Optimization of solid-phase microextraction conditions using a response surface methodology to determine organochlorine pesticides in water by gas chromatography and electron-capture detection.

A response surface methodology was applied to optimise the solid-phase microextraction (SPME) conditions using a polyacrylate-coated fiber to determine thirteen organochlorine pesticides from water. Analyses were performed using gas chromatography-electron-capture detection. Variables affecting absorption in both the headspace and immersion extraction were optimised by using a response surface generated with a Doehlert design, and the results were compared. The immersion SPME method was selected since higher recoveries were obtained for most of the compounds studied. The method developed was applied to the analysis of tap and Ebro river water samples. The linear range of most pesticides for real samples was found to be between 0.001 and 2.5 micrograms l-1 and the limits of detection were between 0.15 and 0.35 ng l-1. The repeatability and the reproducibility between days of the method (n = 6), expressed as relative standard deviation, for tap water spiked at a level of 1 ng l-1 were between 5.7 and 25.6% and between 7.6 and 26.5%, respectively.