Reduction in size by electrochemical pre-treatment at high negative potentials of the background currents obtained at negative potentials at glassy carbon electrodes and its application in the reductive flow injection amperometric determination of nitrofurantoin

Abstract

The reduction of dissolved molecular oxygen at a glassy carbon electrode was shown to be made more difficult on electrochemically pre-treating a newly polished glassy carbon disc electrode (3 mm in diameter) in 0.1 M sulphuric acid solution at –2.7 V for 1 min. By this means a background current of only 1 µA was obtained when this electrode was held at –1.05 V in a flow injection system incorporating extensive PTFE transmission tubing and using a deoxygenated pH 7 Britton-Robinson buffer as eluent (flow-rate 6.5 ml min^–1). The size of the signal obtained when 100 µl of eluent that had not been deoxygenated were injected as the sample blank was only 0.02 µA at –0.7 V. When nitrofurantoin was determined using these latter conditions, this blank signal was equivalent to about 2 × 10^–7M nitrofurantoin.