Qingcui Chu

Separation of six purine bases by capillary electrophoresis with electrochemical detection

Abstract Capillary zone electrophoresis with electrochemical detection (ED) has been employed for the separation and determination of adenine (A), guanine (G), theophylline (Thp), hypoxanthine (HX), xanthine (Xan) and uric acid (UA). Effects of several important factors such as the acidity and concentration of running buffer, separation voltage, injection time and detection potential were investigated to acquire the optimum conditions. The detection electrode was a 300xa0μm carbon disc electrode at a working potential of +0.95xa0V (versus saturated calomel electrode (SCE)). The six purine bases can be well separated within 14xa0min in a 40xa0cm length fused-silica capillary at a separation voltage of 10xa0kV in a 100xa0mmol/l borate buffer (BB, pH 10.0). The current response was linear over about three orders of magnitude with detection limits (S/N=3) ranging from 0.157×10 −6 to 0.767×10 −6 xa0mol/l for all compounds. The proposed method was successfully applied to determine Thp in tea and aminophylline tablets, UA in human urine, and two purine bases in DNA.

Determination of puerarin and daidzein in Puerariae radix and its medicinal preparations by micellar electrokinetic capillary chromatography with electrochemical detection

Abstract The use of micellar electrokinetic capillary chromatography (MECC) with electrochemical detection is described for the determination of puerarin and daidzein in Puerariae radix and its medicinal preparations. Operated in a wall-jet configuration, a 300xa0μm diameter carbon-disk electrode was used as the working electrode, which exhibits good responses at +900xa0mV (versus SCE) for the two analytes. Under the optimum conditions, the analytes were base-line separated within 11xa0min in a sodium dodecyl sulphate—borax (pH 7.8) running buffer, and excellent linearity was obtained in the concentration range from 5.0×10 −4 to 5.0×10 −6 xa0mol/l. The detection limit (S/N=3) was 6×10 −7 and 1.1×10 −6 xa0mol/l for puerarin and daidzein, respectively. This work provides a useful method for the analysis of traditional Chinese medicines.

Determination of phenols in Fructus Lycii by capillary electrophoresis with electrochemical detection

A high-performance capillary electrophoresis with electrochemical detection (CE-ED) method has been developed for the determination of bioactive phenols in Fructus Lycii samples. Under the optimum conditions, the seven analytes could be well separated within 24 min in a 80 mM borax running buffer. Good linear relationship was established between peak current and concentration of analytes over three orders of magnitude with detection limits (S/N = 3) ranging from 3.5 × 10−8 to 6.0 × 10−8 g/mL for all analytes. The proposed method has been successfully applied for the study on the efficiency of electrochemically active ingredients in polar extracts of Fructus Lycii after a relatively simple pretreatment.

Study on electrochemical profiles of Valeriana medicinal plants by capillary electrophoresis

The objective of this work was to develop a high-performance capillary electrophoresis with amperometric detection (CE-AD) method for the determination of pharmacologically active ingredients in extracts of Valeriana medicinal plants. The method was validated for linearity, repeatability, limits of detection (LODs) and limits of quantification (LOQs), etc. The LODs and LOQs of eight compounds were found to be in the range from 1.0 × 10−8 to 1.2 × 10−7 and 3.3 × 10−8 to 4.0 × 10−7 g/mL, respectively. The proposed method was successfully applied for the analyses and comparison of bioactive components in Valeriana samples after a relatively simple extraction procedure, and the resultant “electrochemical profiles” can intuitively demonstrate the content diversity of each electrochemically active ingredient in Valeriana samples from different places and plant parts. It was found the content of bioactive ingredients may vary by an order of magnitude depending on natural conditions, e.g. soil, climate, humidity etc.