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even the constituents themselves, will vary with time and distance from <br /> the site of initial contamination due co weathering. The major <br /> component categories in automotive gasoline have been identified as the <br /> following. <br /> n-alkanas <br /> branched alkanes — <br /> cycloalkanes <br /> benzene and alkylbenzenes <br /> naphthalenes <br /> A combination of capillary column gas chromatography (GC) and gas <br /> chromatography/mass spectrometry (CC/MS) techniques may be used to <br /> identify the principal components in automotive gasoline. Fuel <br /> samples, and probably any samples collected in the field which are <br /> primarily organic in nature, may require the separation (prior to CC or <br /> GC/M5 analysis) of the aliphatic. monoaromatic and polycyclic aromatic <br /> hydrocarbon fractions using liquid solid column chromatography; the <br /> various column eivares, with or without dilution in carbon disuifida, <br /> can than be analyzed by CC or CC/MS techniques. Aqueous samples need <br /> to be liquid-liquid extracted with an appropriate solvent (i.e. , <br /> trichlorotrifluorcethans) prior to analysis; solid samples would be <br /> extracted with trichlorotrifluoroethane using soxhlet extraction or <br /> sonication methods (1422) . An aliquot of the sample extract, with or 4 <br /> without concentration, is than analyzed by. CC or CC/MS. Sampling and <br /> analysis considerations for some specific components in gasoline, i.e. , .. <br /> benzene, toluene, xylenes, ethyl ben=ens and naphthalene have been <br /> addressed in Volume 1. <br /> Alternatively. the "oil and grease' content can be measured. This <br /> determination would not be the measurement of an absolute quantity of a �`-- <br /> specific component. but rather the quantitative datermination of groups <br /> of components with similar physical characteristics (i.e. , common <br /> solubility in trichlorotrifluoroechans) . The "oil and grease" content ` <br /> is dofined as any material recovered from extraction with <br /> trichlorotrifluorcechans and measured gravimetrically; extraction <br /> methods are those described above for aqueous and soil samples. <br /> A detection limit for automotive gasoline was not determined; the <br /> detection limit for specific components is expected to be in the range <br /> of µg/L for aqueous samples and pg/g for non-aqueous samples. <br /> s <br /> 6/87 <br /> 1 ` <br />