Sinusoidal voltammetry: a frequency based electrochemical detection technique

Sinusoidal voltammetry is an electrochemical technique, which uses a large amplitude sinusoid as the potential waveform and performs data analysis in the frequency domain. When the amplitude of the applied potential waveform is large (i.e. > 50 mV) the current-potential behavior of the electrochemical interface is extremely non-linear. As a result the faradaic response exhibits signal intensity at higher order harmonics of the fundamental excitation frequency. In contrast, the major source of noise, due to the capacitive charging current, is primarily linear and the vast majority of its intensity remains at the fundamental frequency. The dramatic difference in the frequency response between these signals can be exploited in many ways to enhance both the signal-to-noise ratio and selectivity of an electrochemical measurement. The extent of faradaic signal distribution to the harmonics of the fundamental excitation frequency is dependant on many standard voltammetric parameters. In addition to enhanced sensitivity at the higher harmonics, redox species with different electrochemical properties (e.g. E-o number of electrons, electron transfer rate constant, etc.) can be detected selectively based on their unique `fingerprint' frequency response. The experimental parameters (e.g. E-switch, scan rate, excitation potential window amplitude, etc.) can be optimized, as well as the frequency and phase angle to achieve the best selectivity for the analyte of interest. (C) 2002 Published by Elsevier Science B.V.