POLYBITHIOPHENE-MODIFIED ELECTRODE - SPECTROPHOTOMETRIC DETECTION OF ASCORBIC-ACID

A novel chemical detector for ascorbic acid using polybithiophene-modified indium tin-oxide glass electrode as sensing probe was developed. Reduction of polybithiophene occurred when doped polymer films were brought into contact with an aqueous solution of ascorbic acid; this redox reaction was accurately indicated by the change in chromatic property of the films. Therefore, the change in the UV-Vis absorption characteristics of the polymer was the measuring parameter for the detection of ascorbic acid. Experimental procedures for regenerating doped polybithiophene after each reduction by ascorbic acid are also described. Calibration curves were obtained from time-resolved spectrophotometric change of the doped polybithiophene films with respect to the concentration of ascorbic acid solutions. Based on the redox property of the conducting polymer, the working principle and stability of these modified electrodes are illustrated. Using packet fruit juice as test samples, the ascorbic acid level determined by the polybithiophene-based detector was comparable with that of the commercially available test kit.