The use of apple-modified carbon paste electrode for the determination of dopamine by differential pulse voltammetry is demonstrated. The polyphenol oxidase present in apple tissue can selectively recognize and catalyze the oxidation of dopamine to quinone dopamine. The electrochemical reduction of the generated quinone dopamine can be used for the determination of dopamine. The linear dynamic range of this biosensor is between 0.40 and 25.2 M of dopamine concentration by differential pulse voltammetry method. The limit of detection is 0.2 M at 298 K. The relative standard deviation for the determination of dopamine is 2% at a concentration of 10.0 M. The biosensor is stable for nearly two weeks. No significant interference was noted from some potentially interfering compounds. Finally, the accuracy of method is tested by recovery experiments in synthetic samples and the suitability of the method was tested by determination of dopamine in dopamine hydrochloride injections.
