Determination of Anisodamine Enantiomers in Rabbit Plasma Samples by Solid-phase Extraction with Capillary Electrophoresis

To establish a capillary electrophoresis method under which anisodamine enantiomers can be sufficiently separated for quantification, hydroxypropyl-beta-cyclodextrin (HP-beta-CD), methyl-beta-cyclodextrin (Me-beta-CD) and carboxymethyl-beta-cyclodextrin (CM-beta-CD) were used as chiral selectors. Effects of the concentration of cyclodextrin, pH and concentration of buffer were investigated. The baseline separation of four enantiomers of anisodamine was obtained in 110 mmol/L Tris-H3PO4 buffer-20.0 mg/mL HP-beta-CD-5.0 mg/mL CM-beta-CD at pH 4.0. Prior to electrophoresis, the analytes were purified and preconcentrated by solid phase extraction from plasma. Standard curves constructed using blank plasma spiked with anisodamine in the range 77.86 similar to 0.39 mu g/mL, showed acceptable linearity with correlation coefficients, r >= 0.999. The detection limits for the four enantiomers of anisodamine were all 0.08 mu g/mL. Mean intra- and inter-day precisions (RSD%) were <4.2% and 6.5%, respectively. The method showed recoveries for the four enantiomers ranging from 95.1% to 105%. Acceptable precision and accuracy of the method were demonstrated for pharmacokinefic studies by determining the concentrations of anisodamine enantiomers in rabbit plasma, after administration of 75 mg of anisodamine during three consecutive days.