Simple and Efficient Epinephrine Sensor Based on Carbon Nanotube Modified Carbon Film Electrodes

A simple electrochemical sensor for epinephrine (EP) has been developed by modification of a carbon film electrode (CFE) with multiwalled carbon nanotubes (MWCNTs) in a chitosan matrix. Cyclic voltammetry (CV) was employed for the evaluation of the electrochemical oxidation of EP at modified electrodes MWCNT/CFE in different pH electrolytes. Under the optimum conditions (pH 7.0), the MWCNT/CFE electrode showed significant electrocatalytic oxidation of EP: a decrease of about 200 mV in the overpotential and an 11-fold increase in the peak current, compared with the unmodified CFE. Detection of EP was carried out by CV, fixed potential amperometry, and differential pulse voltammetry (DPV); the most sensitive response with the lowest detection limit of 0.9 µM obtained by DPV with preconcentration. At MWCNT/CFE, a separation of 175 mV between EP and ascorbic acid peaks was found. The sensor exhibited excellent stability over a period of 6 months and was successfully applied to the analysis of injectable adrenaline solutions.