Development of an electrochemical sensor composed of macaúba biochar for assessing caffeine levels

This study addresses the development of analytical methods to monitor caffeine concentration levels in stimulant beverages and capsules. For this purpose, an electrochemical sensor modified with macaúba biomass biochar was developed to evaluate caffeine by differential pulse voltammetry. The results indicate that the ideal proportions of the carbon paste components are 50 % graphite, 20 % macaúba biochar and 30 % binder. The voltametric analysis revealed a caffeine oxidation peak at 1.45 V, with linearity in the concentration range from 1.35 × 10^-5 mol·L^-1 to 1.03 × 10^-4 mol·L^-1. The calculated limits of detection (LOD) for soluble coffee, traditional cola-based soft drinks and central nervous system stimulant capsules were 3.52 μmol·L^-1, 0.65 μmol·L^-1 and 0.82 μmol·L^-1, respectively, and the limits of quantification (LOQ) were 11.7 μmol·L^-1, 2.15 μmol·L^-1 and 2.74 μmol·L^-1, respectively. Thus, this method is effective for evaluating caffeine, representing a promising alternative to traditional methods, being a low-cost method that proposes an environmentally friendly analysis.