Simultaneous determination of trihalomethanes and organochlorine pesticides in water samples by direct immersion-headspace-solid phase microextraction

In this study the extraction conditions for the simultaneous extraction of volatile (trihalomethanes - THM) and semi-volatile (organochlorine pesticides) compounds from water samples by direct immersion-headspace-solid phase microextraction (DI-HS-SPME) were optimized and compared. The extraction efficiencies of the proposed DI-HS-SPME and traditional SPME modes were also compared. The separation and detection were performed by gas chromatography-mass spectrometry in SIM mode (GC-MS-SIM). The variables evaluated were extraction time, extraction temperature and added volume of aqueous NaCl solution at 20% (m/v). Central composite designs were carried out to determine the optimal extraction conditions for each SPME mode. The optimal condition for the DI-HS-SPME mode was 80 min of total extraction time (64 min at 70 °C in DI-SPME mode and 16 min at 12 °C in HS-SPME mode) with 5 mL of 20% (m/v) NaCl solution. The SPME extraction modes were compared and the DI-HS-SPME produced excellent results for both volatile and semi-volatile compounds. This represents a promising alternative for the analysis of matrices that contain compounds with very different ranges of volatility. The analytical figures of merit were evaluated and good results were obtained using this procedure for both classes of compounds studied. The limit of quantitation ranged from 0.02 to 2.0 μg L−1 for organochlorine pesticides and from 0.30 to 0.77 μg L−1 for THM.