Electrochemical oxidation of L‐ascorbic acid at the graphite electrode and its monitoring by a thick‐film graphite sensor assembly

The experimental results obtained in this study show that a thick‐film graphite sensor assembly (with a Pt counter and an Ag/AgCl reference electrode) can be conveniently fabricated by the photolithographic and screen‐print metallization techniques. This sensor has been successfully employed for quantitatively determining L‐ascorbic acid concentration in aqueous solutions with reasonably good reproducibility. This sensor provides the possibility of developing a miniature size practical device for detecting ascorbic acid in biochemical processing, such as in food and drug production. The mechanistic aspects of the oxidation of L‐ascorbic acid on optical pyrolytic graphite electrodes were further studied with a rotating OPG disk electrode in two different electrolyte solutions. It was found that the oxidation of L‐ascorbic acid is more favored in pH = 7 solutions than in pH = 1 solutions although a common 2‐electron transfer pathway is applied in both cases.