1、Designation: D 4735 02Standard Test Method forDetermination of Trace Thiophene in Refined Benzene byGas Chromatography1This standard is issued under the fixed designation D 4735; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 0.5 mg/kg to 5.0 m
3、g/kg.The 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 D 2359and D 4734 a
4、nd 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
5、 conformance 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 PracticeE 29.1.4 This standard does
6、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 to use. For specific hazardstatements, see Se
7、ction 7.2. Referenced Documents2.1 ASTM Standards:D 1193 Specification for Reagent Water2D 1685 Test Method for Traces of Thiophene in Benzene bySpectrophotometry3D 2359 Specification for Refined Benzene-5353D 3437 Practice for Sampling and Handling Liquid CyclicProducts3D 4057 Practice for Manual S
8、ampling of Petroleum andPetroleum Products4D 4177 Practice for Automatic Sampling of Petroleum andPetroleum Products4D 4307 Practice for the Preparation of Liquid Blends forUse as Analytical Standards4D 4734 Specification for Refined Benzene 5453E 29 Practice for Using Significant Digits in Test Dat
9、a toDetermine Conformance with Specifications5E 260 Practice for Packed Column Gas Chromatography5E 355 Practice for Gas Chromatography Terms and Rela-tionships6E 840 Practice for Using Flame Photometric Detectors inGas Chromatography5E 1510 Practice for Installing Fused Silica Open TubularCapillary
10、 Columns in Gas Chromatographs62.2 Other Document:OSHA Regulations, 29 CFR, paragraphs 1910.1000 and1910.120073. 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 wi
11、th 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 set
12、ting 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 D 2359 and
13、 may be applicabletoward other grades of benzene if the user has taken thenecessary precautions as described in the text.1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.04 on Instrumen
14、tal Analysis.Current edition approved July 10, 2002. Published September 2002. Originallypublished as D 4735 87. Last previous edition D 4735 96 (2000).2Annual Book of ASTM Standards, Vol 11.01.3Annual Book of ASTM Standards, Vol 06.04.4Annual Book of ASTM Standards, Vol 05.02.5Annual Book of ASTM S
15、tandards, Vol 14.02.6Annual Book of ASTM Standards, Vol 03.06.7Available from Superintendent of Documents, U.S. Government PrintingOffice, Washington, DC 20402.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.3 This test method was
16、developed as an alternative tech-nique to Test Method D 1685.5. 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 E 260 and E 355 for additiona
17、linformation 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 sufficient
18、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-tinuously at a
19、 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 proper sa
20、mple 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 hydrocarbon impu-r
21、ities 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 E 1510 for assistance on installing fusedsilica capillary columns into the gas chromatograph.5.3 Detec
22、torAny flame photometric detector (FPD orPFPD) can be used, provided it has sufficient sensitivity toproduce a minimum peak height twice that of the base noise 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 E 840 for
23、 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 capabilities: a) graphic presentation o
24、fthe 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, external standardiza-tion, and data presentation.5.5 Microsyringe, 5 or 10-
25、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 to the specifications of the C
26、ommit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.8Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.8Reagent Chemicals,
27、 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 the United States Pharmacopeiaand National Form
28、ulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.TABLE 1 Thiophene in Benzene Instrumental ConditionsColumn A B C DTubing 6 ft 318 in. Ni 15 ft by18 in. stainless steel 10 ft by18 in. stainless steel 30 meter, Fused Silica, 0.25 (or0.32) mm IDPhase TCEEPASP-1000 OV-351 Bonded Polyethy
29、lene 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 1.01.5Split
30、 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 12.0flow op
31、timized 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.D47350226.2 Purity of WaterUnless otherwise indicated, referenceto water shall be underst
32、ood to mean reagent water conformingto Type IV of Specification D 1193.6.3 Carrier Gas, nitrogen, helium, or hydrogen, chromato-graphic grade, or shall have a purity of 99.999 % (V/V) orbetter.6.4 Hydrogen, zero grade, or shall have a purity of 99.999 %(V/V) or better. (WarningHydrogen is an extreme
33、ly flam-mable gas under high pressure.)6.5 Compressed Air, hydrocarbon-free, or 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
34、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 for5 min with stirring. Filter the hot solution through hardenedrapid-filter paper into a 250
35、-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-trated sulfuric acid until the H2SO4layer is light yellow orcolorless. Wash the benzene w
36、ith 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 the bottle tightly and save for future use. Commercialsources of thiophene-free benzene a
37、re 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 used for preparation of calibrationstandards.7. Hazards7.1 Benzene is considered a hazardous
38、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 rules in order toadhere to all safety precautions as outlined in the latest OSHAregulation
39、s. Refer to Practices D 3437, D 4057, and D 4177 forproper sampling and handling of 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 shoul
40、d 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 andadjusting the instrument to conditions described in Table 1.Allow the instrument and de
41、tector 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 mL) of thiophene-freebenzene.10.2 Calculate the thiophene content of the stock solution
42、according to the following equation:Thiophene, mg/kg 5 A 3 103!/Bwhere:A = weight of thiophene, mg, andB = weight of benzene, g.10.3 Prepare five calibration blends ranging from 0.00 to 5.0mg/kg of thiophene in benzene by diluting the appropriateFIG. 1 Chromatogram Illustrating the Analysis of 1.10
43、mg/kg Thiophene in Benzene on an FPDD4735023volume of stock solution into a known volume of thiophene-free benzene. The user is referred to Practice D 4307 forassistance preparation of liquid blends for use as analyticalstandards.10.4 For example, an 87.0 mg/kg stock solution was pre-pared by dissol
44、ving 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, respectively.10.5 Inject an appropriate amount of each solution (4.0-Lfor packed column or
45、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-ible.10.6 Prepare a calibration curve by plotting the integratedpeak area versus
46、 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 E 840 for additionalinformation on the characteristics and usage of the FPD. A data systemthat can produce a quadratic curve fit for the cali
47、bration 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 amo
48、unt of each sample into thegas chromatograph (4.0-L for packed columns and 1.0-L forcapillary columns).11.2 Measure the area of the thiophene peak. The measure-ment of the sample peak should be consistent with the methodfor measuring peak areas in the calibration standards. A typicalchromatogram is
49、shown in Fig. 1 representing 1.10 mg/kgthiophene in benzene on the FPD. A typical chromatogram isshown in Fig. 2 representing 3.0 mg/kg thiophene in benzeneusing the capillary column and PFPD. A typical chromatogramis shown in Fig. 3 representing 0.5 mg/kg thiophene in benzeneusing the capillary column and PFPD.12. Calculation12.1 Determine the amount of thiophene directly from thecalibration curve prepared in 10.6 or from the data processorresults.13. Report13.1 Report the thiophene concentration to the nearest 0.01mg/kg.14. Precision and Bias14
