Studies Base On The Efficient Separation And High Sensitivity Detection Of Capillary Electrophoresis

Capillary electrophoresis(CE), based on the separation of charged molecules through a small capillary under the influence of an electric field, has emerged as a powerful analytical separation technique for the determination of numerous analytes from organic molecules to macromolecules with attractive features, such as high resolving power and small sample volume. Nowadays, it is utilized for the daily assays as an excellent complement to high-performance liquid chromatography. The aim of the thesis is to establish the efficient, sensitive capillary electrophoresis methods and apply to the separation of flavonoids and ascorbic acid in real samples. The thesis is composed of four parts.In the first part, the history of capillary electrophoresis technology was reviewed,and the fundamental theory, basic separation models, characteristics and detectors of CE were introduced. At the same time, we narrated the present development hotspots of CE in detail, as well as the goal and significance of this paper.In the second part, a laboratory-built capillary electrophoresis with electrochemical detection was developed for the simultaneous determination of three flavonoids (naringenin, rutin, quercetin) and ascorbic acid. To obtain the best separation efficiency, the experimental parameters such as buffer type, concentration, pH, detection potential, separation voltage, etc. were carried out a detailed investigation. It was found that naringenin, rutin, quercetin and ascorbic acid were well separated within 5 min in borate buffer solution (pH 8.6, 24 mM). The detection limit was 1.0μM for naringenin, 8.0μM for rutin, 2.0μM for ascorbic acid and 0.5μM for quercetin. The protocol was successfully applied for the determination of the analytes in rat serum and excrement. Recovery results ranged from 90.9% to 108.6%.In the third part, the study for the separation of three flavonoids (naringenin, rutin and quercetin) and ascorbic acid by modified capillary electrophoresis (CE) with UV detection was described. The capillary modified by polyelectrolytes and silica nanoparticles (SiNPs) using dynamic coating or layer-by-layer technique was used to increase the resolution and sensitivity of the separation and determination. The modification of (diallyldimethylammonium chloride) (PDDA) -silica nanoparticles- poly (styrenesulfonate) (PSS) was the most effective capillary. The four analytes could be well separated using a separation voltage of 18 kV in 24 mmol/L borate buffer solution (pH 8.3). The theoretical plate numbers obtained were all above 6.5×103 theoretical plates per meter, which were improved obviously compared with the native capillaries. The proposed method was successfully applied for the rapid CE determination of trace naringenin, rutin, quercetin and ascorbic acid in human urine with satisfied results.In the fourth part, the connection of capillary electrophoresis with Electrochemiluminescence was preliminary studied. A novelμ-ECL cell based on flow injection which can well couple with CE technology was designed and fabricated. The key factors such as the effect of high voltage on luminescence detection were studied. The cell had solved these probloms well and provided hardware for further study. It will have a wide application in the real research and analysis.