ASTM_D_4420_-_94_1999e1.pdf

Designation:D 4420 94(Reapproved 1999)e1An American National StandardStandard Test Method forDetermination of Aromatics in Finished Gasoline by GasChromatography1This standard is issued under the fixed designation D 4420;the number immediately following the designation indicates 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.e1NOTEWarning statements were made part of the text in November 1999.1.Scope1.1 This test method provides for the determination ofbenzene,toluene,C8,C9and heavier aromatics,and totalaromatics in finished motor gasoline.It is also applicable togasoline blending components.NOTE1For analysis of gasolines for benzene and toluene,solely,TestMethod D 3606 can be used.1.2 This test method is applicable to the following concen-tration ranges,in liquid volume percent,for the individualaromatics listed above:benzene,0.1 to 5;toluene,1 to 20;C8,3 to 25;C9and heavier,5 to 30,and total aromatics,10 to 80.1.3 It has not been determined whether this test method isapplicable to gasoline containing oxygenates;for example,ethers and alcohols.1.4 Results are reported to the nearest 0.1%by liquidvolume.1.5 The values stated in SI units are to be regarded as thestandard.1.6 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 to use.For specificprecautionary statements see Sections 6.1 through 6.8 and 7.1.2.Referenced Documents2.1 ASTM Standards:D 3606 Test Method for Determination of Benzene andToluene in Finished Motor and Aviation Gasoline by GasChromatography2D 4057 Practice for Manual Sampling of Petroleum andPetroleum Products2D 4307 Practice for Preparation of Liquid Blends for Use asAnalytical Standards2E 260 Practice for Packed Column Gas Chromatography33.Summary of Test Method3.1 A two-column chromatographic system connected to adual-filament thermal conductivity detector(or two single-filament detectors)is used.Areproducible volume of sample isinjected into the column containing a polar liquid phase.Thenonaromatics are directed to the reference side of the detector(or single-filament Detector B)and vented to the atmosphere asthey elute.The column is backflushed immediately before theelution of benzene,and the aromatic portion is directed into thesecond column containing a nonpolar liquid phase.The aro-matic components elute in the order of their boiling points andare detected on the analytical side of the detector(or single-filament Detector A).Immediately after the C8aromatics haveeluted,the flow through the nonpolar column is reversed tobackflush the C9and heavier aromatics from the columnthrough the detector.Quantitative results are obtained from themeasured areas of the recorded aromatic peaks by utilizingfactors obtained from the analysis of a blend of knownaromatic content.4.Significance and Use4.1 A knowledge of aromatics in gasolines is helpful inassessing product quality.Such knowledge can also be an aidin evaluating the health hazard to persons handling and usinggasoline.5.Apparatus5.1 ChromatographAny chromatographic instrument thathas a direct vaporizing injector,backflush system,and athermal conductivity detector,and that can be operated at theconditions given in Table 1,can be employed.Two backflushsystems are shown.Fig.1 is a flow diagram employing an eightport rotary valve,and Fig.2 is a flow diagram using an elevenport linear valve.Either flow pattern may be used.5.1.1 Thermal Conductivity DetectorEither one dual-filament or two single-filament detectors can be used.Withdual-filament detectors,both the analytical side and the refer-ence side are used separately to detect eluting components.Proper detection is achieved by manual or automatic switchingof the signal polarity.Newer gas chromatographs equippedwith single-filament detectors usually have the capability toautomatically switch from one signal output to the other so that1This test method is under the jurisdiction of ASTM Committee D-2 onPetroleum Products and Lubricantsand is the direct responsibility of SubcommitteeD02.04.0Lon Gas Chromatography.Current edition approved July 15,1994.Published September 1994.Originallypublished as D 4420 84.Last previous edition D 4420 89.2Annual Book of ASTM Standards,Vol 05.02.3Annual Book of ASTM Standards,Vol 14.02.1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.they also require only a single recorder or single channel ofintegration.5.1.2 SensitivityAn overall sensitivity sufficient to detect0.1 volume%of benzene with a peak height of at least 3-mmwith a 3-L injection.5.2 Recorder,strip chart.A0 to 1-mV range recordingpotentiometer with a response tim