the titles of the publications ar
8、e listed below. For dated references, subsequent amendments to or revisions of any of these publications apply to this standard only when incorporated in it by amendment or revision. For undated references, the latest edition of the publication referred to (including any amendments) applies. DIN 514
9、05, Testing of liquid petroleum products, related liquids and solvents for paints and varnishes by gas chromatography General DIN 51633, Benzene and benzene homologues DIN 51750-1, Sampling of petroleum products General DIN 51750-2, Sampling of liquid petroleum products DIN EN ISO 4259, Petroleum pr
10、oducts Determination and application of precision data in relation to methods of test DIN 51438:2005-02 3 Verordnung ber brennbare Flssigkeiten (German Regulation on flammable liquids), as of 13 December 1996, BGBl. (German Federal Law Gazette) I, 1996, 65, pp. 1937-19521)Gefahrstoffverordnung (Germ
11、an Regulation on dangerous substances and materials), as of 15 November 1999, BGBl. (German Federal Law Gazette) I, 1999, No. 52, p. 2233-22811)3 Principle Using a polar separating column, the thiophene is first separated by gas chromatography from the other constituents and then fed by column switc
12、hing via a second separating column to a flame-photometric detector (FPD). External standards are used for the determination. It is important to check for quenching effects, i.e. a negative peak simultaneously produced by hydrocarbon and sulfur components. 4 Designation Designation of the method of
13、determining thiophene in benzene by gas chromatography (GC): Test DIN 51438 GC 5 Apparatus and reagents The following apparatus and reagents shall be used. 5.1 Gas chromatograph, complying with the general requirements of DIN 51405 and equipped with a flame-photometric detector (FPD) and column swit
14、ching, capable of reliably determining thiophene even at a concentration of 0,05 mg/kg. 5.2 Capillary separating column, containing a polar substance as stationary phase. NOTE In interlaboratory tests, 30 m fused silica capillary columns having an internal diameter of 0,53 mm and coated with polyeth
15、ylene glycol (mean molar mass 6 105g/mol) have proved suitable. 5.3 Injection syringes, of capacity 10 l and 100 l. 5.4 Sample vessel, of 50 ml capacity, having a self-sealing rubber membrane closure coated with polytetrafluoroethylene (PTFE). 5.5 Gases, having a purity of not less than 99,995 %. Cf
16、. DIN 51405. Nitrogen, as carrier gas. Hydrogen and air, as detector gases. 1)Registered in the DITR database of DIN Software GmbH, obtainable from Beuth Verlag GmbH, 10772 Berlin, Germany. DIN 51438:2005-02 4 5.6 Benzene, with a thiophene content of less than 20 g/kg. NOTE Benzene containing less t
17、han 20 g/kg of thiophene can be prepared by extracting the thiophene with not less than 98 % (m/m) sulfuric acid, H2SO4, washing the benzene with distilled water until it is neutral and drying it by means of a soft fluted filter. 5.7 Thiophene, with a purity exceeding 99 % (m/m), as external standar
18、d. 5.8 Benzene reference solutions, containing 0,05 mg/kg to 1,5 mg/kg of thiophene. 6 Sampling As specified in DIN 51750-1 and DIN 51750-2. 7 Procedure 7.1 Preparation of apparatus and test conditions Cf. DIN 51405. Adjust the pressure and speed of the carrier gas so that, for a given column temper
19、ature, thiophene can be separated completely from the other components by column switching. 7.2 Sample size and sample application Cf. DIN 51405. Choose the amount of sample injected so that the GC system can reliably separate the thiophene from the other constituents. 7.3 Recording As specified in
20、DIN 51405. 8 Evaluation Cf. DIN 51405. Determine the content of thiophene in the sample, w, in mg/kg, from a calibration graph prepared using the reference solutions. Since the FDP is nonlinear, it is recommended that the graph has more than four measurement points in the vicinity of the expected th
21、iophene content of the sample under test. 9 Expression of results Refer to this standard and report the thiophene content, w, in mg/kg rounded to the nearest 0,1 mg/kg. 10 Precision As specified in DIN EN ISO 4259. DIN 51438:2005-02 5 10.1 Repeatability limit (same operator, same equipment) The abso
22、lute difference between two successive results obtained under repeatability conditions will not exceed the repeatability limit, r, shown in figure 1 in more than 5 % of cases. 10.2 Reproducibility limit (different operators, different equipment) The absolute difference between two individual results obtained under reproducibility conditions will not exceed the reproducibility limit, R, shown in figure 1 in more than 5 % of cases. Figure 1 Repeatability limit, r, and reproducibility limit, R
