1、Designation: D7011 10aD7011 15Standard Test Method forDetermination of Trace Thiophene in Refined Benzene byGas Chromatography and Sulfur Selective Detection1This standard is issued under the fixed designation D7011; the number immediately following the designation indicates the year oforiginal adop
2、tion or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This test method covers the determination of thiophene in refined
3、 benzene using gas chromatography and sulfur selectivedetection. The test method is applicable to the determination of thiophene at levels of 0.02 to 2.18 mg thiophene per kg in benzene(mg/kg) on the AED, 0.03 to 1.87 mg/kg on the PFPD, and 0.03 to 2.11 mg/kg on the SCD. The range of the test method
4、 maybe extended by modifying the sample injection volume, split ratios, calibration range, or sample dilution with thiophene-freesolvent.1.2 In determining the conformance of the test results using this method to applicable specifications, results shall be roundedoff in accordance with the rounding-
5、off method of Practice E29.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of t
6、his standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use. For specific hazard statements, see Section 7.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD1685 Test Method for Traces of Thiop
7、hene in Benzene by Spectrophotometry (Withdrawn 2009)3D2359 Specification for Refined Benzene-535D3437 Practice for Sampling and Handling Liquid Cyclic ProductsD4734 Specification for Refined Benzene-545D4735 Test Method for Determination of Trace Thiophene in Refined Benzene by Gas ChromatographyD5
8、871 Specification for Benzene for Cyclohexane FeedstockD6809 Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related MaterialsE29 Practice for Using Significant Digits in Test Data to Determine Conformance with SpecificationsE177 Practice for Use of the Terms
9、 Precision and Bias in ASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodE1510 Practice for Installing Fused Silica Open Tubular Capillary Columns in Gas Chromatographs2.2 Other Document:OSHA Regulations, 29 CFR paragraphs 1910.1000 and
10、 1910.120033. Summary of Test Method3.1 The thiophene concentration in refined benzene is determined at the sub-mg/kg to low mg/kg level using conventional gaschromatography with a sulfur selective detector. A reproducible volume of sample is injected. Quantitative results are obtained bythe use of
11、the external standard calibration technique.1 This test method is under the jurisdiction of ASTM Committee D16 on Aromatic Hydrocarbons and Related Chemicals and is the direct responsibility of SubcommitteeD16.04 on Instrumental Analysis.Current edition approved Dec. 1, 2010June 1, 2015. Published D
12、ecember 2010July 2015. Originally approved in 2004. Last previous edition approved in 2010 asD7011 10.D7011 10a. DOI: 10.1520/D7011-10A.10.1520/D7011-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM St
13、andardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from U.S. Government Printing Office Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.This document is not an ASTM standard and i
14、s intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the
15、 current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2 The method allows the
16、use of a sulfur chemiluminescence detector, atomic emission detector, pulsed flame photometricdetector, or any other sulfur selective detector provided that its performance meets requirements as set forth in 5.4. As sulfurcompounds elute from the gas chromatographic column, they are detected and qua
17、ntified. While the benzene molecule does notcontain any sulfur atoms, the possibility of matrix quenching and interference is a concern, especially for thiophene determinationat levels less than about 0.5 mg/kg. The column and conditions specified in Table 1 yield acceptable results with minimal mat
18、rixquenching and interference. Employing the column and conditions listed in Table 1 is not a requirement to meet the needs of allusers. For example, there is less concern of quenching and interference encountered with thiophene concentration levels greaterthan 0.5 mg/kg. Users of flame photometric
19、detectors should refer to Test Method D4735.4. Significance and Use4.1 Accurate gas chromatographic determination of trace levels of thiophene in benzene involves special analytical problemsbecause of the difficulties of trace level analysis. These problems arise from the low concentration levels th
20、at need to be measured,the type of column and detector needed for analysis, and the potential interference from the benzene matrix.4.2 This test method was found applicable for determining thiophene in refined benzene conforming to the specificationsdescribed in Specifications D2359, D4734, and D587
21、1 and may be applicable toward other grades of benzene if the user has takenthe necessary precautions as described in the text.4.3 This test method was developed as an alternative technique to Test MethodsMethod D1685 and D4735.5. Apparatus5.1 Gas ChromatographThe gas chromatograph shall be capable
22、of producing retention times for thiophene repeatable towithin 0.05 min. The gas chromatograph shall be equipped with an appropriate sulfur selective detector, column for separation,and sample inlet system for repeatable injection of sample volume.5.2 ColumnSpecifications and conditions described in
23、 Table 1 have been judged satisfactory for this analysis. The use of anycolumn that permits separation and determination of thiophene in benzene at levels consistent with the scope of this method isallowed. Specific chromatographic results and conditions are illustrated in Fig. 1. The user is referr
24、ed to Practice E1510 forinformation on installation of fused silica capillary columns.5.3 Sample Inlet SystemThe sample inlet system shall be able to quantitatively transfer the sample to the analytical column.It shall be capable of introducing constant and repeatable volumes of sample and calibrati
25、on standards. Use of a liquid autosampleror liquid sampling valve is permitted for the analysis of thiophene in benzene.5.4 DetectorA sulfur selective detector is used and shall meet or exceed the following specifications: (1) linearity orcompensated linearity of at least 102, (2) minimum detectable
26、 level of less than 0.02 mg/kg thiophene in benzene, (3) selectivityof sulfur to carbon greater than 105, and (4) absence of quenching that affect results under the conditions used for the analysis.5.5 Data Handling SystemUse of an electronic integrating device or computer is necessary. The device s
27、hall have thefollowing capabilities: (1) graphic presentation of the chromatogram, (2) digital display of chromatographic peak areas, (3)identification of peaks by retention time, and (4) calculation and use of response factors.5.6 Gases:5.6.1 Carrier GasesHelium or nitrogen of high purity (99.995+
28、%). Additional purification is recommended by the use ofmolecular sieves or other suitable agents to remove water, oxygen, hydrocarbons, and sulfur contaminants. Gases shall be regulatedto ensure a constant carrier gas flow rate.5.6.2 Detector GasesHydrogen and air are required as detector gases (99
29、.995+ % purity). Additionally, oxygen (99.8+ %)may be substituted for air. These gases shall be free of interfering contaminants, especially sulfur compounds.5.6.3 Carrier and Detector Gas ControlConstant flow control of carrier and detector gases is critical to optimum andconsistent analytical perf
30、ormance. Control is best provided by the use of pressure regulators and fixed flow restrictions or massflow controllers capable of maintaining gas flow constant to 61 % at the required flow rates. The gas flow rate is measured by anyTABLE 1 Typical Chromatographic ConditionsColumn 30 m length, 0.32
31、mm internaldiameter, 1 m thick film,cross-linked polyethyleneglycol (wax-type)Oven Temperature 40C for 2 min; ramp to 100Cat 10C/min, hold at100C for 1 minFlow Rate 2 mL/minSplit Ratio 1:4 to 1:10Injection Temperature 125CInjection Volume 1-2 LD7011 152NOTE 1The shorter retention time obtained with
32、the SCD is primarily due to the column outlet being at sub-ambient pressure.FIG. 1 Chromatograms Illustrating the Analysis of a Sample Containing 0.2 mg/kg Thiophene in Benzene Using AED, PFPD and SCD(Upper, Middle, and Lower Chromatograms, Respectively)D7011 153appropriate means. The supply pressur
33、e of the gas delivered to the gas chromatograph shall be at least 70 kPa (10 psig) greaterthan the regulated gas at the instrument to compensate for the system back pressure of the flow controllers. In general, a supplypressure of 550 kPa (80 psig) is satisfactory.5.7 Microsyringes10, 50, 100, and 2
34、50 L capacity (61 % accuracy).5.8 Volumetric Pipettes0.5, 1.0, and 2.0 mL capacity (Class A).5.9 Volumetric Flasks10, 50, 100, and 500 mL capacity (class A).5.10 Separatory Funnel1 L capacity.6. Reagents and Materials6.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless ot
35、herwise indicated, it is intended that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society,4 wheresuch specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently hig
36、hpurity to permit its use without lessening the accuracy of the determination.6.2 Purity of WaterUnless otherwise indicated, reference to water shall be understood to mean reagent water conforming toType IV of Specification D1193.6.3 Benzene, Thiophene-free:6.3.1 In a fume hood, wash 700 mLof benzen
37、e in a 1000 mLseparatory funnel to which has been added 5 mLof isatin solution,with successive 100 mL portions of concentrated sulfuric acid until the acid layer is light yellow to colorless. Wash the benzenewith 100 mL of water, then twice with 100 mL of cadmium chloride solution (CdCl2). Finally w
38、ash with another 100 mL portionof water and filter the benzene through medium filter paper into a storage bottle, stopper the bottle tightly and save for future use.6.3.2 Alternatively, thiophene-free benzene can be purchased commercially and used within this method, if its thiophene levelmeets the
39、criteria within 10.4.6.4 Cadmium Chloride Solution (20 g/L)Dissolve 20 g of anhydrous cadmium chloride (CdCl2) into 200 mL of water anddilute to 1 L.6.5 ChloroformReagent grade or better.6.6 Isatin SolutionAdd 0.5 g of isatin to 200 mL of chloroform. Heat under a fume hood to a temperature just belo
40、w theboiling point of chloroform (61C) and maintain for 5 min with stirring. Filter the hot solution through hardened rapid-filter paperinto a 250 mL volumetric flask and dilute to volume with chloroform.6.7 Stock SolutionsCommercially prepared stock solution of thiophene in benzene are available fo
41、r use as calibrationstandards or for preparation of calibration standards.6.8 Sulfuric AcidConcentrated H2SO4.6.9 ThiopheneAvailable from commercial sources for preparation of calibration standards, minimum 99 % purity.7. Hazards7.1 Benzene is listed as a known carcinogen and is considered a hazardo
42、us material. Consult current OSHA regulations andsuppliers Material suppliers Safety Data Sheets for all materials used in this method.7.2 Helium and nitrogen are compressed gases under high pressure and can cause asphyxiation.7.3 Hydrogen is an extremely flammable gas under high pressure.7.4 Compre
43、ssed air and oxygen are gases under high pressure and they support combustion.7.5 Sulfur compounds are generally flammable, toxic, and produce noxious odors, and therefore shall be handled withappropriate precautions for safety.7.6 Isatin is a toxic, cancer causing agent.7.7 Chloroform is flammable,
44、 toxic and is a carcinogen.7.8 Cadmium chloride is a highly toxic cancer causing agent.8. Sample Handling8.1 Collect the samples in accordance with Practice D3437.4 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing
45、of reagents not listed bythe American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.D7011 1548.2 To preserve sample integrity and prev
46、ent the loss of volatile compounds that may be in some samples, collect samples witha minimal head space and do not uncover samples any longer than necessary. Some headspace is necessary to prevent containersfrom rupturing if the possibility for thermal expansion exists. Sample containers shall be f
47、ree of contaminants that could interferewith the analysis. Analyze the specimen as soon as possible after transferring it from the sample container to prevent loss ofcomponents or contamination.8.3 Since this procedure is intended for trace level contamination, care shall be taken to ensure containe
48、rs used for the sample,the specimen, and the working standard do not alter the sample results.9. Preparation of Apparatus9.1 The chromatographic separation of trace level sulfur compounds can be complicated by absorption onto active sitesthroughout the chromatographic system. This is less of a probl
49、em with thiophene, which is very stable relative to most sulfurcompounds. The most likely cause of error in this method is presence of thiophene in matrix blanks (see 10.4).9.2 Follow the manufacturers instructions for mounting the column into the gas chromatograph and adjusting the instrumentto typical conditions as described in Table 1. General guidelines for the installation of capillary columns can be found in PracticeE1510.9.3 The gas chromatograph and detector should be placed into service in accordance with the manufacturers instruct
