Determination of herbicides in natural waters using solid phase microextraction (SPME) and gas chromatography coupled with flame thermionic and mass spectrometric detection

This study develops a method for solid phase microextraction (SPME) of ten widespread herbicides from water. The selected herbicides belong to different chemical groups are EPTC, molinate, propachlor, trifluralin, atrazine, propazine, terbuthylazine, prometryne, alachlor. Their determination was carried out by gas chromatography with flame thermionic and mass spectrometric detection. To perform the SPME, two types of fibre have been assayed: Carbowax-divinylbenzene (CW-DVB) of 65 mum thickness and polydimethylsiloxane-divinylbenzene (PDMS-DVB) of 65 mum thickness. The main factors affecting the SPME process such as pH, ionic strength, methanol content, memory effect, stirring rate and adsorption-time profile were studied. The method was applied to spiked natural waters such as ground water, sea water, lake water and river water in a concentration range of 0.1 to 10 mug/L. Limits of detection with each of the detectors were determined to be 1 - 20 ng/L in PDMS-DVB and 2-20 ng/L. CW-DVB fibres. The recoveries of herbicides compared to distilled water were in relatively high levels 78.3-127.3 % and the average r(2) values of the calibration curves were above 0.99 for all the analytes. The SPME conditions were finally optimized in order to obtain maximum sensitivity and samples were applied for the trace-level determination in river water samples originating from Ioannina region (Greece).