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Detection and fate of pharmaceutical compounds and personal care products in the environment

Tsourounaki Kostoula

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Summary

In the present thesis, different novel, powerful and “green” analytical protocols used for rapid and accurate measurement of trace amounts of insect repellents and parabens in various aqueous matrices. The detection of these pollutants was carried out using the solid phase micro-extraction (SPME) and liquid phase micro-extraction (LPME). The study of the photolytic fate of these compounds was monitored in various aqueous environmental matrices in order to determine the rates of decomposition and the effect of environmental matrix in the process of photolysis.More specifically, in chapter 1 of this thesis a brief overview of basic sample preparation techniques and a more detailed description in the hollow fiber liquid phase microextraction (HF-LPME) and SPME is discussed. The various degradation mechanisms and kinetics, that pollutants may follow in the environment are also reported.In chapter 2, the applicability of three phase HF-LPME coupled to liquid chromatography- multiple wavelength detector for the extraction of four parabens (methyl-, ethyl-, propyl- and butyl- paraben) from environmental water samples is demonstrated.Parameters such as extraction solvent, volume and pH of donor and acceptor solution, agitation speed of the aqueous sample and sampling time were controlled and optimised. Target analytes were extracted for 30 min from 14 mL of aqueous samples adjusted to pH 6 (donor solution) stirred at 1000 rpm through a thin phase of 1-octanol inside the pores of a 5.5 cm polypropylene hollow fiber and finally into a 18 μL basic acceptor solution placed in the lumen of the hollow fiber. The method provides isolation and preconcentration of the analytes as well as a final extract compatible with LC analysis without additional purification.The calculated calibration curves gave a high level of linearity for all target analytes in the range of 0.5-1000 μg L−1 with correlation coefficients higher than 0.9955. The repeatability of the proposed method, expressed as relative standard deviation varied between 1.6 and 7.0 % (n = 5) and 3.5 and 8.9 % (n = 5) for 10 and 100 μg L−1, respectively. The limits of detection were in the low μg L−1 concentration level. The applicability of the developed HF-LPME was demonstrated for real water samples. In particular, three different water samples originating from baby bathwater were analysed.In addition, the simplicity of the device and the low consumption of organic solvents made this method a cheap, green and easy procedure opening new pathways in environmental analysis.In chapter 3, the present thesis investigated the degradation of four parabens in ultrapure, natural waters and treated wastewater subjected to ultraviolet irradiation (16 W, 254 nm). The effect of operating conditions such as initial concentration and pH on the photodegradation of the parabens was studied. The results indicated that under direct photolysis with monochromatic light at 254 nm, nearly complete photoremoval of parabens (10 μg mL-1) could be achieved within 90 min of irradiation and the photochemical rates followed pseudo first-order kinetics. The removal of parabens was accelerated faster at pH 5 rather than at pH 7 and 11. The effect of important constituents of natural waters: (i.e. humic acids (HA) and nitrate ions) was also investigated the results showed that both of them act as filters in the aqueous photolysis of parabens. The presence of salt (NaCl) and 1-butanol in the ultrapure water solutions was also investigated on the degradation. 1-butanol as radical scavenger was found not to affect the photolytic rates of parabens, but the salt had a minor effect on target analytes. The environmental waters inhibited the photodegradation of parabens compared to ultrapure water. The inhibition followed the order of river water < treated wastewater < seawater. The photodegradation of parabens employing ultraviolet (UV) irradiation may emerge as a viable method for the future because of its cost efficiency.In chapter 4, the photodegradation of two insect repellents (di-n propylisocinchomeronate, R-326 and bytyl-3.4-dihydro-2.2-dimethyl-4-oxo-2H-pyran-6-carboxylate, butopyronoxyl) was investigated under UV irradiation in river water, treated sewage as well as in ultrapure water. The SPME coupled to mass spectrometry - gas chromatography was used to monitor a trace amounts of insect repellents. Several parameters, that influence the kinetics of degradation were assessed as the effect of the initial concentration of insect repellents and certain environmental factors, including sodium chloride and potassium nitrate. The effect of 1-butanol (radical scavenger) in the degradation process of the insect repellents was also studied It was found that photodegradation proceeds via a pseudo-first order reaction and that the degradation amount in the presence of nitrate ions and 1-butanol is not significantly affected. Degradation rate of butopyronoxyl was enhanced by the presence of sodium chloride salt, unlike, the degradation rate of R-326 decreased. Investigations on river and treated wastewater samples spiked with R-326 revealed that photolysis is enhanced in the order river > treatment wastewater.To the best of our knowledge the present work represents the first attempt to characterize the photochemistry of R-326 and butopyronoxyl, and as such some points need much more study. At this stage of the study our efforts were most focused on determining the mechanisms of decomposition and the effect of environmental matrix on the process of photolysis and not to identify the possible products formed. In summary, the use of SPME constitutes a powerful tool that clearly simplifies monitoring of photo-transformation processes.In chapter 5 of this thesis, conclusions and proposals for future investigation are presented.

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