A new and simple method for the simultaneous determination of amoxicillin and nimesulide using carbon black within a dihexadecylphosphate film as electrochemical sensor

Abstract The first electroanalytical method for the simultaneous determination of an important antibiotic (amoxicillin – AMX) and an anti-inflammatory drug (nimesulide –NIM), widely used in combination, is here proposed. In this method, a glassy carbon (GC) substrate modified with carbon black (CB) immobilized within a dihexadecylphosphate (DHP) film is used as electrochemical sensor (CB–DHP/GC). The electrochemical activity of this sensor was assessed (comparatively to that of GC) by electrochemical impedance spectroscopy, using the [Fe(CN) 6 ] 3–/4– redox couple, when two different active electron transfer regions were clearly characterized. Using square-wave voltammetry and a 0.2 mol L −1 phosphate buffer (pH 7.0) as supporting electrolyte, a separation of ca. 180 mV between the oxidation peak potentials of AMX and NIM was obtained with the novel CB–DHP/GC sensor, and the obtained detection limits for AMX and NIM were 0.12 μmol L −1 and 0.016 μmol L −1 , respectively. This new electroanalytical method was successfully applied in the simultaneous determination of AMX and NIM in biological urine and environmental samples. The here-proposed method is of great analytical interest, as it is faster and cheaper than the only other method (based on HPLC) reported in the literature for the simultaneous determination of these drugs.