Determination of benzene, toluene, ethylbenzene, xylenes in water at sub-ng l−1 levels by solid-phase microextraction coupled to cryo-trap gas chromatography–mass spectrometry

A trace analytical method of benzene, toluene, ethylbenzene and xylenes (BTEX) in water has been developed by using headspace solid-phase microextraction (HS-SPME) coupled to cryo-trap gas chromatography–mass spectrometry (GC–MS). The chromatographic peak shape for BTEX was improved by using cryo-trap equipment. The HS-SPME experimental procedures to extract BTEX from water were optimized with a 75 μm carboxen/polydimethylsiloxane (CAR/PDMS)-coated fiber at a sodium chloride concentration of 267 g l−1, extraction for 15 min at 25 °C and desorption at 290 °C for 2 min. Good linearity was verified in a range of 0.0001–50 μg l−1 for each analyte (r2 = 0.996–0.999). The limits of detection (LODs) of BTEX in water reached at sub-ng l−1 levels. LODs of benzene, toluene, ethylbenzene, m/p-xylene and o-xylene were 0.04, 0.02, 0.05, 0.01 and 0.02 ng l−1, respectively. The proposed analytical method was successfully used for the quantification of trace BTEX in ground water. The results indicate that HS-SPME coupled to cryo-trap GC–MS is an effective tool for analysis of BTEX in water samples at the sub-ng l−1 level.