| The study of the high performance liquid chromatography-electrochemical detection (HPLC-ECD) and its related technologies which combine the high resolution of HPLC with the high sensitivity of ECD is an active research area in the analysis of complex multicomponent system. In this thesis, the methods detecting activated components in many kinds of food and medicine and evaluating the antioxidant ability of complex system have been established by HPLC-ECD and its related technologies; a palladium nanoarray electrode has been fabricated and the possibility of its application in the HPLC-ECD has been studied. The research holds very important significances in enriching the electrochemical technology and broadening the application range of HPLC and electroanalytical chemistry. The thesis consists of five chapters. The main contributions are summarized and presented as follows:1. The HPLC-ECD methods for determination of electroactive, weak electroactive or non-electroactive compounds in fifteen kinds of food and medicine have been established. The experimental results indicated that the sensitivity for electroactive compounds detected by ECD was 4-600 folds higher than those obtained by DAD, the detection limit can reach 2.2×103μg·mL-1. In addition, HPLC-ECD overcomes the disadvantage of HPLC-UV in being unable to conduct simultaneous and sensitive determination of compounds with different maximum UV absorption wavelengths. The weak electroactive compound apigenin and the non-electroactive compound chrysin were also detected sensitively by HPLC-ECD combined with online pre-column, the detection limits were 3.5×10-2 and 0.4μg·mL-1 respectively.2. The rapid, sensitive and accurate methods for the simultaneous separation and determination of four phenolic compounds, including protocatechuic acid, protocatechuic aldehyde, caffeic acid and ferulic acid, and tanshinone IIA in Fufangdanshen, Niaosaitong and Guanxintong tablets by high performance liquid chromatography using combined electrochemical detection with diode array detection (HPLC-ECD-DAD) have been established. The experimental results showed that the detection and quantification limits of four phenolic compounds with ECD were 7-28 folds lower than those obtained with DAD. As a non-electroactive compound, tanshinone IIA was detected with DAD sensitively. All calibration curves showed good linearity (r≥0.9992) within the test ranges. The recoveries ranged from 96.5% to 101.7%. Combining ECD with DAD can not only exert their respective advantages, but also widen its applications to detect various analytes in low level directly without the complicated process of enrichment, derivation and separated detection.3. By using the HPLC-ECD and HPLC-DAD-ECD-MS2 with offline pre-column reaction, a rapid, effective method for evaluating, screening and identifying antioxidants in complex system has been established. This method has been applied successfully to the identification of antioxidants in Buckwheat Honey and propolis. The experimental results indicated that this method not only serves as an ideal tool to monitor antioxidants but also provides their possible chemical structures.4. With field emission scanning electron microscope and energy dispersive spectroscopy, highly-ordered palladium nanoarray electrode has been fabricated by eletrodeposition in porous anodic aluminum oxide template. At the same time, the possibility of its application in HPLC-ECD has been studied. The experimental results showed that the palladium nanoarray electrode can be used as the working electrode of HPLC-ECD. It can be expected that the nanoarray electrode based on small dimension effects and surface effects can be applied in the analysis of micro amount, even the trace amount of compounds in the complicated system.
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