Electrochemical interference study for determination of carminic acid in beverages

Abstract

The electrochemical behaviour of carminic acid in the environment of model lemonade, imitating the real composition of common soft drinks, was investigated at four types of commercially available screen-printed electrodes using cyclic voltammetry. The carminic acid displayed quasi-reversible waves in cyclic voltammograms which show the shift of the redox peak potentials to more negative values with increasing the pH. This phenomenon is caused by easier deprotonation of hydroxyl groups in an alkaline environment and their subsequent anodic oxidation to form the corresponding quinone counterpart with the participation of two electrons and two protons, which is typical for hydroxyanthraquinones. This study should lead in the development of a completely new screening electrochemical assay for field monitoring of total sum of carminic acid and carmine, commonly referred to as food additive E120.