A lab-made stencil-printed electrode with silver nanoparticle-modified graphite for the determination of the...

Environmental contamination by antibiotics, resulting from their inadequate use and disposal, causes significant alarm and poses a serious threat to public health. The persistence of these residues in soil and water resources promotes the development of microbial populations undermining the efficacy of clinical treatment. Sulfamethoxazole (SMZ) is an antibiotic from the sulfonamide group that is used therapeutically and is incompletely metabolized, which contributes to its spread in the environment. Thus, this study presents a cost-effective electrochemical sensor for the determination of SMZ in different samples. The electrode was produced using powdered graphite modified with silver nanoparticles (AgNPs), resulting in a conductive ink that was deposited on the PET sheet substrate using the stencil-printed method. The sensor named AgNPs@Gr/StPE was characterized morphologically, spectroscopically and electrochemically, proving the catalytic effect promoted by the AgNPs. A square wave voltammetry method was optimized, showing an excellent linear response between 10 and 70 µmol L^-1, as well as good detectability (detection limit of 1.51 µmol L^-1). Furthermore, the method showed good precision (RSD < 3.7%) and accuracy with recoveries ranging from 92 to 107% for spiked river water, honey and synthetic urine samples. The proposed device showed robust stability over time and excellent selectivity in the presence of other antibiotics and components of the sample matrix. Therefore, the proposed sensor is a promising, simple, cost-effective and efficient alternative for electroanalysis of emerging contaminants.