Simultaneous voltammetric method for quality control of brilliant blue FCF and tartrazine in beverages

Brilliant Blue FCF (BB; INS 133) and tartrazine (TZ; INS 102) are among the most used synthetic dyes in processed foods and beverages, enhancing product appearance and consumer acceptance. However, the widespread use of these additives requires effective analytical strategies to ensure compliance with food regulations and product safety. In this work, a voltammetric method was developed for the simultaneous determination of BB and TZ using a boron-doped diamond electrode (BDDE). Voltammetric measurements were performed using an Autolab PGSTAT 101 potentiostat/galvanostat connected to an electrochemical cell containing the BDDE as the working electrode, an Ag/AgCl (3.0 mol L^-1 KCl) as reference electrode, and a platinum plate as the auxiliary electrode. Both dyes presented well-defined oxidation peaks at 0.95 V and 1.20 V, respectively, for BB and TZ, in Britton–Robinson (BR) buffer solution (pH 2.0), employing cyclic voltammetry and the cathodically pretreated BDDE (−0.25 A cm^-2, 240 s). The peak potential separation of approximately 250 mV demonstrates the suitability of the proposed method for the simultaneous analysis of both dyes. The analytical curve was constructed using square-wave voltammetry (frequency: 30 Hz, amplitude: 0.1 V, potential increment: 2 mV) by varying the dyes concentration and obtaining linearity in the range from 0.69 to 6.25 µmol L^-1 for BB and from 0.49 to 4.46 µmol L^-1 for TZ, with limit of detection of 4,20 nmol L^-1 and 3,60 nmol L^-1, respectively. The method was successfully applied to the determination of BB and TZ in beverage samples (isotonic drinks and soft drinks). The results demonstrate that the cathodically pretreated BDDE in conjunction of voltammetry provides a simple, sensitive, and reliable platform for the simultaneous determination of BB and TZ, showing potential for application in quality control of beverages.