Studying current-potential curves throughout a bipotentiometric iodometric back-titration for the determination of ascorbic acid in fruits and vegetables

VERDINI, RA; LAGIER, CM

JOURNAL OF CHEMICAL EDUCATION

American Chemical Society

Año: 2004 vol. 81 p. 1482 - 1485

0021-9584

A method for the determination of ascorbic acid content in vegetables and fruits was used to introduce the principles of voltammetry. The procedure combines an iodometric back-titration with voltammetric (bipotentiometric) end-point detection, which minimizes the risk of ascorbic acid oxidation, allowing for a rapid and efficient quantification of vitamin C in vegetable and fruit samples. A better understanding of the titration curve is achieved by analyzing the schematic current-potential curves of the anodic and cathodic half-cell reactions during the titration. Hence, not only theoretical principles of voltammetry are considered, but also the applications of these techniques to quantify a chemical specie in a complex matrix. As a result, the laboratory practice proposed is a valuable tool for analytical chemistry students to discuss electrochemistry techniques, in the context of an interesting application, when attending instrumental analysis courses.