1、Designation: D4735 09Standard Test Method forDetermination of Trace Thiophene in Refined Benzene byGas Chromatography1This standard is issued under the fixed designation D4735; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar 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*1.1 This test method covers the determination of thiophenein refined benzene in the range from 0.80 to 1.80 mg/kg f
3、or theFlame Photometric Detector (FPD), and from 0.14 to 2.61mg/kg for the Pulsed Flame Photometric Detector (PFPD). Forthe PFPD, the minimum level of quantitation (LOQ) is 0.14mg/kg and the minimum level of detection (LOD) is 0.04mg/kg, as described in ASTM Research Report RR: D16-1038.2The range o
4、f the test method may be extended bymodifying the sample injection volume, split ratios, calibrationrange, or sample dilution with thiophene-free solvent.1.2 This test method has been found applicable to benzenecharacteristic of the type described in Specifications D2359and D4734 and may be applicab
5、le to other types or grades ofbenzene only after the user has demonstrated that the procedurecan completely resolve thiophene from the other organiccontaminants contained in the sample.1.3 The following applies to all specified limits in this testmethod: for purposes of determining conformance to ap
6、pli-cable specification using this test method, an observed value ora calculated value shall be rounded off “to the nearest unit” inthe last right-hand digit used in expressing the specificationlimit in accordance with the rounding-off method of PracticeE29.1.4 The values stated in SI units are to b
7、e regarded asstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior
8、to use. For specific hazardstatements, see Section 7.2. Referenced Documents2.1 ASTM Standards:3D1193 Specification for Reagent WaterD1685 Test Method for Traces of Thiophene in Benzene bySpectrophotometryD2359 Specification for Refined Benzene-535D3437 Practice for Sampling and Handling Liquid Cycl
9、icProductsD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD4734 Specification for Refined Benzene-545D6809 Guide for Quality Cont
10、rol and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE260 Practice for Packed Column Gas Chromatog
11、raphyE355 Practice for Gas Chromatography Terms and Rela-tionshipsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE840 Practice for Using Flame Photometric Detectors inGas ChromatographyE1510 Practice for Installing Fused Silica Open TubularCapillary C
12、olumns in Gas Chromatographs1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.04 on Instrumental Analysis.Current edition approved Dec. 1, 2009. Published December 2009. Originallyapprov
13、ed in 1987. Last previous edition approved in 2002 as D4735 02. DOI:10.1520/D4735-09.2Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D16-1038.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM
14、Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoho
15、cken, PA 19428-2959, United States.2.2 Other Document:OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.120043. Summary of Test Method3.1 The thiophene concentration in refined benzene is de-termined at the milligram thiophene per kilogram sample levelusing conventional gas-liquid chromatography
16、 with a flamephotometric detector (FPD) or pulsed flame photometric de-tector (PFPD). A reproducible volume of sample is injected.Quantitative results are obtained by the external standardtechnique using the measured peak area of thiophene.4. Significance and Use4.1 This test method is suitable for
17、setting specifications onbenzene and for use as an internal quality control tool wherebenzene is either produced or used in a manufacturing process.4.2 This test method was found applicable for determiningthiophene in refined benzene conforming to the specificationsdescribed in Specification D2359 a
18、nd may be applicabletoward other grades of benzene if the user has taken thenecessary precautions as described in the text.4.3 This test method was developed as an alternative tech-nique to Test Method D1685.5. Apparatus5.1 Gas ChromatographAny chromatograph having aflame photometric detector (FPD o
19、r PFPD) may be used whichcan operate at the typical conditions described in Table 1. Theuser is referred to Practices E260 and E355 for additionalinformation about gas chromatography principles and proce-dures. An automatic sampler is recommended. The GC shouldhave the following performance characte
20、ristics:5.1.1 Column Temperature ProgrammerThe chromato-graph shall be capable of linear programmed temperatureoperation over a range sufficient for the separation of thecompounds of interest. The programming shall be sufficientlyreproducible to obtain retention time repeatability throughoutthe scop
21、e of the analysis.5.1.2 Sample Inlet SystemThe sample inlet system shallhave variable temperature control capable of operating con-tinuously at a temperature up to the maximum column tem-perature employed. The sample inlet system shall allow aconstant volume of sample to be injected by means of asyr
22、inge. For the PFPD a heated flash vaporizing injectordesigned to provide a linear sample split injection (that is,50:1) is required for proper sample introduction. The associ-ated carrier gas flow controls shall be of sufficient precision toprovide reproducible column flows and split ratios in order
23、 tomaintain analytical integrity.5.2 ColumnThe column shall provide complete resolutionof thiophene from benzene and any other hydrocarbon impu-rities because of potential quenching effects by hydrocarbonson the light emissions from the thiophene. The columnsdescribed in Table 1 have been judged sat
24、isfactory. The user isreferred to Practice E1510 for assistance on installing fusedsilica capillary columns into the gas chromatograph.5.3 DetectorAny flame photometric detector (FPD orPFPD) can be used, provided it has sufficient sensitivity toproduce a minimum peak height twice that of the base no
25、ise fora 4-L injection on the FPD, or a 1.0-L injection for the PFPDof 0.5 mg/kg thiophene in benzene. The user is referred toPractice E840 for assistance in optimizing the operation andperformance of the FPD.4Available from U.S. Government Printing Office Superintendent of Documents,732 N. Capitol
26、St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.TABLE 1 Thiophene in Benzene Instrumental ConditionsColumn A B C DTubing 6 ft 318 in.Ni 15ftby18 in. stainless steel 10 ft by18 in. stainless steel 30 meter, Fused Silica,0.25 (or 0.32) mm IDPhase TCEEPASP-1000 OV-351 Bonded Pol
27、yethylene Glycol(PEG/CW)Concentration, weight % 7 10 10 0.5 (or 1.0) micron film thicknessSupport Chromosorb P-AWBSupelcoport Chromosorb P-AW N/AMesh 100/120 60/80 80/100 N/AGas chromatographic conditionsInlet 150 170 180 200Carrier Gas helium helium helium heliumCarrier Flow, mL/min 30 30 30 1.01.5
28、Split Ratio N/A N/A N/A 50:1Column Temperature, C 70 90 70 50C for 1 mi., 10C/min to200C, hold for 1 minDetector FPD FPD FPD PFPD(optimize flows permanufacturers instructions)(tuned for Sulfur)BG-12 Filter2 mm combustorH2, mL/min 140 140 140 11.5flow optimized for S modeAir I, mL/min 80 80 80 12.0fl
29、ow optimized for S modeAir 2, mL/min 70 70 70 10.0flow optimized for S modeTemperature (C) 220 220 250 250ATetracyanoethylated pentaerythritol or pentrile.BChromosorb P is a registered trademark of the Manville Corp.D4735 0925.4 Data Acquisition SystemThe use of an electronicintegrating device or co
30、mputer data system is recommendedfor determining the detector response. The device and softwareshall have the following capabilities: a) graphic presentation ofthe chromatogram, b) digital display of chromatographic peakareas, c) identification of peaks by retention time or relativeretention time, o
31、r both, d) calculation and use of responsefactors, and e) internal standardization, external standardiza-tion, and data presentation.5.5 Microsyringe, 5 or 10-L capacity.5.6 Volumetric Flasks, 50, 100 and 500-mL capacity.5.7 Separatory Funnel, 1-L capacity.6. Reagents and Materials6.1 Purity of Reag
32、entsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.5Other grades may beused, provided
33、it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.6.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water conformingto Type IV of Specification D1193.6.3 Carri
34、er Gas, nitrogen, helium, or hydrogen, chromato-graphic grade, or shall have a purity of 99.999 % (V/V) orbetter.6.4 Hydrogen, zero grade, or shall have a purity of 99.999 %(V/V) or better. (WarningHydrogen is an extremely flam-mable gas under high pressure.)6.5 Compressed Air, hydrocarbon-free, or
35、shall have apurity of 99.999 % (V/V) or better. (WarningCompressedair and oxygen are gases under high pressure and they supportcombustion.)6.6 Cadmium Chloride Solution (20 g/L)Dissolve 20 g ofanhydrous cadmium chloride CdCl2into 200 mL of water anddilute to 1 L.6.7 Isatin SolutionAdd 0.5 g of isati
36、n to 200 mL ofchloroform. Heat under a fume hood to a temperature justbelow the boiling point of chloroform (61C) and maintain for5 min with stirring. Filter the hot solution through hardenedrapid-filter paper into a 250-mL volumetric flask and dilute tovolume.6.8 Benzene, Thiophene-FreeWash 700 mL
37、of benzene ina 1000-mL separatory funnel to which has been added 5 mL ofisatin solution, with successive 100-mL portions of concen-trated sulfuric acid until the H2SO4layer is light yellow orcolorless. Wash the benzene with 100 mL of water, then twicewith 100 mL of cadmium chloride solution (CdCl2).
38、 Finally,wash with another 100-mL portion of water and filter thebenzene through medium filter paper into a storage bottle,stopper the bottle tightly and save for future use. Commercialsources of thiophene-free benzene are available and can beused as an alternative to this cleanup procedure.6.9 Sulf
39、uric AcidConcentrated H2SO4.6.10 Thiophene.6.11 Stock solutions of thiophene in benzene are commer-cially available and can be used for preparation of calibrationstandards.7. Hazards7.1 Benzene is considered a hazardous material. Consultcurrent OSHA regulations and suppliers Material Safety DataShee
40、ts, and local regulations for all materials used in thismethod.8. Sampling and Handling8.1 Sampling of benzene should follow safe rules in order toadhere to all safety precautions as outlined in the latest OSHAregulations. Refer to Practices D3437, D4057, and D4177 forproper sampling and handling of
41、 benzene.9. Preparation of the Apparatus9.1 The chromatographic separation of trace level sulfurcompounds can be complicated by absorption of the sulfurcompounds by the gas chromatographic system. Therefore,care should be taken to properly free the system of active siteswhere absorption or reactions
42、 could take place.9.2 Follow the manufacturers instructions for mountingand conditioning the column into the gas chromatograph andadjusting the instrument to conditions described in Table 1.Allow the instrument and detector sufficient time to reachequilibrium.10. Calibration Curve10.1 Prepare a 500-
43、mL stock solution of thiophene inbenzene at approximately the 100 mg/kg level by adding 0.04g (38.0 L) of thiophene to 435 g (500 mL) of thiophene-freebenzene.10.2 Calculate the thiophene content of the stock solutionaccording to the following equation:Thiophene, mg/kg 5 A 3 103!/Bwhere:A = weight o
44、f thiophene, mgB = weight of benzene, g10.3 Prepare five calibration blends ranging from 0.00 to 5.0mg/kg of thiophene in benzene by diluting the appropriatevolume of stock solution into a known volume of thiophene-free benzene. The user is referred to Practice D4307 forassistance preparation of liq
45、uid blends for use as analyticalstandards.10.4 For example, an 87.0 mg/kg stock solution was pre-pared by dissolving 0.0378 g thiophene into 435 g of benzene.Aliquots of 0.00, 0.75, 1.0, 2.0, and 5.0 mL of stock solutionwere dissolved in 100 mL of thiophene-free benzene toproduce 0.00, 0.65, 0.87, 1
46、.75, and 4.35 mg/kg, respectively.10.5 Inject an appropriate amount of each solution (4.0-Lfor packed column or 1.0-L for capillary column) into the gaschromatograph. Integrate the area under the thiophene peak.5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, W
47、ashington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D4735
48、093Each standard solution and the blank should be analyzed intriplicate. Injection volumes shall be consistent and reproduc-ible.10.6 Prepare a calibration curve by plotting the integratedpeak area versus milligram per kilogram of thiophene.NOTE 1In the sulfur mode, the FPD will exhibit a response t
49、hat is anonlinear power law function. Please refer to Practice E840 for additionalinformation on the characteristics and usage of the FPD. A data systemthat can produce a quadratic curve fit for the calibration range can beutilized for quantification. The PFPD (and some FPDs) can produce asignal representing the square root of the detector response. This can resultin a linearized output and a linear calibration curve which can also be usedfor quantitation.11. Procedure11.1 Inject an appropriate amount of each sample into thegas chromatograph (4
