| The content of the organic pollutants always exist at trace levels in real water samples. Despite advances in instrumental techniques, complete non-invasive measurements are still not possible in most cases. Thus, development of extensive sample preparation and preconcentration methods is necessary prior to instrumental analysis. Traditional sample preparation methods are tedious, labor-intensive and time-consuming, and consume large quantities of potentially toxic and expensive high-purity solvents. Along with the trend in miniaturization in analytical chemistry, microextraction methods have undergone rapid development. Liquid phase mixcroextraction(LPME) is a fast, simple, and green sample preparation technique that combines preconcentration and sampling into one step, and can be applied to extract trace organic pollutants from real water samples.1. A new sample treatment, namely vortex-assisted ionic liquid dispersive liquid-liquid microextraction(VA-IL-DLLME), followed by high-performance liquid chromatography has been developed for the determination of five organic UV filters. The ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate was used as extraction solvent. Various parameters that affected the extraction efficiency(such as volume of extraction solvent, type and volume of disperser solvent, vortex time, centrifugation time, type and volume of dilution solvent, and sample pH) were evaluated. Under the optimum conditions, the linearities were between 4 and 1000 ng/mL for 2, 4-dihydroxybenzophenone, 3.5 and 1000 ng/mL for 2-hydroxy-4-methoxybenzophenone, 10 and 1000 ng/mL for benzophenone, ethylhexyl salicylate and homosalate with the correlation coefficients from 0.9925 to 0.999; The limits of detection were in the range of 0.8~2.8 ng/mL, and relative standard deviations below 7.8 %. Finally, the proposed method was successfully applied to different real water samples and acceptable relative recoveries over the range of 55.8~118.9% were obtained.2. A new disperser solvent-free dispersive liquid phase microextraction method named vortex-assisted elevated temperature ionic liquid dispersive liquid phase microextraction followed by high performance liquid chromatography was developed for the extraction, preconcentration and determination of five organic ultraviolet filters(2,4-dihydroxy benzophenon, benzophenon, 2-hydroxy-4-methoxy benzophenone,2-ethylhexyl salicylate and 3,3,5-trimethyl cyclohexyl salicylate). The temperature of aqueous phase was adjusted by elevated temperature and then an extraction solvent was rapidly injected into the aqueous phase and vortexed it. After cooling to room temperature, the phase separation was accelerated by centrifugation. Elevated temperature and vortex-assisted process were applied to assist the formation of the fine cloudy solution, without use of disperser solvent. Various parameters affecting the extraction efficiency, such as volume of the extraction solvents, extraction time, temperature, centrifugation time, type and volume of the dilution solvents, pH of sample solution were evaluated and optimized. Under the optimum conditions, the linear ranges were between 2.8 and 1000 ng/mL with correlation coefficients ranging from 0.9943 to 0.9997; The method resulted in low limits of detection(0.7 ~ 1.8 ng/mL) and quantification(2.3 ~ 6.2 ng/mL) and good repeatability(RSDs% below 7.5). The proposed method was successfully applied to the determination of UV filters in swimming pool and tap water samples with relative recoveries ranged from 85.6% to 108.7%.3. Comparisons between the VA-IL-DLLME-HPLC and the VA-ET-IL-DLPME-HPLC for the determination of the UV filters. In comparison with VA-IL-DLLME-HPLC, the linear ranges and LODs for VA-ET-IL-DLPME-HPLC are better. |
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