Selective voltammetric detection of epinephrine in the presence of ascorbic acid at poly(4-methoxyphenol)-modified electrode

A gold electrode was modified with electropolymerized films of 4-methoxyphenol by its oxidative polymerization from an alkaline solution by cyclic voltammetry. The modified electrode was then used to determine epinephrine (EP) in the presence of a high concentration of ascorbic acid (AA) by differential pulse voltammetry. The peak positions as well as relative sensitivity EP/AA were affected by the potential window used for the polymerization. For polymerization between 0 and 1.3 V, the peak potentials recorded in a phosphate buffer solution (pH = 7.2) were 516 and 312 mV vs. Ag/AgCl for EP and AA, respectively. In addition the effects of pH and the type of electrolyte on the linearity range and detection limit are investigated. The detection limit for 3s-test is 0.1 muM. The high selectivity and sensitivity for epinephrine was found to be due to charge discrimination/analyte accumulation.