Electrochemical Behavior and Sensitive Methods of the Voltammetric Determination of Food Azo Dyes Amaranth and Allura Red AC on Amalgam Electrodes

Abstract

The novel and highly sensitive methods for individual determination of two food azo dyes Amaranth (AM, E 123) and Allura Red AC (AR, E 129) in the commercial beverages were successfully developed on two types of silver solid amalgam electrodes, namely mercury meniscus modified (m-AgSAE) and liquid mercury free polished (p-AgSAE) amalgam electrodes, using differential pulse adsorptive stripping voltammetry (DP-AdSV) and direct current adsorptive stripping voltammetry (DC-AdSV) for the first time. In addition, the reduction processes of AM and AR on amalgam electrodes were compared with the processes on hanging mercury drop electrode. The influence of pH, accumulation potential, and accumulation time on the signal enhancement of AM and AR were investigated. The number of electrons and the number of protons participating in the rate-determining step of the reduction process for azo dyes were calculated. Due to the significantly increasing reduction peak currents of AM and AR on m-AgSAE and p-AgSAE caused by their adsorption at the electrode surface, the amalgam electrodes exhibit the wide linear ranges and good sensitivity to the determination of AM and AR. For example, the limits of detection were found to be 2.1 × 10−9 mol L−1 for AM and 3.4 × 10−9 mol L−1 for AR on m-AgSAE using DC-AdSV. Moreover, the amalgam electrodes showed good repeatability (RSD lower than 5.0% for 5 × 10−8 mol L−1 of tested azo dyes) and stability and it was confirmed that these electrodes are useful tools to azo dye monitoring in a food safety control field.