HOLLOW FIBRE LIQUID PHASE MICROEXTRACTION OF SELECTED ORGANOCHLORINE PESTICIDES

摘要

An analytical method that combines hollow fibre liquid phase microextraction (HF-LPME) coupled to gas chromatography-electron capture detection (GC-ECD) for the analysis of organochlorine pesticides (OCPs) in water has been develop and optimised. The pesticides considered are two organochiorine insecticides (namely: endosulfan A and endosulfan B), one pyridine organothiophosphate insecticide (chloropyriphos), and one organochlorine bridged diphenyl acaricide (dicofol). These chemicals are known to disrupt the hormone endocrine system and induce cancer in a range of organisms, thereby posing a significant risk to natural ecosystems and human health. OCPs have a very low solubility in water, are fat soluble, resist metabolic degradation and have a propensity to bioaccumulate in the food chain. Monitoring pesticide residues in waters is important for human health protection and environmental control. Liquid phase microextraction (LPME) represents a miniaturization of the traditional liquid-liquid extraction LLE method and is an attractive, efficient and cost-effective alternative sample preparation method when compared to conventional or recently introduced preconcentration methods. It requires the use of microvolumes of organic solvent to extract analytes from only few milliliters of aqueous samples. Hollow-fiber LPME takes advantage of the protective future of a hollow fiber segment and as such together with extraction microfiltration and matrix appears to have an insignificant effect upon preconcentration in the majority of cases. Over the past ten years various applications dealing with the application of this novel mean of sample preparation to a wide variety of sample matrices (e.g. Water, soil, food, biological) containing trace amounts of pollutants (organic as well as metals). Experimental parameters affecting the extraction of the studied pesticides such as selection of organic solvent, agitation, extraction time, sample volume, fiber length, addition of sodium chloride, effect of pH and temperature were optimised. A half-fractional factorial design, for six variables at two levels, 2~6-1, was applied supported by an analysis of variance (ANOVA) table, indicating which parameters have a significant effect upon extraction. Repeatability, linearity, correlation coefficient and detection limit were investigated under the optimised experimental conditions. The performance of the developed procedure was found to be very good. Quality parameters and matrix effects were evaluated by analysing spiked wastewater samples.