METHOD FOR DETERMINATION OF METHYL TERT-BUTYL ETHER AND ITS DEGRADATION PRODUCTS IN WATER

An analytical method is described that can detect the major alkyl ethe r compounds that are used as gasoline oxygenates (methyl tert-butyl et her, MTBE; ethyl tert-butyl ether, ETBE; and tert-amyl methyl ether, T AME) and their most characteristic degradation products (tert-butyl al cohol, TBA; tert-butylformate, TBF; and tert-amyl alcohol, TAA) in wat er at sub-ppb concentrations. The new method involves gas chromatograp hy (GC) with direct aqueous injection (DAI) onto a polar column via a splitless injector, coupled with detection by mass spectrometry (MS). DAI-GC/MS gives excellent agreement with conventional purge-and-trap m ethods for MTBE over a wide range of environmentally relevant concentr ations. The new method can also give simultaneous identification of po lar compounds that might occur as degradation products of gasoline oxy genates, such as TEA, TBF, TAA, methyl acetate, and acetone. When the method was applied to effluent from a column microcosm prepared with c ore material from an urban site in New Jersey, conversion of MTBE to T BA was observed after a lag period of 35 days. However, to date, analy ses of water samples from six field sites using the DAI-GC/MS method h ave not produced evidence for the expected products of in situ degrada tion of MTBE.