Application of chemometric techniques to the optimization of the solid-phase extraction of 27 pesticides before GC-MIP-AES analysis

Determination of heteroelement organic compounds at environmental levels re quires highly efficient chromatographic separations and selective and sensi tive detection. For this purpose, a capillary gas chromatographic-helium at mospheric pressure microwave-induced plasma atomic emission detection metho d was developed for the simultaneous determination of 18 organochlorine and nine organophosphorus pesticides in water samples. Monitoring the emission lines for elements such as chlorine, phosphorus and sulfur ensures nearly specific chromatograms for these elements, increasing the selectivity marke dly. On the other hand, to allow quantitative recoveries of these pesticide s from aqueous samples, the solid-phase extraction (SPE) of the target comp ounds was optimised using two sequential experimental designs. A 2(3) facto rial design was initially performed to study the relative importance of thr ee SPE main variables: sample volume, volume and percentage of dichlorometh ane in the elution solvent. Following this factorial design, a central comp osite design was used to demonstrate that the SPE conditions can be optimis ed to obtain the best overall recoveries of the 27 compounds studied. The e xtraction and determination techniques were applied to the determination of pesticides in waste water samples.