Use of SPME extraction to determine organophosphorus pesticides adsorption phenomena in water and soil matrices

Solid- phase micro extraction ( SPME) coupled with GC enables rapid and simple analysis of organophosphorus pesticides in a range of complex matrices. Investigations were made into the extraction efficiencies from water of six organophosphorus insecticides ( methamidophos, omethoate, dimethoate, parathion methyl, malathion, and parathion ethyl) showing a wide range of polarities. Three SPME fibres coated with different stationary phases, polydimethylsiloxane, polyacrylate, and carbowax- divinylbenzene ( CW- DVB), were investigated. Water was spiked with the pesticides at concentrations from 1 to 0.01 mu g/mL(-1), and the solutions used for optimization of the procedure. The CW- DVB fibre, with a 65 mm coating, gave the best performance. The optimized experimental conditions were sample volume 10mL at 20 degrees C, equilibration time 16 min, pH 5, and presence of 10% w/ v NaCl. SPME analyses were performed on solutions obtained by equilibrating aqueous pesticide solutions with six certified soils with various physico- chemical characteristics. SPME data were also assessed by comparison with analyses performed by using conventional solid- phase extraction. Results indicate the suitability of SPME for analysis of pesticides in environmental water samples.