Amperometric detection of three purine alkaloids following their separation by micellar electrokinetic capillary chromatography

Abstract

The separation and determination of three alkaloids by micellar electrokinetic capillary chromatography (MECC) with amperometric detection (AD) was reported. A carbon disk electrode used as working electrode for the alkaloids exhibit good responses at +1175 mV (versus Ag/AgCl). On a 70 cm length, 25 μm i.d. capillary, baseline separation is possible with a carrier solution containing 35 mmol/l sodium dodecyl sulphate (SDS) in 20 mmol/l, pH 8.5 phosphate buffer solution. The migration time and peak current of solutes increased markedly and decreased with increasing SDS concentration. Under the optimized conditions, the separation of three purine alkaloids was accomplished within 13 min. The determination of them was performed by using good linearity between peak current and concentration for all three analytes with correlation coefficients from 0.9979 to 0.9993 and recoveries from 95.34 to 104.91%. The method was applied successfully to determine the active ingredients of the composite theophylline tablets and the assay results was satisfactory.