Voltammetric determination of food colorants using a polyallylamine modified tubular electrode in a multicommutated flow system

This work describes the construction of a polyallylamine modified tubular glassy carbon electrode and its application in the electroreduction of food azo colorants (tartrazine, sunset yellow and allura red) by square wave voltammetry. The electrode modification prevented the surface fouling and, simultaneously, enhanced the analytical signal intensity. The developed unit was coupled to a multicommutated flow system which, given the complexity of samples, was designed to allow the implementation of the standard additions method in an automatic way, using only one standard solution. The described method presented a linear range up to about 2.0 × 10 −4 mol l −1 for the referred colorants, with a detection limit of 1.8 × 10 −6 mol l −1 for tartrazine, 3.5 × 10 −6 mol l −1 for sunset yellow and 1.4 × 10 −6 mol l −1 for allura red. The method was applied in the analysis of these colorants in several food samples, and no statistically significant difference between the results obtained by the proposed and the comparative method (HPLC) was found, at a 95% confidence level. Repeatability in the analysis of samples (expressed in R.S.D.) was about 3% ( n = 10).