Disposable electrochemical sensor based on shellac and graphite for sulfamethoxazole detection

Abstract The growth in the demand for mass analysis, in a fast and safe way, with good reliability and low cost has aroused great scientific interest in the search for new devices that prioritize precision and time. In this sense, this work presents a simple, disposable, and easy-to-use electrochemical sensor, developed on a waterproof paper substrate with a conductive ink based on shellac, a resin of natural origin, and graphite. The conductive ink was obtained through a simple mixture of its components and deposited on the paper substrate, being ready to use after a drying period. The new sensor was employed for the electrochemical detection of sulfamethoxazole (SMX), an antibiotic belonging to the class of sulfonamides, which presents great importance due to its direct impact on the flow of the food chain and is, therefore, commonly found as a metabolic residue in environmental and food samples. Using the differential pulse voltammetry technique, a linear range of 5.0 μmol L−1–100 μmol L−1 and a limit of detection of 0.4 μmol L−1 were obtained. The electrochemical sensor was also employed for the analysis of SMX in water and milk samples, and recovery values between 91 and 110% were obtained, proving that the development and application of the new conductive ink proposed for the fabrication of disposable devices provided an efficient electrochemical detection of SMX in the applied samples.