Application Study Of Hollow-fiber Liquid-phase Microextraction Combined With Capillary Electrophoresis On Trace Pollutant Analyses

1. PrefaceCapillary electrophoresis (CE), which has been developed rapidly with the advantages such as rapid analysis, automation, broad application and low cost, is a new separation and analysis technique. Currently, this analytical technique is widely used in environmental analysis, food analysis and pharmaceutical research areas of clinical analysis, nucleic acids and proteomics research. This chapter briefly introduces an overview of capillary electrophoresis (including the basic principles, different separation modes, various detection methods), the new progress of liquid phase microextraction technology (including its principles and applications), as well as the new progress of the application of CE in water analysis. In addition, this chapter also summarizes the purpose and significance of this thesis. Hollow-fiber liquid-phase microextraction (HF-LPME) with high purification and enrichment combined with high efficiency of CE, and high selectivity and sensitivity of AD, is the main technology employed in this thesis. In particular, the determination of trace environmental contaminants in water samples with the help of HF-LPME/CE-AD was discussed.2. Simultaneous determination of phenolic endocrine disruptors in water samples by CE coupled with hollow-fiber liquid-phase microextractionHollow-fiber liquid-phase microextraction coupled with capillary electrophoresis amperometric detection has been developed for simultaneous determination of nine environmental endocrine disruptors, including bisphenol A, methylparaben, ethylparaben, propylparaben,4-tert-butylphenol, diethylstilbestrol, 17a-ethinylestradiol,β-estradiol and estriol. In this work, various experimental parameters affecting enrichment factors, electrophoretic separation and detection were investigated in detail. And poly (sodium 4-styrenesulfonate) was selected as the buffer modifier, resulting in considerable improvement of the separation efficiency of the target analytes. Under the optimum conditions, nine analytes could be well separated within 30 min in a 10 g/L poly (sodium 4-styrenesulfonate) modified 60 mmol/L Na2B4O7-H3BO3 buffer (pH 7.60). Each analyte could obtain good linear correlation between electrochemical response and its concentration at two or three grades, the method detection limits could reach 0.047-13 ng/mL (S/N=3) with the assistance of hollow-fiber liquid-phase microextraction, and the highest enrichment factor could be up to 255-fold. This proposed method has been applied for the direct analyses of real environmental water and tap water samples, the average recoveries were in the range of 81.4-117%, and the corresponding relative standard deviations were lower than 6.2%. This approach is expected to provide a new alternative method for the trace analysis of phenolic endocrine disruptors in environmental water samples, because of its high sensitivity and no need of derivatization.3. Hollow-fiber liquid-phase microextraction coupled with miniaturized capillary electrophoresis for the trace analysis of four aliphatic aldehydes in water samplesA novel miniaturized CE with amperometric detection (mini-CE-AD) method has been established for fast determination of four low molecule aliphatic aldehydes, namely formaldehyde, acetaldehyde, propylaldehyde and butyraldehyde, in water samples. On the basis of our previous research work, we select an electroactive compound 2-thiobarbituric acid as derivatization reagents, and after derivatization these non-electroactive aldehydes were converted to electroactive adducts, which can be detectable by mini-CE-AD. Under the optimum conditions, four aldehydes can be well separated with the coexisting interferents as well as their homologs (such as methyl-glyoxal and glyoxal), and the limits of detection (S/N=3) were achieved at nanogram-per-milliliter level based on HF-LPME. The proposed approach has been applied in different real water samples including tap water, river water, drinking water, and the average recoveries were in the range of 90%-113%, which is expected to a potential new way to fast analysis of low molecule aliphatic aldehydes in water samples.