POLY(O-AMINOPHENOL)-MODIFIED BIENZYME CARBON-PASTE ELECTRODE FOR THE DETECTION OF URIC-ACID

A reagentless uric acid selective biosensor constructed by immobilisin g uricase and horseradish peroxidase (HRP) in carbon paste without the addition of an electron transfer mediator is described. The response of the electrode is based on the enzymatic reduction of hydrogen perox ide in the presence of uric acid. Uricase and HRP were dispersed in th e carbon paste and the optimum paste mixture was determined. Poly(o-am inophenol) was electropolymerised at the working surface area of the e lectrode acting as a conducting polymer layer. Cyclic voltametry was u sed to characterise the permselective characteristics of the polymer l ayer. At an applied potential of 50 mV vs. Ag/AgCl a linear response w as obtained up to 1 x 10(-4) M, with a limit of detection of 3 x 10(-6 ) M. The sensor had a response time of 37 s, a calibration precision o f 2.2%, (n = 4) and an estimated sample frequency of 20 h(-1). Respons es to the analyte of interest were pH dependent. The sensor was incorp orated into a flow injection system for the qualification of uric acid in human serum. Results compared favourably with a standard spectroph otometric method.