1、Designation: D 5769 04An American National StandardStandard Test Method forDetermination of Benzene, Toluene, and Total Aromatics inFinished Gasolines by Gas Chromatography/MassSpectrometry1This standard is issued under the fixed designation D 5769; the number immediately following the designation i
2、ndicates the year oforiginal adoption or, in the case of revision, the 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. Scope*1.1 This test method covers the determina
3、tion of benzene,toluene, other specified individual aromatic compounds, andtotal aromatics in finished motor gasoline, including gasolinescontaining oxygenated blending components, by gaschromatography/mass spectrometry (GC/MS).1.2 This test method has been tested for the followingconcentration rang
4、es, in liquid volume percent, for the follow-ing aromatics: benzene, 0.1 to 4 %; toluene, 1 to 13 %; andtotal (C6 to C12) aromatics, 10 to 42 %. The round-robin studydid not test the method for individual hydrocarbon processstreams in a refinery, such as reformates, fluid catalytic crackednaphthas,
5、and so forth, used in the blending of gasolines.1.3 Results are reported to the nearest 0.01 % for benzeneand 0.1 % for the other aromatics by liquid volume.1.4 SI units of measurement are preferred and used through-out this standard.1.5 This standard does not purport to address all of thesafety con
6、cerns, 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 its use.2. Referenced Documents2.1 ASTM Standards:2D 1298 Practice for Density, Relat
7、ive Density (SpecificGravity), or API Gravity of Crude Petroleum and LightPetroleum Products by Hydrometer MethodD 4052 Test Method for Density and Relative Density ofLiquids by Digital Density MeterD 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 4307 Practice for Preparation
8、 of Liquid Blends for Use asAnalytical Standards3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 aromaticany hydrocarbon compound containing abenzene or naphthalene ring.3.1.2 calibrated aromatic componentthe individual aro-matic components that have a specific calibration.3.1.
9、3 cool on-column injectorin gas chromatography,adirect sample introduction system that is set at a temperature ator below the boiling point of solutes or solvent on injection andthen heated at a rate equal to or greater than the column.Normally used to eliminate boiling point discrimination oninject
10、ion or to reduce adsorption on glass liners within injec-tors, or both. The sample is injected directly into the head ofthe capillary column tubing.3.1.4 open split interfaceGC/MS interface used to main-tain atmospheric pressure at capillary column outlet and toeliminate mass spectrometer vacuum eff
11、ects on the capillarycolumn. Can be used to dilute the sample entering the massspectrometer to maintain response linearity.3.1.5 reconstructed ion chromatogram (RIC)a limitedmass chromatogram representing the intensities of ion massspectrometric currents for only those ions having particularmass to
12、charge ratios. Used in this test method to selectivelyextract or identify aromatic components in the presence of acomplex hydrocarbon matrix, such as gasoline.3.1.6 retention gapin gas chromatography, refers to adeactivated precolumn which acts as a zone of low retentionpower for reconcentrating ban
13、ds in space. The polarity of theprecolumn must be similar to that of the analytical column.3.1.7 split ratioin capillary gas chromatography, the ratioof the total flow of carrier gas to the sample inlet versus theflow of the carrier gas to the capillary column, expressed bysplit ratio 5 S1C!/C (1)wh
14、ere:S = flow rate at the splitter vent, andC = flow rate at the column outlet.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.04 on Hydrocarbon Analysis.Current edition approved May 1, 2004. Pub
15、lished June 2004. Originallyapproved in 1995. Last previous edition approved in 1998 as D 576998.2For 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 Docum
16、ent 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 Conshohocken, PA 19428-2959, United States.3.1.8 total ion chromatogram (TIC)mass spectrometercomputer output representing eit
17、her the summed intensities ofall scanned ion currents or a sample of the current in the ionbeam for each spectrum scan plotted against the correspondingspectrum number. Generally, it can be correlated with a flameionization detector chromatogram.3.1.9 uncalibrated aromatic componentindividual aro-ma
18、tics for which a calibration is not available. These compo-nents are estimated from the calibration of several calibratedaromatic components.3.1.10 wall coated open tubular (WCOT)a type of capil-lary column prepared by coating or bonding the inside wall ofthe capillary with a thin film of stationary
19、 phase.4. Summary of Test Method4.1 A gas chromatograph equipped with a dimethylpolysi-loxane WCOT column is interfaced to a fast scanning massspectrometer that is suitable for capillary column GC/MSanalyses. The sample is injected either through a capillarysplitter port or a cool-on-column injector
20、 capable of introduc-ing a small sample size without overloading the column. Thecapillary column is interfaced directly to the mass spectrometeror by way of an open split interface or other appropriate device.4.2 Calibration is performed on a mass basis, using mixturesof specified pure aromatic hydr
21、ocarbons. Volume percent datais calculated from the densities of the individual componentsand the density of the sample. A multipoint calibration consist-ing of at least five levels and bracketing the expected concen-trations of the specified individual aromatics is required.Specified deuterated hyd
22、rocarbons are used as the internalstandards, for example, d6-benzene for quantitating benzene.Unidentified aromatic hydrocarbons present that have not beenspecifically calibrated for are quantitated using the calibrationof an adjacent calibrated compound and summed with the otheraromatic components
23、to obtain a total aromatic concentrationof the sample.4.3 Specified quality control mixture(s), such as syntheticquality control mixtures must be analyzed to monitor theperformance of the calibrated GC/MS system. Analysis of agasoline as a reference material is strongly recommended.5. Significance a
24、nd Use5.1 Test methods to determine benzene and the aromaticcontent of gasoline are necessary to assess product quality andto meet fuel regulations.5.2 This test method can be used for gasolines that containoxygenates (alcohols and ethers) as additives. It has beendetermined that the common oxygenat
25、es found in finishedgasoline do not interfere with the analysis of benzene and otheraromatics by this test method.6. Apparatus6.1 Gas Chromatography:6.1.1 System equipped with temperature-programmable gaschromatograph suitable for split injections with WCOT columnor cool-on-column injector that allo
26、ws the injection of small(for example, 0.1 L) samples at the head of the WCOTcolumn or a retention gap. An autosampler is mandatory for theon-column injections.6.1.2 WCOT column containing dimethylpolysiloxanebonded stationary phase, meeting the specification in thefollowing table. For on-column inj
27、ections, a column containinga thicker film of stationary phase, such as 45 m, is recom-mended to prevent column sample overload.Resolution R between 1,3,5-trimethylbenzene and 1-methyl-2-ethylbenzene at the 3 mass % leveleach must be equal to or greater than2.0R 52t2t1!1.699y2 1 y1!t2 = retention ti
28、me of 1,3,5-trimethylbenzenet1 = retention time of 1-methyl-2-ethylbenzeney2 = peak width at half height of 1,3,5-trimethylbenzeney1 = peak width at half height 1-methyl-2-ethyl benzene6.2 Mass Spectrometry:6.2.1 Mass spectrometer capable of producing electronimpact spectra at 70, or higher, electro
29、n volts or equivalent, andcapable of scanning the range of the specified quantitationmasses or m/e. The mass scan range shall cover the masses ofinterest for quantitation and should yield at least 5 scans acrossthe peak width at half peak width fora1to3mass percenttoluene and cover the masses of int
30、erest for quantitation. Ascan range of 41 to 200 daltons is adequate.6.2.2 The mass spectrometer must be capable of beinginterfaced to a gas chromatograph and WCOT columns. Theinterface must be at a high enough temperature to preventcondensation of components boiling up to 220C, usually 20Cabove the
31、 final column temperature is adequate. Direct columninterface to the mass spectrometer can be used. An open splitinterface with computer controlled programmable flow control-ler(s) can also be used, particularly with cool on-columninjections, to maintain all aromatic components within thelinearity o
32、f the mass spectrometer and at the same timemaintain detectability of lower concentration aromatic compo-nents. For example, a higher open-split-interface make-up gasflow can be used for the high concentration components, suchas toluene and xylenes, and a lower make-up gas flow rate maybe used durin
33、g the elution of the lower concentration benzeneand C9+ components. Other interfaces may be used providedthe criteria specified in Sections 9 and 10 are met.6.2.3 A computer system shall be interfaced to the massspectrometer to allow acquisition of continuous mass scans ortotal ion chromatogram (TIC
34、) for the duration of the chromato-graphic program and be able to analyze repeatedly 0.01 masspercent 1,4-diethylbenzene with the specified signal/noise ratioof 5. Software must be available to allow searching anyGC/MS run for specific ions or reconstructed ions and plottingthe intensity of the ions
35、 with respect to time or scan number.The ability to integrate the area under a specific ion plot peakis essential for quantitation. The quantitation software mustallow linear least squares or quadratic nonlinear regression andquantitation with multiple internal standards. It is also recom-mended tha
36、t software be available to automatically perform theidentification of aromatic components as specified in 13.1.1.7. Reagents and Materials7.1 Carrier GasHelium and hydrogen have been usedsuccessfully. The recommended minimum purity of the carriergas used is 99.999 mol percent. Additional purificatio
37、n usingD5769042commercially available scrubbing reagents may be necessaryto remove trace oxygen, which may deteriorate the perfor-mance of the GC WCOT. (WarningHelium and hydrogenare supplied under high pressure. Hydrogen can be explosiveand requires special handling. Hydrogen monitors that auto-mat
38、ically shut off supply to the GC in case of serious leaks areavailable from GC supply manufacturers.)7.2 Dilution SolventsReagent grade 2,2,4-trimethylpentane (iso-octane), n-heptane, n-nonane, cyclohex-ane, or toluene, or a combination thereof, used as a solvent inthe preparation of the calibration
39、 mixtures. (WarningThegasoline samples and solvents used as reagents such asiso-octane, cyclohexane, n-heptane, n-octane, and toluene, areflammable and may be harmful or fatal if ingested or inhaled.Benzene is a known carcinogen. Use with proper ventilation.Safety glasses and gloves are required whi
40、le preparing samplesand standards. Samples should be kept in well ventilatedlaboratory areas.)NOTE 1Toluene should be used as a solvent only for the preparationof C9+ components and shall be free from interfering aromatics.7.3 Internal StandardsDeuterated analogs of benzene,ethylbenzene, and naphtha
41、lene, as specified in Table 1, shall beused as internal standards because of their similar chromato-graphic characteristics as the components analyzed. The use ofa fourth internal standard toluene-d8 is recommended. Deuter-ated naphthalene is hygroscopic and should be stored awayfrom high humidity.7
42、.4 Standards for Calibration and IdentificationAromatichydrocarbons used to prepare standards should be 99 % orgreater purity (see Table 1). If reagents of high purity are notavailable, an accurate assay of the reagent shall be performedusing a properly calibrated GC or other techniques. Theconcentr
43、ation of the impurities that overlap the other calibra-tion components shall be known and used to correct theconcentration of the calibration components. The use of onlyhigh purity reagents is strongly recommended because of theerror that may be introduced from impurity corrections. Stan-dards are u
44、sed for calibration as well as for establishing theidentification by retention time in conjunction with massspectral match (see 13.1.1). Naphthalene is hygroscopic andshould be stored away from high humidity.8. Sampling8.1 Every effort should be made to ensure that the sample isrepresentative of the
45、 fuel source from which it is taken. Followthe recommendations of Practice D 4057, or its equivalent,when obtaining samples from bulk storage or pipelines. Sam-pling to meet certain regulatory specifications may require theuse of specific sampling procedures. Consult appropriate regu-lations.8.2 App
46、ropriate steps should be taken to minimize the lossof light hydrocarbons from the gasoline sample while samplingand during analyses. Upon receipt in the laboratory, chill thesample in its original container to between 0 to 5C (32 to40F) before and after a sample aliquot is removed for analysis.8.3 A
47、fter the sample is prepared for analysis with internalstandard(s), chill the sample and fill the autosampler vial toapproximately 90 % of its volume. The remainder of thesample should be re-chilled immediately and protected fromevaporation for further analyses, if necessary. To preventevaporation of
48、 the sample, the autosampler vials should bestored at 0 to 5C (32 to 40F) until ready for loading on theautosampler.9. Calibration9.1 Preparation of Calibration StandardsMulti-component calibration standards using all the compounds listedin Table 1 are prepared by mass according to Practice D 4307.T
49、he standards may be prepared by combining the specifiedindividual aromatics either into a single mixture or intoTABLE 1 Mass Spectrometer Quantitation Ions for Sample Components and Internal StandardsCompound CASNo.Primary Ion(Dalton)Internal Standard(ISTD)ISTD ION(Dalton)Benzene 71-43-2 78 Benzene-d6 84 + 83Toluene 108-88-3 92 Ethylbenzene-d10 ortoluene-d8116 + 115 or 100 + 99Ethylbenzene 100-41-4 106 Ethylbenzene-d10 116 + 1151,3-Dimethylbenzene 108-38-3 106 Ethylbenzene-d10 116 + 1151,4-Dimethylbenzene 106-42-3 106 Ethylbenzene-d10 116 + 1151,2-Dimethy
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