New Methods For The Separation And Determination Of Nitrophenols And Metal Ions By Capillary Electrophoresis

In the last two decades, capillary electrophoresis (CE) and capillary electrochromatography (CEC) have undergone rapid development and become one of the most powerful tools available in analytical chemistry. In this work, we focused on the study of CE relative technologies, including the preparation of novel capillary columns and the establishment of new analytic methods in order to expend the application of CE and CEC. The outlines of this thesis are listed as follows:1. A poly (4-vinylpyridine-ethylene glycol dimethacrylate) (4-VP-EDMA) monolithic solid-phase extraction (SPE) method coupled with capillary electrokinetic separation was proposed for determining trace nitrophenols (2-nitrophenol,3-nitrophenol,4-nitrophenol,2-chlorophenol and 2, 4-dichlorophenol) in water samples. The extraction device was composed by a regular plastic syringe, the poly (4-VP-EDMA) monolithic capillary tube (530μm id×3 cm) and a plastic pinhead, which connected the monolithic capillary monoltith and the syringe. In the monolithic SPE, the sample solution was loaded via the monolithic capillary bed by a syringe pump. Adsorpted analytes were then eluted by an aliquot of appropriate solution, which was collected into a vial for the subsequent analysis. The separation conditions and experimental parameters for in-tube solid-phase extraction were optimized carefully. Good linearity was obtained for all five nitrophenols with the detection limits of 0.25-0.4μg/mL. Acceptable recoveries of 82.7-108.6% were obtained in tap, snow and Yangzi River water, indicating that the method could be used for the determination of nitrophenols in real water samples.2. A poly (4-VP-EGMA) monolith was synthesized and constructed as a concentrators for in-line solid-phase extraction coupling with capillary electrophoresis. The developed concentrator was used for the determination of trace nitrophenols (2-nitrophenol,3-nitrophenol,4-nitrophenol,2-chlorophenol and 2,4-dichlorophenol) in water samples. The experimental parameters for in-line solid-phase extraction, such as composition and volume of the elution plug, pH of sample solutions and the time for sample loading, were optimized. At the optimum condition, the preconcentration factor over 1000 was achieved. Good linearity was obtained in the range from 10 to 500 ng mL-1(R2> 0.999) for all five nitrophenols with the detection limits of 1.3-3.3 ng mL-1. The recoveries of 84-105% were obtained in tap, snow and Yangzi River water spiked of 20 ng mL-1 and 200 ng mL-1, respectively. It has been demonstrated that this work has great potential for the analysis of nitrophenols in real water samples.3. An electroosmotic pump driving novel molecularly impinted monolithic capillary column was prepared and used for the CEC separation of nitrophenol isomers. After the pretreatment of capillary, an 9 cm length of silica monolith is located just behind the detection window of the capillary by sol-gel, then 4-nitorphenol (4-NP) imprinted polymer is prepared using 4-VP as a functional monomer. Using this approach, strong and steady EOF is generated by silica monolith in the 4-VP based MIP column which could not generated EOF at all. Under the voltage of 12 kV, the separation of three nitrophenol isomers is achieved and higher column efficiency is obtained compared with the separation with capillary liquid chromatography.4. A simultaneous separation of four metal ions of Cd2+, Co2+, Zn2+ and Cu2+ was developed by capillary electrophoresis using HQ3 (Bis(2-pyridylmethyl) (8-pyridylmethyloxy-quinoline-2-methyl) amine) as chelating ligand. It has been demonstrated that HQ3 plays two important roles in the simultaneous separation by CE. The first role is to improve separation selectivity of Cd2+, Co2+, Zn2+ and Cu2+ by forming metal-HQ3 complexes. Another is to make the UV detection of metal ions possible with high UV sensitivity. The separation conditions have been optimized. The baseline separation of Cd2+, Co2+, Zn2+ and Cu2+ has been carried out by using running buffer of 60 mM acetate buffer and 2 mM cetyltrimethyl ammonium bromide (CTAB) at pH 4.0. The separation behaviors including interference of other metal ions, effect of buffer pH, buffer concentration, CTAB concentration have been examined. The method has been validated and applied to determine metal ions in serum sample.