Study On Liquid Phase Microextraction Based On The Ionic Liquid And Their Applications For Determination Of Environmental Endocrine Disrupting Compounds

Environmental endocrine disrupting compounds are chemicals that can interfere with the endocrine system through mimicking natural hormones, inhibiting the action of hormones, or altering the normal regulatory function of the immune, nervous, and endocrine systems. Endocrine disrupting compounds mainly come from manufactured goods such as plastic, pesticide, preservative, detergent. Until now, many kinds of endocrine disrupting compounds including estrogen, herbicide and alkylphenol have been found in the environmental water. As a result, It is important to establish a sensitive and selective analytical method for their determination.Due to the low concentrations of endocrine disruptors in environmental samples, preconcentration is needed prior to analysis. Liquid phase microextraction, depending on the advantages in high effecency, low cost and simple operation, it attacts more and more attention as a novel enrichment technique. Additonally, when combined with ionic liquid which is known as a wonderful substitute for traditional organic solvents, the development of liquid phase microextraction become much more brighter. In this article, the ionic liquid are employed in the enrichmment technique, including single-drop microextraction, dispersive liquid phase microextraction and three-phase electroextraction, combined with high performance liquid chromatography, we established serveal feasible methods for enrichment and determination of typical endocrine disruptors in environmental water. The dissertation makes up of four parts:Chapter 1. IntroductionIn this chapter, the characteristics of endocrine disruptors were introduced. The development, the principle and applications of liquid phase microextraction were outlined. The goal and significance of this dissertation are introduced. Chapter 2. Determination of endocrine disruptors in environmental water by single-drop microextraction and high-performance liquid chromatographyUsing the single-drop microextraction followed by high performance liquid chromatography, an effective method for rapid selection or design of appropriate extractants for two species of endocrine disruptors, including estrogen and alkylphenol, was explored. In the research, six traditional solvents including tuluene, benzene, cyclohexane, isooctane, n-octane and n-octanol are chosen as extractant. Factors that influenced the extraction efficiency, such as hydrogen bonding, hydrophobic property, polarity, and van der Waals forces, were evaluated in detail. Finally, an effective method for rapid selection of extractant for different typies of endocrine disruptors is established. The results indicated that bisphenol A and estrogens were extracted effectively by the solvents with hydrogen bond acceptors and higher polarity; alkylphenols preferred solvents that could supply strong van der Waals forces or possessed π-π stacking structures and superior hydrophobicity. The optimum extraction conditions were determined, including extraction time, pH, and salt effects. Under the optimized conditions, high extraction factors (>147) were achieved. Limits of detection for the endocrine disruptors were between 0.33 and 0.67 μg L-1. The method strategy is well suited for the determination of trace levels of endocrine disruptors in environmental water.Chapter 3. Determination of three estrogens and bisphenol A by functional ionic liquid dispersive liquid phase microextraction coupled with ultra performance liquid chromatography-ultraviolet detectionA new synthetic hydroxyl-functional ionic liquid, 1-hydroxyethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, was employed in the improved dispersive liquid phase microextraction method coupled with ultra performance liquid chromatography for enrichment and determination of three estrogens and bisphenol A in environmental water samples. The introduced hydroxyl group acted as the H-bond acceptor that made the IL effectively dispersed in the aqueous phase without dispersive solvent or external force. Fourier transform infrared spectroscopy indicated that the hydroxyl group of the cation of IL enhanced the combination of extractant and analytes through the formation of H-bonding. The main parameters including volume of extractant, temperature, pH and extraction time were investigated. The calibration curves were linear in the range of 5.0-1000 μg L-for estrone, estradiol and bisphenol A; 10.0-1000μg L-1 for estriol. The detection limits were in the range of 1.7-3.4 μg L-1. The extraction efficiency was evaluated by enrichment factor which were between 85 and 129. The proposal method was proved to be a simple, low cost and environment-friendly method for determination of the four endocrine disruptors in environmental water sample.Chapter 4. Determination of chlorophenoxy acid herbicides in environmental water by Electrical field-induced three phase extraction coupled with high performance liquid chromatorigraphyCoupled with impoved electrical field-induced three phase extraction technique, a HPLC method was developed for the perconcertation and determination of chlorophenoxy acid herbicides in environmental water. In the proposed extraction, ionic liquid is introduced as a novel electrolyte in the acceptor phase and triethylamine is employed as the Lewis base to ensure a complete ionization of target molecule. After enrichement, the acceptor phase including analytes is determined by chromatographic technique. The results shows a satisfied enrichment effeciency and the calibration curves were linear in the range of 5.0-1000μg L-1 for 2-methyl-4-chlorophenoxyacetic acid; 10.0-1000μg L-1 for 2-(2, 4-Dichlorophenoxy)propionic acid. The standard deviation is less than 3.5%. The results prove that the proposed three-phase electroextraction is a novel, effective method for perconcertration of analytes with low ionized degree from water sample.