Electroanalytical study of sulfa drugs at diamond electrodes and their determination by HPLC with amperometric detection

Conductive boron-doped diamond thin film electrodes were examined for the e lectroanalysis of three sulfa drugs, sulfadiazine, sulfamerazine and sulfam ethazine. Cyclic voltammetry, flow injection analysis and liquid chromatogr aphy with electrochemical detection were used to study the oxidation reacti ons. At diamond electrodes, highly reproducible and well-defined cyclic vol tammograms were obtained for all three drugs with a signal to background (S /B) ratio of a factor of ten greater than that obtained at two types of fre shly polished glassy carbon (GC) electrodes. Diamond exhibited a highly rep roducible amperometric response, with a peak variation of similar to 5%, ev en at a concentration of 100 nM. A detection limit of 50 nM and a linear dy namic range of three orders of magnitude were obtained. No fouling of the e lectrode was observed within the experimental period of several hours. A ra pid stabilization of the background current is achieved, within 10 min afte r the application of the operating potential under flow conditions, unlike the case of GC electrodes, which requires more than 30 min for reasonable s tabilization. We have demonstrated the application of the diamond electrode for the simple and sensitive amperometric detection of the sulfa drugs in a standard mixture after their separation with reverse-phase HPLC to produc e chromatograms with a flat baseline and high reproducibility, even at conc entrations as low as 100 nM. (C) 2000 Elsevier Science B.V. All rights rese rved.