Unique Fingerprints derived from the Isotopic Composition of Individual Compounds in Complex Mixtures-Applications to Environmental Problems involving MTBE and Hydrocarbon Spills
Fingerprinting techniques such as GC and GCMS have been used extensively andrnsuccessfully in environmental problems for many years. However there are situations,rnparticularly in the case of single component spills such as PCE or TCE, or MTBE inrngroundwater where GC and GCMS are not very useful. Even in the case of gasoline spills, GCrnand GCMS may not always provide the unique fingerprint necessary to confirm the relationshiprnbetween spilled product and suspected source. The development and commercial availability ofrnthe combined gas chromatography-isotope ratio mass spectrometry system (GCIRMS) hasrngreatly improved our ability to make correlations of complex mixtures or single componentsrnbased on the isotopic composition of individual compounds in the mixtures. The approach isrnparticularly powerful for differentiating sources of single component spills, for example toluene,rnMTBE, PCE or TCE derived from different suppliers. In addition refined hydrocarbon productsrnsuch as gasoline from different sources can be discriminated on the basis of the isotopicrncompositions of individual hydrocarbons and additives.rnThe purpose of this talk will be to introduce the concept of gas chromatography-isotopernratio mass spectrometry and its application to various environmental problems, specifically thoserninvolving MTBE, refined hydrocarbon products and crude oils. Whilst it is not proposed that thisrnapproach will replace the more conventional GC or GCMS techniques, when used in conjunctionrnwith these techniques it adds another level of confidence to any correlations being made. Inrnaddition for single components it may be the only technique available for undertakingrncorrelations.
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