Novel Sample Preparation Coupled With Capillary Electrophoresis For The Separation And Determination Of Environmental Pollutants

It is really imperative to pretreat the analytes in the environmental matrix for the fact that the environmental pollutants is in complicated matrix and trace levels. The sample pretreatment can effectively concentrate and purify the environmental samples. Liquid liquid extraction(LLE) and solid phase extraction(SPE) are two types of traditional and classical pretreatment techniques, however they have the disadvantages such as operation complicated, time consuming and use a lot of toxic organic reagents, which will bring heavy damage to the environment and human health. Dispersive liquid-liquid microextraction(DLLME) and dispersive solid-phase extraction(dSPE) are two types of novel pretreatment techniques based on the LLE and SPE. The two methods have developed quickly and been applied in various fields for their advantages of simplicity, speediness and high efficiency, which have attracted extensive attention.Capillary electrophoresis(CE) is a relatively mature technique used for separation and analysis. It is widely used in variety of fields such as environment, medicine and food for its prominent advantages of fast analysis speed,low solvent consumption and high degree of automation. In our study, the novel sample pre-treatment techniques coupled with capillary electrophoresis were adopted for the analysis of environmental pollutants in the water samples and we further investigate the on-line concentration technique for the determination of phenolic environmental estrogens(PEEs). The main research contents of the thesis were as follows:In chapter 1, two types of novel sample pretreatment techniques of DLLME and dSPE were introduced. The basic theories, the separation modes and on-line concentration technique of CE were also reviewed. The meaning and intent of this research paper were indicated.In chapter 2, dispersive solid-phase extraction followed by capillary electrophoresis(dSPE-CE) was developed for the determination of mercury speciation in environmental water samples. The synthetic material of sulfydryl-functionalized SiO2 microspheres(SiO2-SH) was firstly used as dSPE adsorbent along with L-cysteine(L-cys) containing hydrochloric acid as elution reagent. Characterization of the material was confirmed by scanning electron microscopy(SEM). Several dSPE parameters affecting the extraction efficiency were optimized, including sample pH, the amount of adsorbent, volume of eluent and concentration of hydrochloric acid. Under the optimal conditions, good linearity in the range of 2-200 ug/L for methylmercury, phenylmercury and 4-200 ug/L for ethylmercury was achieved. The limits of detection(LOD) and limits of quantitation(LOQ) for the analytes obtained were 0.24-1.07μg/L and 0.79-3.57 μg/L with enrichment factor(EF) ranging from 109 to 184. Recoveries were determined with tap water and lake water in the range of 62.3%-107.2%, with corresponding RSDs of 3.5–10.1 %.In chapter 3, dispersive liquid-liquid microextraction coupled with capillary electrophoresis(DLLME-CE) was successfully developed for simultaneous determination of four types of phenolic environmental estrogens(PEEs), namely hexestrol(HS), bisphenol A(BPA), diethylstilbestrol(DES) and dienestrol(DS). Several parameters affecting DLLME and MEKC conditions were investigated. Under the optimal conditions, enrichment factors of 241-467, as well as LODs of 0.3-0.6 ?g/L were obtained. The DLLME-MEKC method has been successfully applied in the real water samples of tap water, lake water and seawater with the recoveries ranging from 70.4 to 108.1% and RSDs in the range of 2.1–9.7%.In chapter 4, the on-line concentration technique of pressure-assisted electrokinetic injection(PAEKI) was adopted for enrichment and determination of four types of phenolic environmental estrogens(PEEs) based on micellar electrokinetic chromatography. Several parameters affecting enrichment effects such as injection voltage, injection time were optimized, and further compared with the usual injection. Under the optimal conditions, the LODs in the range of 0.0071-0.017 mg/L were obtained, as well as enrichment factors ranging from 11 to 15.