Designing Of Apparatus Of Capillary Electrophoresis With Amperometric Detection And Its Application

Tryptophan (Trp) and its main metabolites (3-hydroxy-Dl-kynurenine, 5-hydroxy-l-tryptophan, Dl-kynurenine, 5-hydroxyindole-3-acetic acid, Xanthurenic acid, Indole-3-pyruvic acid, 5-hydroxytryptamine, Tryptamine) (be comprehensively termed as Trps) play important roles in the physiological processes in human bodies. Studies on them not only can help people learn to diagnose and treat many kinds of diseases, but also can provide ideas to investigate the mechanism of some psychic diseases. Traditionally, high performance liquid chromatography (HPLC) is employed to study the metabolic process of Trp and the characteristics of Trps. As a newly arisen separation analytical technique, capillary electrophoresis (CE) has some distinctive advantages, which makes it be very suitable for separation of these kinds of compounds. But only a few reports were related to its applications in the study of metabolic process. Owe to Trps' electroactivity, capillary electrophoresis with amperometric detection(CE-AD)was employed to separate and detect Trps simultaneously as well as to study the metabolic process of Trp in this thesis, which was of benefit to the application of CE in the study of metabolic process of medicines. This thesis includes four parts. The first part is the review of the development of CE, in which CE-AD is introduced especially. The metabolic process of Trp and analytical methods for Trps are also presented in this part.In the second part, a laboratory-built CE-AD apparatus was introduced in detail. In this apparatus, four new designed systems (self-aimed electrolytic cell system, water-cooling system, high-voltage power supply system and sampling system) were equipped. The test of the apparatus showed that it was competent for separationcomplex compounds.In the third part, a high performance method has been developed for separation and determination of Trps by micellar electrokinetic capillary chromatography (MECC). At 24 kV applied voltage, the nine compounds were completely separated within 23min in 10mol/LNa2HPO4-10mol/LNaOH buffer (pH=11.0) including 40mmol/L SDS and 3%(vol.) methanol. This method has been successfully applied to analyze the metabolic process of Trp in rabbit urine. Kynurenine was also successfully detected in some urine samples.In the fourth part, the glassy carbon electrode was modified electrochemically by pretreatment in sodium hydroxide solution by means of Cyclic Voltammetry (CV). The electrochemical oxidation of Xanthurenic acid (XA) has been studied in aqueous solutions at modified glass carbon electrode (MGCE). The oxidation process has been shown to be irreversible and diffusion-controlled. A voltammetric method was developed for the quantitative determination of XA in 0.2mol/LH3PO4- 0.05mol/L Na2B4O7 (pH＝2.0) buffer at MGCE. The peak current showed a linear relationship with concentration in the range of 3.0×10-7～1.0×10-5mol/L by Differential Pulse Voltammetry (DPV). This method has been successfully applied to determine XA in urine sample by standard addition, and the recovery is 103.4%...