Determination of Cinchona Alkaloids by Capillary Electrophoresis with Novel Complex Formation

The formation of a novel complex with cyclodextrin was investigated for the separation of cinchona alkaloids including the diastereomeric pairs of quinine, quinidine, cinchonine, and cinchonidine. The optimized separation of mixed cinchona alkaloids was obtained using 18 mM tris(hydroxymethyl)aminomethane, 3 mM Cu(II), and 20 mM hydroxypropyl-β-cyclodextrin at pH 5.7 with an applied voltage of 20 kV. Under these conditions, the four cinchona alkaloids were completely separated with resolution values between 9.08 and 3.94. The linear dynamic ranges for the analytes were from 10 to 1000 µg/mL with separation in less than 30 minutes. This method was used for the analysis of cinchona bark, quinine injection, and tonic water.