Microextraction techniques and isotope dilution for sensitive determination of some endocrine disruptor compounds and pesticides in different matrices by GC-MC, wastewater treatment and bioaccessibility studies

The adverse effects of micropollutants on human health and the environment at large has been of great concern for many years. Advancement in measurement technology offers scientists the advantage to detect these contaminants, but there are challenges to perform the accurate and precise determination of analytes in complex sample matrices at trace levels. This study presents different microextraction strategies based on the principles of liquid-liquid and solid phase microextraction for the separation and preconcentration of selected analytes. The study was focused on twelve principal analytes including alkyl phenols (4-n-nonylphenol, 4-n-octylphenol), bisphenol A, pesticides (heptachlor, aldrin, cis-chlordane, dieldrin, endosulfan α/β, diazinon) and hormones (estrone, 17-beta-Estradiol) for the different microextraction methods, but other analytes (triflumizole, paclobutrazole, parathion methyl) were used for specific studies. All determinations were performed with a gas chromatograph system coupled to a mass selective detector. The microextraction strategies employed in this study were dispersive liquid-liquid microextraction, switchable solvent liquid phase microextraction, binary solvent microextraction and sonication assisted binary solid phase microextraction. All extraction methods were developed by performing comprehensive optimization studies, either a univariate (step-by-step) or multivariate (experimental design) optimization. The optimum parameters of each method were used to determine analytical performance of the systems, for which increase in detection power up to about 350 folds was recorded for analytes. Accuracy and precision of the methods were tested by performing recovery studies and the appreciable results were obtained. However, the accuracy of quantitative determinations was enhanced by using matrix matching calibrations to overcome the effects of complex sample matrices such as wastewater, well water, sea water, lake water, soil and waste sludge. Quadrupole isotope dilution mass spectrometry as a superior quantitative technique was combined with dispersive liquid-liquid microextraction to obtain unprecedented accuracy and precision at trace levels. Treatment of the twelve principal analytes in wastewater was also the other topic of this thesis. Two batch type bioreactors operating at different sludge retention times were used in the treatment step. Reduction in the amounts of orthophosphate, chemical oxygen demand and ammonium established good removal efficiency, and nearly all analytes were not detected in the effluents. The migration and bioaccessibility of the analytes into plants was also studied in a soilless medium, and the transformations they undergo in the stomach and intestine were tested by simulating gastric and intestinal conditions. Microextraction strategies presented in this study are highly efficient, accurate and precise, in agreement with green chemistry and easily applicable to different sample matrices. The high sensitivity allows trace determinations which can be used to monitor wastewater effluents and biological samples such as plants for their contamination levels.