Trace Analysis of Ethanol, MTBE, and Related Oxygenate Compounds in Water Using Solid-Phase Microextraction and Gas Chromatography/Mass Spectrometry

Abstract

Solid-phase microextraction (SPME) and gas chromatography/mass spectrometry have been combined for trace-level determination of very polar compounds in water, including the widely used gasoline oxygenates ethanol and methyl tert-butyl ether (MTBE). A relatively simple extraction method using a divinylbenzene/Carboxen/poly(dimethylsiloxane) SPME fiber was optimized for the routine analysis of ethanol and MTBE in groundwater and reagent water. A sodium chloride concentration of 25% (w/w) combined with an extraction time of 25 min provided the greatest sensitivity while maintaining analytical efficiency. Replicate analyses in fortified reagent and groundwater spiked with microgram per liter concentrations of ethanol and MTBE indicate quantitative and reproducible recovery of these and related oxygenate compounds. Method detection limits were 15 μg L-1 for ethanol, 1.8 μg L-1 for tert-butyl alcohol, 0.038 μg L-1 for tert-amyl methyl ether, 0.025 μg L-1 for ethyl-tert-butyl ether, and 0.008 μg L-1 for MTBE.