Further voltammetric studies of synthetic food colouring matters at glassy carbon and carbon paste electrodes using static and flowing systems

Abstract

Linear-sweep anodic peaks of synthetic food colouring matters at a stationary carbon paste electrode have been found to be generally sharper, to be better resolved from the cut-off current and to have a lower base-line current than those obtained at a glassy carbon electrode. All of the food colours studied also gave cathodic peaks at a stationary glassy carbon electrode but there was fluctuation of peak potential and instability of peak shape with some colours. The cathodic peak potentials of the yellow food colours were particularly well separated. The more limited negative potential range available with carbon paste restricted study to ten food colours.

The voltammetric waves of four food colours showed some reversibility when studied by cyclic voltammetry. The anodic peaks of the triphenyl-methane colours, Green S, Patent Blue V and Brilliant Blue FCF, show small peaks on the reverse scan. Indigo carmine is unique in having a large peak on the reverse scan of the cathodic peak.

Carbon paste and glassy carbon electrodes used anodically in the wall-jet configuration have been shown to give good precision, rectilinear calibration graphs and low limits of detection for the determination of food colours by flow-injection analysis.