1、Designation: D5769 10 (Reapproved 2015)Standard Test Method forDetermination of Benzene, Toluene, and Total Aromatics inFinished Gasolines by Gas Chromatography/MassSpectrometry1This standard is issued under the fixed designation D5769; the number immediately following the designation indicates the
2、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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of benzene
3、,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 ranges, in liquid v
4、olume percent, for the follow-ing aromatics: benzene, 0.1 % to 4 %; toluene, 1 % to 13 %;and total (C6 to C12) aromatics, 10 % to 42 %. The round-robin study did not test the method for individual hydrocarbonprocess streams in a refinery, such as reformates, fluid catalyticcracked naphthas, and so f
5、orth, used in the blending ofgasolines.1.3 Results are reported to the nearest 0.01 % for benzeneand 0.1 % for the other aromatics by liquid volume.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not p
6、urport 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 its use.2. Referenced Documents2.1 ASTM Standar
7、ds:2D1298 Test Method for Density, Relative Density, or APIGravity of Crude Petroleum and Liquid Petroleum Prod-ucts by Hydrometer MethodD4052 Test Method for Density, Relative Density, and APIGravity of Liquids by Digital Density MeterD4057 Practice for Manual Sampling of Petroleum andPetroleum Pro
8、ductsD4307 Practice for Preparation 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 th
9、at have a specific calibration.3.1.3 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 bo
10、iling point discrimination oninjection or to reduce adsorption on glass liners withininjectors, or both. The sample is injected directly into the headof the capillary column tubing.3.1.4 open split interfaceGC/MS interface used to main-tain atmospheric pressure at capillary column outlet and toelimi
11、nate mass spectrometer vacuum effects 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 tho
12、se ions having particularmass to 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 reten
13、tionpower for reconcentrating bands 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, expre
14、ssed by:1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.04.0M on Mass Spectroscopy.Current edition approved June 1, 2015. Published July 2015. Originally approvedin 1995. Last pre
15、vious edition approved in 2010 as D5769 10. DOI: 10.1520/D5769-10R15.2For 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 Document Summary page onthe ASTM
16、website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1split ratio 5 S1C!/C (1)where:S = flow rate at the splitter vent, andC = flow rate at the column outlet.3.1.8 total ion chromatogram (TIC)mass spectrometercomputer output represe
17、nting either 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 componentindividu
18、al aro-matics 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 s
19、tationary 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
20、 injector 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 arom
21、atic hydrocarbons. 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 deute
22、rated hydrocarbons 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 co
23、mponents 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. Signi
24、ficance and 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
25、 oxygenates 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
26、that allows 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-co
27、lumn injections, 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 52st1 2 t2d1.699sy21y1dt2 = r
28、etention time of 1,3,5-trimethylbenzenet1 = retention time of1-methyl-2-ethylbenzeney2 = peak width at half heightof 1,3,5-trimethylbenzeney1 = peak width at half height1-methyl-2-ethyl benzene6.2 Mass Spectrometry:6.2.1 Mass spectrometer capable of producing electronimpact spectra at 70, or higher,
29、 electron 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 masse
30、s of interest 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 220 C, usually20 C
31、 above the final column temperature is adequate. Directcolumn interface to the mass spectrometer can be used. Anopen split interface with computer controlled programmableflow controller(s) can also be used, particularly with coolon-column injections, to maintain all aromatic componentswithin the lin
32、earity of the mass spectrometer and at the sametime maintain detectability of lower concentration aromaticcomponents. For example, a higher open-split-interfacemake-up gas flow can be used for the high concentrationcomponents, such as toluene and xylenes, and a lower make-upgas flow rate may be used
33、 during the elution of the lowerconcentration benzene and C9+ components. Other interfacesmay be used provided the criteria specified in Sections 9 and 10are met.6.2.3 A computer system shall be interfaced to the massspectrometer to allow acquisition of continuous mass scans ortotal ion chromatogram
34、 (TIC) 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
35、 ions 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 andD5769 10 (2015)2quantitation with multiple internal standards. It is
36、also recom-mended that 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. A
37、dditional purification usingcommercially 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
38、that auto-matically 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,cyclohexane, or toluene, or a combination thereof, used as asolvent in the preparation of the
39、calibration mixtures.(WarningThe gasoline samples and solvents used as re-agents such as iso-octane, cyclohexane, n-heptane, n-octane,and toluene, are flammable and may be harmful or fatal ifingested or inhaled. Benzene is a known carcinogen. Use withproper ventilation. Safety glasses and gloves are
40、 required whilepreparing samples and standards. Samples should be kept inwell ventilated laboratory 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
41、, and naphthalene, 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 hi
42、gh humidity.7.4 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
43、. Theconcentration 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. Sta
44、n-dards are used 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 isrepresen
45、tative of the fuel source from which it is taken. Followthe recommendations of Practice D4057, 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-lat
46、ions.8.2 Appropriate 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 before andafter 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 preventTABLE 1 Mass S
48、pectrometer 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
49、 + 1151,3-Dimethylbenzene 108-38-3 106 Ethylbenzene-d10 116 + 1151,4-Dimethylbenzene 106-42-3 106 Ethylbenzene-d10 116 + 1151,2-Dimethylbenzene 95-47-6 106 Ethylbenzene-d10 116 + 115(1-Methylethyl)-benzene 98-82-8 120 Ethylbenzene-d10 116 + 115Propyl-benzene 103-65-1 120 Ethylbenzene-d10 116 + 1151-Methyl-3-ethylbenzene 620-14-4 120 Ethylbenzene-d10 116 + 1151-Methyl-4-ethylbenzene 622-96-8 120 Ethylbenzene-d10 116 + 1151,3,5-Trimethylbenzene 108-67-8 120 Ethylbenzene-d10 116 + 1151-Methyl-2-ethylbenzene 611-14-3 120 Ethylbenzene-d10 116 + 1151,2,4-Trimethylb
