| Capillary electrophoresis (CE) is an important and powerful technique in the area of liquid-phase separations. The separation principle is based on the phenomena that ionized molecules of different mass or/and charge will travel with different velocities through a fused silica capillary under the force of a high-voltage electric field. Due to the different velocities, the analytes can be separated and then detected by the detector. Thanks to its high separation efficiency, short analysis time, low cost, environmental friendliness and small sample consumption, CE has been widely flourishing in many areas such as food analysis, pharmaceutical analysis, biochemical analysis, and environmental analysis etc. Since Electrochemical detection (ED), especially amperometric detection (AD) has many advantages over other widely used techniques in that it is much more economical, without complicated pretreatment procedure, and it provides good selectivity as well as high sensitivity, so it has flourished to various areas. From the standpoint of broadening its application areas and enhancing the detection sensitivity, we mainly focus on the development of new chemically modified electrode (CME), the application of additive in CE and new method of CE-AD.This paper, composed of four chapters, begins with a brief introduction of CE, its separation principle and separation models, the detection methodologies, its application areas, as well as the meanings of this paper.Chapter two developed an effective CZE-AD method with the addition of beta-cyclodextrin (β-CD) in the running buffer and addtion of ethanol in injected sample solution to separate and detect flavonoids and phenolic acid in Chinese herbal tea. The effects of working electrode potential, pH and concentration of running buffer, concentration ofβ-CD, separation voltage and injection time were investigated. The six analytes could be separated within 20 minutes with the detection limits as low as 10-8 g ml/L-1(S/N=3). The method was applied to analyze tea samples with recoveries in the range of 90.0-107.0%. The method offers high separation efficiency, short analysis time, small sample consumption, and good repeatability.Chapter three is mainly about the separation and simultaneous determination of three isomers of phenylenediamines (o-, m-p-phenylenediamine) and two isomers of dihydroxybenzenes (catechol and resorcinol) in hair dyes by capillary zone eletrophoresis coupled with amperometric detection (CZE-AD) with the help of platinum working electrode. In order to search for the optimum experimental conditions, the effects of working electrode potential, pH and concentration of running buffer, separation voltage and injection time on CZE-AD were investigated. Under the best experimental conditions, the five analytes could be separated within 15 minutes, with linear ranges from 1.0×10-6 to 1.0×10-4 molL-1. The detection limits were as low as 10-7 molL-1 magnitude (S/N=3). This method was successfully used to analyse eight kinds of hair dyes samples with recoveries in the range 91.0-108.0%. The experimental results showed that capillary zone electrophoresis coupled with amperometric detection using platinum working electrode was of high sensitivity and good repeatability, and this method could be applied in the rapid determination of practical samples.In Chapter four, a new kind of vitamin B12 (acquo-cobalamine) chemically modified electrode was developed and employed in capillary zone electrophoresis coupled with amperometric detection (CZE-AD) for simultaneous determination of some antioxidants (including glutathione, ascorbic acid, vanillic acid, chlorogenic acid, salicylic acid, and caffeic acid) in fruits and vegetables. Compared with common carbon disk electrode, the catalytic electrochemical properties of the chemically modified electrode could obviously enhance oxidation peak currents responses by about five times. Furthermore, the effects of working electrode potential, pH and concentration of running buffer, separation voltage and injection time on CZE-AD were investigated. Under the optimum conditions, the six analytes could be completely separated and detected in a borate-phosphate buffer (pH 8.4) within 15 min. Their linear ranges were from 2.5×10-7 to 1.0×10-4 molL-1 and the detection limits were as low as 10-8 molL-1 magnitude (S/N=3). The proposed method had been successfully employed in the analysis of practical samples with recoveries in the range 96.0-106.0%. Above results demonstrated that CZE-AD using vitamin B12 modified electrode was of good stability, high sensitivity, good repeatability, and could be used to analyze the practical samples.
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