Application of Solid Phase Microextraction to the Analysis of Pesticides in Vegetables

Solid phase micro-extraction (SPME), a solvent-free, rapid and inexpensive method for the extraction of organic compounds from aqueous sample matrices, was evaluated for determination of the 120 pesticides in vegetables such as crown daisy, perilla leaf, leafy lettuce and to mato. The analysis conditions were chosen for the SPME method: 15 min of immersion of the PDMS fiber in 10 ml of the solution with stirring at 1,000 rpm. The recovery tests were carried out in triplicate. The range of recoveries was 0-142% for organochlorine pesticides and $4.9\sim200\%$ for organophosphorus pesticides. The recoveries were very low in the pesticide groups with low solubility in water. The recoveries became lower in proportion to the interference materials in vegetables. The recovery in tomato was relatively higher than that in perilla Ie af and crown daisy. The recovery values obtained by SPE and SPME were compared. In leaf y lettuce, recovery obtained by SPE method ranged from $58.1\%\;to\;136.1\%$ and recovery by SPME ranged from $9.6\%\;to\;176.3\%$ In organophosphorus pesticides. The recovery in SPME method was satisfactory with $136\%$ for ethoprophos, $119\%$ for methidathion and $113\%$ for diazinon. Meanwhile, recovery of EPN, phenthoate and 2,4-DDT revealed relatively low value of $38\%,\;41\%\;and\;3.4\%,$ respectively. However, most of pesticides applied to SPME method sho wed constant recovery and precision. From these results, it can be concluded that solid phase micro-extraction might be an appropriate method for the screening test of pesticides in vegetables.