Determination of levodopa by capillary zone electrophoresis using an acidic phosphate buffer and its application in the analysis of beans

A simple capillary zone electrophoresis method has been developed for the quantification of levodopa in broad bean and lentil. The dependence of effective mobility of levodopa on pH was investigated in the range of 1.64-11.20; and the simulated apparent dissociation constant values of levodopa were 2.30, 8.11 and 9.92, respectively, which were consistent with literature values. Meanwhile, we obtained the isoelectric point for levodopa was 5.20. Levodopa could be well separated from sample matrix and determined with conditions of 35 mM NaH2PO4, pH 4.55, 17.5 kV and 30 °C. A plot of the peak area on levodopa concentration was linear over the range of 5.0-300 μg/mL with a correlation coefficient of 0.9994. The method was validated for the quantification of levodopa in beans. The recoveries of added levodopa in different samples were 99.8% and 105.0%, respectively.