Designing an electrochemical sensor which is simple, cheap, sensitive, fast, and accurate is inevitable, as it is important in drug quality control, point-of-care diagnosis, and other clinical studies. Sensors for simultaneous determination of paracetamol, tryptophan, and caffeine have not been reported so far, and we report an electrochemical sensor via incorporating tin sulfide (SnS) and titanium dioxide (TiO 2 ) on graphene oxide (GO) sheets (SnS/TiO 2 @GO ternary composite) for their separate and simultaneous determination through cyclic voltammetry and differential pulse voltammetry techniques. The surface morphology and structural properties of the composite were characterized by analytical techniques. The electrochemical study of SnS/TiO 2 @GO composite modified glassy carbon electrode (GC-SnS/TiO 2 @GO) showed high activity toward the oxidation of paracetamol, tryptophan, and caffeine with significant decrease in overpotential due to large surface and high carrier mobility. The peak currents during separate determination of paracetamol, tryptophan, and caffeine increased linearly with the increase in concentration from 9.8 nM to 280 μM for paracetamol, from 13.3 nM to 157 μM for tryptophan, and from 16.6 nM to 333 μM for caffeine. The detection limit (3σ/S) was 7.5, 7.8, and 4.4 nM for paracetamol, tryptophan, and caffeine, respectively. The electron transfer coefficient (α), surface coverage concentration (Γ), number of electrons transferred (n), and diffusion coefficient (D) were calculated and discussed. The fabricated electrode showed low detection limit, wide linear range, and excellent reproducibility, selectivity, and stability. The study was also extended to the analysis of commercial tablets, beverage and human blood serum.Therefore, the present electrode holds great promise for identification and quantification of drugs in combination.
