The electrochemical detection of ascorbic acid (AA) was investigated using a cobalt(III)-ferritin immobilized on a self-assembled monolayer modified gold electrode in phosphate buffer solution (pH7.5). The modified electrode showed excellent electrochemical activity for oxidation of AA. The response to AA on the modified electrode was examined using cyclic and differential pulse voltammetry techniques. The resulting biosensor showed a linear response to AA in a concentration range from 6.25x10(-6) to 2.31x10(-5) M with sensitivity of 86,437 AM(-1) and detection limit of 4.65 x 10(-6) M based on a signal-to-noise ratio of 3. Electrochemical parameters including the charge transfer coefficient () and the apparent heterogeneous electron transfer rate constant (k(s)) for AA were found to be 0.52 and 1.054 Sec(-1), respectively. It has been shown that, using this modified electrode, AA can be determined with high sensitivity, low detection limit, and high selectivity. (C) 2015 International Union of Biochemistry and Molecular Biology, Inc.