Application of solid phase micro-extraction (SPME) to the analysis of pesticide residues in vegetables

Solid Phase Micro-Extraction (SPME) is a new analytical technique, based on capturing the analytes by adsorption onto an organic phase coating a glass fibre, and subsequent direct desorption into the injector of a gas chromat ograph. This technique has been successfully applied in the analysis of org anic contaminants in water, giving linear responses and, in some cases, hig h sensitivities. The present paper reports data about the application of SPME to the analysi s of pesticide residues in a vegetable matrix, testing over nearly one hund red active compounds, with two types of adsorbent phase (polydimethylsiloxa ne and Carbowax/divinylbenzene). A vegetable matrix spiked with pesticides was analyzed by SPME and by a traditional multi-residue method; recoveries were determined and compared for the two cases. The behaviour of the analyt ical response by SPME was studied in the range 0.01-1mg kg(-1) by adding in creasing amounts of given pesticide mixtures to the vegetable matrix. The procedure was further tested by analyzing real samples, and gave some d ifficulties in recovering the whole amount of some of the residues present (in comparison with the traditional method). The SPME method was then impro ved by pre-extracting with acetone and sonicating before the extraction/ads orption step. The results obtained were satisfactory (some certified matric es were also tested) with good accordance between the two methods. Neverthe less some active compounds showed very low responses or remained undetectab le by SPME in our experimental conditions. (C) 2000 Society of Chemical Ind ustry.