Capillary and microchip electrophoresis of basic drugs with contactless conductivity detection

The extension of contactless conductivity detection in electrophoresis to the determination of basic drugs is demonstrated using beta-adrenergic blocking agents (beta-blockers) and other physiologically active amines as examples. The high-voltage approach to conductivity detection was employed for conventional capillaries as well as microchip devices. Acidic buffers were used in all cases. A buffer consisting of 100 mm acetic acid and 1 mm histidine was deemed most optimal for the separation of six beta-blockers and best results for the analysis of the other amines were achieved with a 20 mm lactic acid buffer at low pH-value. The detection limits ranged from 0.06 to 5 mum. To demonstrate potential practical applications, a main component assay was conducted for three pharmaceutical formulations. On-chip, five pharmaceutical amines could be baseline-resolved in a 8 cm long microchannel in 90 s, albeit a reduced sensitivity and peak capacity compared to conventional capillary electrophoresis.