Voltammetric determination of antibacterial nitro-compounds at activated carbon fibre microelectrodes

The electrochemical behavior of the nitrofuran antibiotics nitrofurantoin (NFA) and nitrofurazone (NFZ), as well as the related nitroimidazole drug, metronidazole (MNZ) at electrochemically activated carbon fibre microelectrodes (CFMEs) is reported. These nitrofurans have been widely used in the form of feed additives for the treatment of gastrointestinal infections in cattle, pigs and poultry. Electrochemical activation of CFMEs by repetitive square-wave (SW) voltammetric scans between 0.0 and + 2.6 V, produced an unexpected high cathodic response from these compounds. This is attributed to the increase of the carbon fibre surface area due to its fracture and the appearance of deep fissures along the main fibre axis. Penetration of the nitroderivative compounds into the micro-channels of the activated fibres was profited to develop a sensitive and selective method for NFA based on stripping SW voltammetry. The metabolite of NFA, 1-aminohydantoin (AHD), did not exhibit cathodic response in the potential range between - 0.9 and + 0.1 V However, AHD gave a SW oxidation signal at activated CFMEs, with a potential of + 0.95 V, which did not appear at non-activated microelectrodes. Based on this finding, the simultaneous determination of NFA and AHD was performed by amperometry using two activated CFMEs in a parallel configuration connected to a multichannel detector. This methodology was also used to carry out degradation studies of NFA in acidic and basic media under photodegradation or thermal degradation conditions.