Amperometric determination of ascorbic acid based on electrocatalytic oxidation using a ruthenium(III) diphenyldithiocarbamate-modified carbon paste electrode

A modified carbon paste electrode was prepared with an aqueous insoluble redox mediator, ruthenium(III) diphenyldithiocarbamate. The electrode was scanned between 0.0 V to +0.8 V in KNO3 medium. The modified electrode electrocatalytically oxidises ascorbic acid. Conditions such as pH and scan rate have been optimised for the determination of ascorbic acid. A linear response was observed in the range of 2.5-125 mg l(-1), with a correlation coefficient (r), of 0.9998. Standard deviation for 10 repetitive determinations was found to be 100 +/- 0.6. The stability and reproducibility of the electrode for determinations were also discussed. Hydrodynamic voltammogram was also recorded for electrocatalytic oxidation. Amperometric determination and studies on the stability of the electrode were carried out for a period of 10 days. (C)2000 Elsevier Science B.V. All rights reserved.