Electrode modified with manganese dioxide nanorods for the simultaneous voltammetric determination of food colorants

Synthetic colorants in particular tartrazine and brilliant blue FCF are widely used in food chemistry and technology although can give negative health effects of various severities. Moreover, brilliant blue FCF application is restricted in many countries. Therefore, sensitive and selective as well as simple and reliable methods for the quantification of these dyes are required. Voltammetric sensors suits well for such purposes. Glassy carbon electrode modified with manganese dioxide nanorods dispersed in cationic surfactant cetylpyridinium bromide gives a sensitive response to tartrazine and brilliant blue FCF in mixtures. Electrode modification provides 7.9-fold increase of the electroactive surface area as well as 72-fold decrease of electron transfer resistance i.e. improvement of the electron transfer rate. Simultaneous voltammetric quantification of colorants has been performed in phosphate buffer pH 7.0 in differential pulse mode. The linear dynamic ranges of 0.10-2.5 and 2.5-15 µM of tartrazine and 0.25-2.5 and 2.5-15 µM of brilliant blue FCF have been obtained with the limits of detection 43 and 41 nM, respectively. Dyes electrooxidation in the first linear range proceeds independently. The advantage of the sensor developed is the high selectivity of response in the presence of typical interferences (inorganic ions, saccharides, ascorbic and sorbic acids) and other food colorants (riboflavin, indigo carmine, sunset yellow). The practical applicability of the approach is shown on the soft and isotonic sports drinks and is validated by comparison to chromatography. Novel sensitive and selective voltammetric method is simple, express, reliable, cost-effective and can be applied for the beverages control.