| Abstract
| - An improved method is described for the routine analysisof methyl tert-butyl ether (MTBE), tert-amyl methylether (TAME), and tert-butyl alcohol (TBA) in petroleum fuel-contaminated groundwater samples using solid-phasemicroextraction (SPME) and deuterated internal standardscombined with gas chromatography mass spectrometry (GC-MS). Factors affecting method performance (SPMEfiber selection, headspace or liquid extraction, extractiontime, calibration conditions, salt addition, method sensitivity,and matrix effects) are evaluated using groundwatersamples from a chalk aquifer contaminated with petroleumfuel containing MTBE, TAME, and TBA. The detectionsensitivity and analytical efficiency of the method wasoptimized for these compounds using a PDMS-Carboxenfiber, sample NaCl content of 25% (w/v), and extraction timeof 30 min. Internal calibration standards (deuteratedMTBE and TBA) are necessary to control extraction errorsduring analysis. SPME extraction efficiency and detectionsensitivity for the oxygenates and TBA decreased asthe background matrix concentration of benzene, toluene,ethylbenzene, and xylenes (BTEX) increased up to 300mg/L total BTEX. However, reliable measurement of MTBE,TAME, and TBA was possible in this BTEX matrix usingdeuterated internal standards. The precision, accuracy, andreliability of the method were verified by analysis ofcertified standards. Analytical accuracy, determined fromreplicate (n = 10) analysis of spiked laboratory standardsand groundwater samples, was 97%, with a precision of 1.6−2.9% for MTBE, 3.1−5.8% for TAME, and 1.6−1.7% forTBA. Method detection limits under the conditions describedare 2 μg/L for TBA (by liquid sampling) and 1 μg/L forMTBE and TAME (by headspace sampling). This sensitivitycan be increased for MTBE by further refinement of themethod.
|
