DETERMINATION OF THE SEMIVOLATILE COMPOUNDS NITROBENZENE, ISOPHORONE, 2,4-DINITROTOLUENE AND 2,6-DINITROTOLUENE IN WATER USING SOLID-PHASE MICROEXTRACTION WITH A POLYDIMETHYLSILOXANE-COATED FIBER

Aqueous samples of the semi-volatile compounds nitrobenzene, isophorone, 2,4-dinitrotoluene and 2,6-dinitrotoluene, listed in the US Environmental Protection Agency (EPA) Method 609, were analysed by solid-phase microextraction (SPME) with a polydimethylsiloxane-coated fibre. SPME is a technique to extract organics from an aqueous matrix into a stationary phase immobilized on a fused-silica fibre. The analytes are thermally desorbed directly into the injector of a gas chromatograph. The sensitivity of this method decreased with increasing concentration of methanol and absorption temperature and increased with increasing concentration of Na2SO4. Samples of lake water were analysed using calibration graphs based on deionized water. The relative standard deviations of these analytes were 1-2% for analytes in deionized water and 2-4% for analytes in lake water. The detection limits were 9 ng/ml for nitrobenzene and 15 ng/ml for the other three analytes.