Fast pulsed amperometric waveform for miniaturised flow-through electrochemical detection: Application in monitoring graphene oxide reduction

A fast pulsed waveform (2-steps at +400 mV and −400 mV, 10 ms each, 50 Hz cycle repetition) was developed incorporated within a miniaturised EC detector, and used to demonstrate the pulsed amperometric detection (PAD) of hydrazine in a flow-based analytical system. In contrast to standard amperometric detection (AD), a subsequent surface oxide reduction step was applied within the PAD waveform. The PAD applied within a simple flow-injection analysis (FIA) method provided a limit of detection (LOD) just as low as 0.8 nM of hydrazine (RSD 5%, n = 9, linearity r² = 0.99 for 1 nM-100 μM), which is one order of magnitude lower than the lowest LOD reported todate. Significantly, the LOD was obtained using 5–20 times lower electrode surface area, flow rate, and sample volume, than in previous methods, with 15 times faster cycle repetition frequency than alternative PAD based studies reported in literature. Practical application of the PAD waveform was demonstrated by monitoring the temporal consumption of reducing agents during graphene oxide reduction experiments, separated using chromatographic methods (hydrazine in IC and ascorbic acid in HPLC).