Determination of dissociation constants of ten alkaloids by capillary zone electrophoresis

✍ Scribed by Suxuan Gong; Xiaodan Su; Tao Bo; Xu Zhang; Huwei Liu; Ke An Li

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 302 KB
• Volume: 26
• Category: Article
• ISSN: 1615-9306
• DOI: 10.1002/jssc.200390075

✦ Synopsis

Abstract

The dissociation constants of ten alkaloids, berbamine, (+)‐tetrandrine, thalifaretine, thalifaricine, northaltive, matrine, sophocarpine, sophoridine, oxymatrine, and oxysophocarpine isolated from herbal medicines Thalictrum and Sophora flavescens, were determined by capillary zone electrophoresis (CZE). The analysis time for each alkaloid was within 10 min under the following experimental conditions: acetate (pH 3.81–5.55) and phosphate buffer (pH 6.05–9.29) with ionic strength set at 0.03, applied voltage 30 kV, UV detection at 210 nm, capillary temperature 25°C. Effective mobility for each alkaloid and corresponding pH were fitted to an equilibrium expression by using nonlinear regression as well as linear regression, showing that the two models give comparable results for all studied alkaloids. The correlation coefficients were between 0.987 and 1.00 in the linear regression model, and between 0.978 and 1.00 in the nonlinear model. The measured p__K__~a~ values for the ten alkaloids were from 5.7 to 7.8. The p__K__~a~ values changed with the addition of organic additive to the buffer system.