Simultaneous analysis of polyhydroxylated alkaloids by capillary electrophoresis using borate complexation and evaluation of sweeping technique for sensitivity improvement

Capillary zone electrophoresis coupled to UV detection was used for the simultaneous analysis of naturally occurring polyhydroxylated alkaloids. This separation was based on an in-situ complexation with borate ions. The effect of parameters such as borate concentration, capillary temperature and analyte molecular structure on migration times and selectivity were discussed. The best separation was obtained with a fused silica capillary (48.5 cm total length x 50 mum I.D., with a bubble factor of 3), 80 mM sodium tetraborate aqueous solution at pH 9.2 and temperature of 20degreesC. The method was validated and showed good data in terms of migration time and peak area reproducibility, selectivity, linearity and accuracy. The validated method was applied to determine miglitol in commercially available pharmaceutical tablets. To further improve method sensitivity, a sweeping technique involving borate ions was evaluated. This technique was found very sensitive to the analyte complexation with borate, borate concentration, and temperature as well as sample matrix. In the case of miglitol, a 35-fold improvement in peak height was achieved.