Biochar for Electrochemical Sulfanilamide Detection: Comparative Evaluation of Carbon Paste and Screen-Printed Electrodes

Antibiotics such as sulfanilamide (SFD) pose significant environmental and health risks due to their persistence in wastewater and their potential to contaminate food. However, conventional detection methods for these compounds are often costly and time-consuming. This study proposes activated biochar derived from sugar cane bagasse as a sustainable modifier for electrochemical sensors to detect SFD using adsorptive stripping voltammetry (AdSV). The biochar was functionalized with HNO₃ (termed BCA) to enhance SFD preconcentration and was incorporated into two electrode platforms: carbon paste electrodes (CPEs) and screen-printed carbon electrodes (SPCEs). The preparation of each modified electrode (CPME-BCA and SPCE-BCA) was optimized to evaluate its analytical performance. Both BCA-modified electrodes exhibited significantly enhanced SFD oxidation signals compared to those of their unmodified counterparts. The optimized SPCE-BCA demonstrated a linear detection range from 5.0 × 10^–9 to 5.0 × 10^–6 mol L^–1, a limit of detection of 1.5 × 10^–9 mol L^–1, and high reproducibility, with an RSD of 4.92%. The sensor was successfully applied to spiked samples of tap water, synthetic urine, and low-fat milk, achieving recoveries of between 90.7 and 111%. This work highlights sugar cane bagasse-derived biochar as a cost-effective and eco-friendly material for electrochemical sensing. Notably, SPCE-BCA required less biochar for modification than CPME-BCA, offering a scalable solution for SFD monitoring in diverse matrices.