ASTM_D_7576_-_10.pdf

Designation:D757610Standard Test Method forDetermination of Benzene and Total Aromatics in DenaturedFuel Ethanol by Gas Chromatography1This standard is issued under the fixed designation D7576;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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of benzeneand total aromatics in finished denatured fuel ethanol by gaschromatography.1.2 Total aromatics are determined by adding the concen-trations of benzene,toluene,ethylbenzene,o-xylene,m-xylene,p-xylene,and C9and heavier aromatics.1.3 The aromatic hydrocarbons are separated without inter-ferences from other hydrocarbons in denatured fuel ethanol.Nonaromatic hydrocarbons having boiling point greater thanthat of n-dodecane can cause interferences with the determi-nation of the C9and heavier aromatics.For the C8aromatics,p-xylene and m-xylene co-elute while ethylbenzene ando-xylene are separated.The C9and heavier aromatics aredetermined as a single group.1.4 This test method covers the following concentrationranges:benzene,0.01 to 0.06 vol%and total aromatics,0.25 to2.10 vol%.1.5 Results are reported to the nearest 0.01%by mass orliquid volume.1.6 The values stated in SI units are to be regarded asstandard.The values given in parentheses are provided forinformation only;they may not be exact equivalents.1.7 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.2.Referenced Documents2.1 ASTM Standards:2D1298 Test Method for Density,Relative Density(SpecificGravity),or API Gravity of Crude Petroleum and LiquidPetroleum Products by Hydrometer MethodD4052 Test Method for Density,Relative Density,and APIGravity of Liquids by Digital Density MeterD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD5580 Test Method for Determination of Benzene,Toluene,Ethylbenzene,p/m-Xylene,o-Xylene,C9and HeavierAromatics,and Total Aromatics in Finished Gasoline byGas ChromatographyE355 Practice for Gas Chromatography Terms and Relation-ships3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 1,2,3-tris-2-cyanoethoxypropane(TCEP)polar gaschromatographic liquid phase.3.1.2 aromatic,nany organic compound containing abenzene ring.3.1.3 low-volume connector,nspecial union for connect-ing two lengths of narrow bore tubing 1.6-mm(0.06-in.)outside diameter and smaller;sometimes this is referred to aszero dead volume union.3.1.4 narrow bore tubingtubing used to transfer compo-nents prior to or after separation;usually 0.5-mm(0.02-in.)inside diameter and smaller.3.1.5 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 by:split ratio5S1C!/C(1)where:S=flow rate at the splitter vent,andC=flow rate at the column outlet.3.1.6 wall-coated open tubular(WCOT)type of capillarycolumn prepared by coating the inside wall of the capillarywith a thin film of stationary phase.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.04.0L on Gas Chromatography Methods.Current edition approved March 1,2010.Published April 2010.DOI:10.1520/D757610.2For 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 website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.Summary of Test Method4.1 A two-column chromatographic system equipped with acolumn switching valve and a flame ionization detector is used.A reproducible volume of sample containing an appropriateinternal standard,such as 2-hexanone,is injected onto aprecolumn containing a polar liquid phase(TCEP).The C9andlighter nonaromatics are vented to the atmosphere as they elutefrom the precolumn.A thermal conductivity detector may beused to monitor this separation.The TCEP precolumn isbackflushed immediately before the elution of benzene,and theremaining portion of the sample is directed onto a secondcolumn containing a nonpolar liquid phase(WCOT).Benzene,toluene,and the internal standard elute in the order of theirboiling points and are detected by a flame ionization detector.Immediately after the elution of the internal standard,the flowthrough the nonpolar WCOT column is reversed to backflushthe rema