Surface and kinetic enhancement of selectivity and sensitivity in analysis with fast scan voltammetry at scan rates above 1000 V/s

Selectivity and sensitivity in the determination of low concentrations of dopamine (cation) in the presence of large excess of ascorbic acid (anion), and in the determination of low concentrations of uric acid in the presence of ascorbic acid, has been investigated by fast scan voltammetry at bare electrodes. In spite of similar reaction potentials of dopamine and ascorbic acid, selectivity to dopamine can be substantially improved at a bare electrode by pushing the scan rate up to 10000 V/s. Determination of dopamine in the presence of 1000 fold excess of ascorbic acid is possible at high scan rates because of the differences in the electrochemical kinetics of the two probes. In addition, fast scan voltammetry at bare electrodes can achieve improved selectivity to uric acid (anion) in the presence of ascorbic acid (anion). The effect of the method of electrode surface treatment on response (peak separation and peak current in voltammetry) to dopamine and uric acid is also discussed. Signalto-noise ratios at bare electrodes can be improved in fast scan methods because of the high temporal resolution of the method which allows acquisition of a large number of scans which can be signal averaged in a short period of time. In addition, because voltammetric peak current increases with scan rate, large signals can be measured. The limitations of fast scan voltammetry at bare electrodes are also discussed, such as the requirement for accurate background subtraction and the limited digital resolution which results from high background currents.