SPME of 52 pesticides and polychlorinated biphenyls: Extraction efficiencies of the SPME coatings poly(dimethylsiloxane), polyacrylate, poly(dimethylsiloxane)-divinylbenzene, Carboxen-poly(dimethylsiloxane), and Carbowax-divinylbenzene

Abstract

Fiber/water partition coefficients (Kfw) of 52 pesticides, including triazines, organophosphorus pesticides, organochlorine pesticides, and polychlorinated biphenyls (PCBs) were experimentally calculated for the five polymeric coatings poly(dimethylsiloxane) (PDMS), polyacrylate (PA), poly(dimethylsiloxane)-Divinylbenzene (PDMS-DVB), Carboxen-poly(dimethylsiloxane) (CAR-PDMS), and Carbowax-divinylbenzene (CW-DVB) commercially available for solid-phase microextraction coupled to gas chromatography. The equilibrium-time profiles for the five coatings were previously studied in order to establish the time needed for equilibrium. To calculate Kfw the amount of analyte extracted at equilibrium was obtained by gas chromatographic analysis of spiked water samples. In the case of mixed coatings in which adsorption processes are involved the term partition coefficient is not strictly correct and partition coefficient apparent is used in these cases. For the triazines, small partition coefficients were found, showing that PDMS-DVB permits the best extraction for these compounds. PA and PDMS-DVB gave the highest mean partition coefficients for the organophosphorus pesticides. Organochlorine pesticides in general gave high Kfw with all five coatings, with strong differences depending on the compound. In the case of PCBs a decrease in the partition coefficient with the increase of the number of chlorines substituted was observed. The results obtained indicated that the polarity of the fibers is not the main factor affecting the extraction. The presence of DVB in the mixed coatings seems to increase the uptake, probably due to adsorption processes instead of absorption. In general the PDMS-DVB coating proved to be a good choice for the analysis of the compounds under study.