Julia Oliveira Fernandes, Cassiano Augusto Rolim Bernardino, Francisco Walison Lima Silva, Claudio Sabbatini Capella Lopes, Cláudio Fernando Mahler, Márcia Cristina da Cunha Veloso, Gilberto Alves Romeiro, B S Archanjo, Ricardo Erthal Santelli, Fernando Henrique Cincotto
Abstract This study presents the development of a novel, disposable, and eco-friendly electrochemical device based on biochar-modified screen-printed electrodes (SPE/BC) for the detection of the antibiotic trimethoprim. Biochar, derived from sewage sludge, was applied as a nanomaterial to enhance the sensitivity of the sensor for trimethoprim quantification in environmental, biological, and pharmaceutical samples. Characterization techniques, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy, were used to assess the properties of biochar. Surface area, pore volume, and pore diameter were measured using the Brunauer–Emmett–Teller method. The electrochemical sensor performance was analyzed using impedance spectroscopy, cyclic voltammetry, and differential pulse voltammetry, revealing a strong synergistic effect on the trimethoprim oxidation process. The device showed high sensitivity with a detection limit of 71.0 nmol L⁻ 1 over a linear range of 1.75–231.43 μmol L⁻ 1 . Recovery studies in synthetic urine, tap water, and pharmaceutical tablets demonstrated recoveries of 92%–99%, with no sample pretreatment. The sensor exhibited selectivity towards common interferents such as sulfamethoxazole, urea, and ascorbic acid, making it a practical tool for detecting trimethoprim as an emerging pollutant. Graphical Abstract