Application Study Of Capillary Electrophoresis With Electrochemical Detection In Analysis Of Foods And Tarditional Chinese Medicines

The history, the current situation and the future trend of capillary electrophoresis (CE) is reviewed. CE is becoming increasingly recognized as an important analytical separation technique due to its speed, efficiency, reproducibility, ultra-small sample volume, and ease of clearing up the contaminants. CE has been widely applied in many fields. In combination with electrochemical detection (ED), CE-ED offers high sensitivity and good selectivity for electroactive species. The present dissertation described the studies of CE-ED application in the analyses of foods and traditional Chinese medicines. The major content is described as follows:1. Determination of phenolic constituents of biological interest in red wine by capillary electrophoresis with electrochemical detectionA simultaneous determination of /ram-resveratrol, (-)-epicatechin and (+)-catechin in red wine by capillary electrophoresis with electrochemical detection (CE-ED) was reported. The effects of potential of working electrode, pH and concentration of running buffer, separation voltage and injection time on CE-ED were investigated. Under the optimum conditions, the analytes could be separated in a 100 mmol/L borate buffer (pH=9.2) within 20 min. A 300 um diameter carbon disk electrode has a good response at +0.85 V (vs.SCE) for all analytes. The response was linear over three orders of magnitude with detection limit (S/N=3) ranged from 2 X 10'7 g/mL to 5 X 10"7 g/mL for all analytes. This method has been used for the determination of these analytes in red wine without enrichment, and the assay result was satisfactory.2. Determination of isoflavones in soy products by capillary electrophoresis with electrochemical detectionSimultaneous determination of daidzein and genistein in soy products by capillary electrophoresis with electrochemical detection (CE-ED) was reported. The effects of working electrode potential, running buffer pH, separation voltage and injection time on CE-ED were investigated. Under the optimum conditions, the analytes could beseparated in a 100 mmol/1 borate buffer (pH=11.0) within 20 min. A 300 urn diameter carbon disk electrode has a good response at +0.70 V (vs. SCE) for the analytes. The response was linear over three orders of magnitude for the analytes. This method has been satisfactorily used for the determination of daidzein and genistein in several actual soy samples.3. Determination of polyphenols in apple juices and ciders by capillary electrophoresis with electrochemical detectionA simultaneous determination of phloridzin, (-)-epicatechin, chlorogenic acid and myricetin in apple juices and ciders by capillary electrophoresis with electrochemical detection (CE-ED) was reported. The effects of potential of working electrode, pH and concentration of running buffer, separation voltage and injection time on CE-ED were investigated. Under the optimum conditions, the analytes could be separated in a 50 mmol/L borate buffer (pH=8.7) within 20 min. A 300 um diameter carbon disk electrode has a good response at +0.90 V (v.y. SCE) for all analytes .The response was linear over three orders of magnitude with detection limit (S/N=3) ranged from 1 X 10-8 g/mL to 5X10-7 g/mL for all analytes. This method has been used for the determination of these analytes in apple juices and ciders, and the assay result was satisfactory.4. Determination of phenolic compounds of buchwheat (Fagopyrum esculentum Moench) hulls and flour by capillary electrophoresis with electrochemical detectionA simple, reliable and reproducible method, based on capillary electrophoresis with electrochemical detection (CE-ED), for the determination of phenolic compounds of buckwheat (Fagopyrum esculentum Moench) hulls and flour was reported. The active ingredients mainly consist of (-)-epicatechin, rutin, hyperoside and quercetin. Operated in a wall-jet configuration, a 300 um diameter carbon disk electrode was used as the working electrode, which exhibits good response at +0.90 V (v.v. SCE) for all analytes. The effects of poten...