Background-subtraction of fast-scan cyclic staircase voltammetry at protein-modified carbon-fiber electrodes.

Background-subtraction techniques were applied to the voltammetry of nicotinamide adenine dinucleotide (NADH) at protein-modified carbon-fiber microelectrodes. The background currents at carbon-fiber electrodes were stable and voltammetric scans immediately before or after the analyte were effectively used for background subtraction. Digital step-potential waveforms were used to excite these carbon-fiber electrodes, where the resulting voltammetric analysis assessed the optimal switching and initial potentials and the electrochemical response time was determined. The initial potential was 0.0 V and the switching potential 1.1 V (versus Ag/AgCl) and the response time was approximately 300 ms. Some sensitivity to NADH was lost and voltammetric prescans were required at protein-modified electrodes to obtain a stable baseline. Current versus time was assessed by the average current of the faradaic region from each voltammogram and by differential current; the average current minus the current from a non-faradaic potential range. Differential current assessments discriminated against artifacts caused by pH (as high as 1.0 pH unit) and ionic strength flux (100 mM). These background-subtraction techniques allowed the faradaic information to be obtained quickly and conveniently while maximizing sensitivity and maintaining selectivity.