High levels of monoaromatic compounds limit the use of solid-phase microextraction of methyl tert-butyl ether and tert-butyl alcohol

Recently, two papers reported the use of solid-phase microextraction (SPME) with poly(dimethylsiloxane)(PDMS)/Carboxen fibers to determine trace levels of methyl tert-butyl ether (MTBE) and tert-butyl alcohol (tBA) in water. Attempts were made to apply this technique to the analysis of water samples containing high levels of benzene, toluene, ethylbenzene, xylenes, and trimethylbenzenes (BTEXsTMBs) as would be expected at leaking underground storage tank sites. It was found that when the sample contained total aromatic compounds above 1 ppm, the response of the internal standards, deuterated MTBE and tBA, dropped by more than 65%. As this decrease in internal standard peak area was unacceptable, a static headspace method was used instead. This headspace method was used successfully to analyze groundwater from 670 monitoring wells at 74 service stations located in the northeast United States. In these monitoring wells, 30% of the samples contained total BTEXsTMBs above 1 ppm. If the SPME method was used to analyze these samples, dilution of more than 200 samples would be required to minimize the adverse matrix effect that high aromatic content had on the internal standard peak area.