Voltammetric determination of sulfonamides using paste electrodes based on various carbon nanomaterials

The authors have performed a comparative study of the performance of various carbonaceous material-based electrochemical sensors in order to identify the most appropriate sensor for determination of sulfonamides. The electro-oxidative power of carbon paste electrodes prepared using carbon black, graphite, carbon nanopowder, acetylene black, multiwalled carbon nanotubes and glassy carbon powder was investigated by square-wave voltammetry at pH 6.0 using sulfamethoxazole (SMX) as the model analyte. It is found that carbon paste electrodes prepared with graphite or carbon nanopowder and operated at a voltage of 0.93 (vs. Ag/AgCl) display the highest sensitivity and lowest detection limit. Next, the sulfonamides sulfadiazine, sulfacetamide, sulfa-dimethoxine, sulfathiazole, sulfamethiazole and sulfamerazine were also tested. The voltammetric response is linear in the 1 to 75 mu M concentrations range, with detection limits range from 0.4 to 1.2 mu M, and sensitivities were between 10 and 38 nA.mu M-1. The carbon nanopowder paste electrode (CNPE) showed the lowest detection limit (0.12 mu M) for SMX and was successfully applied to its determination in (spiked) water samples and in pharmaceutical formulation.