1、Designation: D4735 09 (Reapproved 2014)Standard 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 o
2、f 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. Scope1.1 This test method covers the determination of thiophenein refined benzene in the range from 0.8
3、0 to 1.80 mg/kg for 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 inASTM Research Report RR:D16-10
4、38.2The range of the test method may be extended by modifyingthe sample injection volume, split ratios, calibration range, orsample 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
5、may be applicable 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 co
6、nformance to appli-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
7、 units are to be 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 lim
8、itations prior 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Specification for Reagent WaterD1685 Test Method for Traces of Thiophene in Benzene bySpectrophotometry (Withdrawn 2009)4D2359 Specification for Refined Benzene-535D3437 Practice for
9、Sampling and Handling Liquid CyclicProductsD4057 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 Benzen
10、e-545D6809 Guide for Quality Control 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 Practic
11、e for Packed Column Gas ChromatographyE355 Practice for Gas Chromatography Terms and Relation-shipsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE840 Practice for Using Flame Photometric Detectors in GasChromatographyE1510 Practice for Installing Fus
12、ed Silica Open TubularCapillary Columns 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 Feb. 1, 2014. Publishe
13、d February 2014. Originallyapproved in 1987. Last previous edition approved in 2009 as D4735 09. DOI:10.1520/D4735-09R14.2Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D16-1038. ContactASTM CustomerService at serviceastm.org.3F
14、or referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4The last approved version of this historical standard is refer
15、enced onwww.astm.org.*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 States12.2 Other Document:OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.120053. Summary of Test Met
16、hod3.1 The thiophene concentration in refined benzene is de-termined at the milligram thiophene per kilogram sample levelusing conventional gas-liquid chromatography with a flamephotometric detector (FPD) or pulsed flame photometric de-tector (PFPD). A reproducible volume of sample is injected.Quant
17、itative 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 setting specifications onbenzene and for use as an internal quality control tool wherebenzene is either produced or used in a manufactu
18、ring process.4.2 This test method was found applicable for determiningthiophene in refined benzene conforming to the specificationsdescribed in Specification D2359 and may be applicabletoward other grades of benzene if the user has taken thenecessary precautions as described in the text.4.3 This tes
19、t method was developed as an alternative tech-nique to Test Method D1685.5. Apparatus5.1 Gas ChromatographAny chromatograph having aflame photometric detector (FPD or PFPD) may be used whichcan operate at the typical conditions described in Table 1. Theuser is referred to Practices E260 and E355 for
20、 additionalinformation about gas chromatography principles and proce-dures. An automatic sampler is recommended. The GC shouldhave the following performance characteristics:5.1.1 Column Temperature ProgrammerThe chromato-graph shall be capable of linear programmed temperatureoperation over a range s
21、ufficient for the separation of thecompounds of interest. The programming shall be sufficientlyreproducible to obtain retention time repeatability throughoutthe scope of the analysis.5.1.2 Sample Inlet SystemThe sample inlet system shallhave variable temperature control capable of operating con-tinu
22、ously 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 asyringe. For the PFPD a heated flash vaporizing injectordesigned to provide a linear sample split injection (that is,50:1) is required for
23、 proper sample introduction. The associ-ated carrier gas flow controls shall be of sufficient precision toprovide reproducible column flows and split ratios in order tomaintain analytical integrity.5.2 ColumnThe column shall provide complete resolutionof thiophene from benzene and any other hydrocar
24、bon impu-rities because of potential quenching effects by hydrocarbonson the light emissions from the thiophene. The columnsdescribed in Table 1 have been judged satisfactory. The user isreferred to Practice E1510 for assistance on installing fusedsilica capillary columns into the gas chromatograph.
25、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 noise for5Available from U.S. Government Printing Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington,
26、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 Polyethylene Glycol(PEG/CW)Concentration
27、, 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 1.01.5Split Ratio N/A N/A N/A 50:1Column Te
28、mperature, 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 12.0flow optimized for S modeAir 2, mL/min
29、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 09 (2014)2a 4-L injection on the FPD, or a 1.0-L injection for the PFPDof 0.5 mg/kg thiophene in benzene. The user
30、is referred toPractice E840 for assistance in optimizing the operation andperformance of the FPD.5.4 Data Acquisition SystemThe use of an electronicintegrating device or computer data system is recommendedfor determining the detector response. The device and softwareshall have the following capabili
31、ties: a) graphic presentation ofthe chromatogram, b) digital display of chromatographic peakareas, c) identification of peaks by retention time or relativeretention time, or both, d) calculation and use of responsefactors, and e) internal standardization, externalstandardization, and data presentati
32、on.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 ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform t
33、o the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.6Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the dete
34、rmination.6.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water conformingto Type IV of Specification D1193.6.3 Carrier Gas, nitrogen, helium, or hydrogen, chromato-graphic grade, or shall have a purity of 99.999 % (V/V) orbetter.6.4 Hydrogen, zer
35、o 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 shall have a purityof 99.999 % (V/V) or better. (WarningCompressed air andoxygen are gases under high pressure and they supportcom
36、bustion.)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 isatin to 200 mL ofchloroform. Heat under a fume hood to a temperature justbelow the boiling point of chloroform (61C) and maintain for
37、5 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 of benzene ina 1000-mL separatory funnel to which has been added 5 mL ofisatin solution, with successive 100-mL portions of concen
38、-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). Finally,wash with another 100-mL portion of water and filter thebenzene through medium filter paper into a storage bottle,stopper
39、 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 Sulfuric AcidConcentrated H2SO4.6.10 Thiophene.6.11 Stock solutions of thiophene in benzene are commer-cially available and can be use
40、d for preparation of calibrationstandards.7. Hazards7.1 Benzene is considered a hazardous material. Consultcurrent OSHA regulations and suppliers Material Safety DataSheets, and local regulations for all materials used in thismethod.8. Sampling and Handling8.1 Sampling of benzene should follow safe
41、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 benzene.9. Preparation of the Apparatus9.1 The chromatographic separation of trace level sulfurcompounds can be complicated by ab
42、sorption of the sulfurcompounds by the gas chromatographic system. Therefore,care should be taken to properly free the system of active siteswhere absorption or reactions could take place.9.2 Follow the manufacturers instructions for mountingand conditioning the column into the gas chromatograph and
43、adjusting the instrument to conditions described in Table 1.Allow the instrument and detector sufficient time to reachequilibrium.10. Calibration Curve10.1 Prepare a 500-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
44、mL) of thiophene-freebenzene.10.2 Calculate the thiophene content of the stock solutionaccording to the following equation:Thiophene, mg/kg 5 A 3103!/Bwhere:A = weight of thiophene, mgB = weight of benzene, g10.3 Prepare five calibration blends ranging from 0.00 to 5.0mg/kg of thiophene in benzene b
45、y diluting the appropriate6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, 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 th
46、e United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D4735 09 (2014)3volume of stock solution into a known volume of thiophene-free benzene. The user is referred to Practice D4307 forassistance preparation of liquid blends for use as analytical
47、standards.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, 1.75, and 4.35 mg/kg, respectivel
48、y.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.Each standard solution and the blank should be analyzed intriplicate. Injection volumes shall be consistent and reproduc-
49、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 that 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 l
