The application of solid phase microextraction in the analysis of organophosphorus pesticides in a food plant

A SPME method for the determination of organophosphorus pesticide residues in a local food plant, Chrysanthemum coronarium, was established. Pesticide residues were extracted by SPME fiber (with 100 mu m poly(dimethylsiloxane ) coating) from a biphasic water/plant tissues mixture and determined by GC -FPD. An equilibrium model was derived for the system and revealed that pes ticide recoveries were related to the water:plant tissues ratio, f(r) and t he partition coefficient, K-WV, for the distribution of pesticides between the aqueous phase and the plant tissues. The model was verified by four org anophosphorus pesticides, namely phorate, diazinon, methyl parathion, and e thion. The best fitted K-WV values (P < 0.05) for the pesticides were found to be 4.73 +/- 0.32 x 10(-2) (phorate); 1.11 +/- 0.10 x 10(-1) (diazinon); 9.18 +/- 0.95 x 10(-2) (methyl parathion); and 8.21 +/- 1.28 x 10(-3) (eth ion). Remarkable correlation between the K-WV of the organophosphorus pesti cides and their octanol/water partition coefficients, K-OW, was also establ ished.