Over-oxidized carbon paste electrode modified with pretreated carbon nanofiber for the simultaneous detection of epinephrine and uric acid in the presence of ascorbic acid

A new procedure for sensitizing of carbon paste electrode modified with carbon nanofiber by applying a special potential in differential pulse voltammetry is introduced. It is found out that the selection of 1.4 V as conditioning potential to a period of time can boost the electrochemical peaks of epinephrine and uric acid. In addition, the special potential leads to separated oxidation peaks of epinephrine and uric acid from ascorbic acid (potentially interfering species). The electrochemical impedance spectroscopic investigations confirm the good conductivity of the modified electrode. Surface characterization studies were done using scanning electron microscopy. Under optimum conditions, the oxidation peaks of epinephrine and uric acid were linear in the range of 0.1-150 mu M and 0.08-250 mu M, respectively, when they determined individually. The linear dynamic range from 0.2 to 30.0 mu M was obtained for the simultaneous determination of epinephrine and uric acid in the presence of ascorbic acid. Wide linear range, amplified and sharp peaks, reproducibility and stability allow this procedure to analyze epinephrine and uric acid in the presence of ascorbic acid. The proposed electrode was successfully applied for the determination of epinephrine and uric acid in epinephrine hydrochloride injection, human urine samples and human blood serum.