Rice Husk Biochar: A Promising Material for the Development of Electrochemical Devices for Tartrazine Determination

This study presents the successful application of rice husk biochar (BC) in modifying carbon paste electrodes for the voltammetric determination of tartrazine (Tz) in commercially available juices. The BC was produced under different pyrolysis conditions using a central composite rotational design, in which the evaluated parameters were heating rate, biomass amount, temperature, and time. All BC samples obtained were used to modify the carbon paste electrode, and the best pyrolysis conditions (400 °C, 20 g of rice husk, a heating rate of 25 °C min^-1, and a pyrolysis time of 180 min) were determined based on the highest Tz current response obtained by differential pulse voltammetry. The obtained material was characterized by thermogravimetry, N₂ adsorption/desorption isotherms, scanning electron microscopy, Fourier transform infrared spectroscopy, and electrochemical impedance spectroscopy. The electrode composition was also evaluated, and the highest current response Tz was obtained in the electrode containing 70% graphite, 22.5% liquid paraffin, and 7.5% BC. The influence of experimental parameters was then evaluated for this electrode, and the best conditions were obtained in 0.1 mol L^-1 phosphate buffer solution (pH = 2), E _step of 0.008 V, and amplitude of 0.12 V. The Tz analytical curve was linear from 50 to 350 mg L^-1, and the detection and quantification limits calculated were 0.17 and 1.57 mg L^-1, respectively. To evaluate accuracy, recovery tests were used, yielding values between 84 and 117%. The method was successfully applied to six samples of two juice brands in the market, demonstrating its practicality and reliability. These results highlight the potential of BC-based electrodes as sustainable and effective alternatives for food analysis.