Analysis of pesticides volatilised from plants and soil by headspace solid-phase microextraction and gas chromatography

Pesticides volatilised from plants and soil were determined by headspace SP ME and gas chromatography with electron-capture and mass spectrometric dete ction. SPME analyses were carried out with polydimethylsiloxane (PDMS) and polyacrylate (PA) fibres. A mixture of endosulfan, chlorpyrifos, lindane an d pendimethalin was used in these assays. Fortified soil and plant samples were maintained at 30 degreesC, for 2 h and 1 h, respectively, before SPME sampling. Pesticides were extracted by SPME by inserting the sheathed fibre through the cap and exposing it to the headspace for 1 h. GC-ECD analysis was performed after thermal desorption of pesticides from t he fibre for 5 minutes. Pesticide identity was confirmed by mass spectromet ry operating in the electron impact mode (El). The SPME fibres assayed gave good results, the response obtained with the PDMS fibre being somewhat bet ter in the concentration range studied. Detection limits for the compounds studied varied from 1 to 8 ng L-1.