Electrophoretically mediated micro-assay of alkaline phosphatase using electrochemical and spectrophotometric detection in capillary electrophoresis.

Electrophoretically mediated micro-assays of alkaline phosphatase (ALP) are demonstrated in capillary electrophoretic systems using both electrochemical (ED) and spectrophotometric (UV) detection. In the ED mode, p-aminophenylphosphate was used as the substrate and p-aminophenol (pAP) was monitored at a carbon fiber electrode held at +180 mV vs. Ag/AgCl. Spectrophotometric detection was achieved using the substrate p-nitrophenylphosphate, and monitoring the product p-nitrophenol (pNP) at 405 nm. The detection limit for pAP by ED was determined to be 100-fold lower than for pNP using UV detection. In the determination of ALP, both methods were found to be linear. The detection limit for ALP using zero potential assays with UV detection was determined to be 1.8.10(-6) mg/ml compared to 1.8.10(-7) mg/ml using ED.