Optimization of headspace solid-phase microextraction conditions for the determination of organophosphorus insecticides in olive oil

A method based on headspace solid-phase microextraction (HS-SPME) technique followed by gas chromatography with flame thermionic detection was developed for the determination of seven organophosphorus (OP) insecticide residues in olive oil samples. The extraction capacity of four fiber coatings, polyacrylate (PA 85 mum), poly(dimethylsiloxane) (PDMS 100 mum), carbowax-divinylbenzene (CW-DVB 65 mu m) and poly(dimethylsiloxane)divinylbenzene (PDMS-DVB 65 mum), have been studied and compared. The method was developed using spiked olive oil samples in the concentration range 0.025 to 0.5 mg/L. The PDMS 100- mum fiber showed good extraction efficiency for the target compounds. An increase in the extraction efficiency of OP insecticides was observed when the parameters affecting the HS-SPME process such as temperature, extraction time, salt additives and stirring rate were optimized. Good linearity was observed for the compounds in the tested concentration range. The limits of detection were between 0.005 and 0.01 mug/L.