The use of stable isotopes to differentiate specific source markers for MTBE

The recent controversy over the use of MTBE within gasoline to boost oxygen content and decrease carbon monoxide emissions to the atmosphere has led t o a proposed phase-out of this compound by 2002. This paper is a preliminar y investigation into the use of gas chromatography isotope-ratio mass spect rometry (GCIRMS) to determine both carbon and hydrogen isotopic composition s of MTBE as a means of differentiating sources of MTBE. Three pure MTBE sa mples were purchased from chemical distributors. Little variation of the de lta C-13 values were observed although the samples had isotopically distinc t delta -D values. Four different methods of obtaining carbon isotope ratio s of neat MTBE, MTBE in gasoline, and MTBE in water are described, and the precision and accuracy of each is discussed. The carbon isotopic compositio ns of MTBE within 10 gasoline samples from three different areas of the Uni ted States show a wide range of carbon isotope compositions. This novel met hod of MTBE analysis could be valuable in forensic investigations. (C) 2001 AEHS.