Optimization and comparison of membrane-protected micro-solid-phase extraction coupled with dispersive liquid-liquid microextraction for organochlorine pesticides using three different sorbents

A micro-solid-phase extraction technique has been developed, for determination of organochlorine pesticides in water media, using gas chromatography-electron capture detector. Response surface methodology was applied to optimize the performance of the extraction technique. Also, the effect of significant experimental parameters (Le. extraction time, ionic strength, type and volume of the desorption solvent and desorption time) has been studied. Three frequently used solid sorbents; multi-walled carbon nanotube, silica-based C18, and polymeric solid sorbent (LiChrolut (R) EN), were implemented and independently optimized and the results were compared to find the best extraction setup. A dispersive liquid-liquid extraction procedure was also used to enhance the sensitivity of the method, showing enrichment factors of 14 to 40. The limits of detection of the optimized technique were less than 0.26 mu g L-1 (for methoxychlor with C18) and RSD values were between 3.3 and 14.5% at 1 mu g L-1. The calibration functions were linear up to 500 mu g L-1 with R-2 values of more than 0.995, for all sorbents. The figures of merit of the entire procedure showed that each of the studied sorbents could produce satisfactory results in ultra-trace determination organochlorine pesticides in water.