Analytical performance of poly(L-cysteine) modified pencil graphite electrode for dapsone detection

The electrochemical analysis of dapsone (DP) was carried out using a poly-L-cysteine (poly-L-Cys) modified pencil graphite electrode (poly-L-Cys/PGE) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The method was optimised by examining the experimental parameters, including how the scan rate, DP concentration, and pH affected the current response. The electrochemical behavior of DP at the modified electrode showed that the process mainly relies on adsorption. Under these optimised conditions, the anodic peak current from DPV measurements showed a linear relationship with DP concentrations between 1.0 × 10^-6 and 12.0 × 10^-6 M, yielding a detection limit (LOD) of 5.37 × 10^-7 M. The method showed great sensitivity, selectivity, and stability. To test its practical use, the technique was successfully applied for the quantitative determination of DP in commercial tablet formulations and urine samples. Additionally, examination of the effects of common interfering substances confirmed minimal interference with DP detection. This electroanalytical approach offers a reliable, cost-effective alternative for routine DP determination in clinical laboratories, pharmaceutical analysis, and quality control.