A simple method to determine Allura Red (AR) in cherry gelatin, chili sauce and strawberry juice by square-wave adsorptive stripping voltammetry (SWAdV) in the presence of cetylpyridinium bromide (CPB) is reported. Using a glassy carbon electrode (GCE), Amaranth (AM), Ponceau 4R (P-4R) and AR were oxidized to very close potential values in medium acid pH 3.0 with phosphate buffer solution (PBS), making selective AR detection impossible. Under these conditions AM, P-4R and AR were oxidized at 0.80, 0.77 and 0.81 V, respectively. When small amounts of CPB were added, an AR-CPB aggregate was formed. This change displaced the oxidation almost 0.14 V in the direction of the most positive potential and increased the current almost 50%, while AM and P-4R were oxidized at almost the same potential. Under these conditions, the selective determination of AR in food was possible. Detection limit was 0.032 μmol L-1. Finally, the method was successfully applied to the determination of AR in these foods.
Keywords: Allura Red; Amaranth; Ponceau 4R; cetylpyridinium bromide; glassy carbon electrode.