Rethinking data collection and signal processing. 2. Preserving the temporal fidelity of electrochemical measurements

Direct electrochemical measurements of biological events are often challenging because of the low signal relative to the magnitude of the background and noise. When choosing a data processing approach, the frequency and phase content of the data must be considered. Here, we employ a zero-phase (infinite impulse response (IIR)) filter to remove the noise from the analytical signal, while preserving the phase content. In fast-scan cyclic voltammetry, the frequency content of the signal is a function of the scan rate of the applied waveform. Fourier analysis was used to develop a relationship between scan rate and the filter cutoff frequency to maximize the reduction in noise, while not altering the true nature of the analytical signal. The zero-phase filter has the same effect as traditional filters with regards to increasing the signal-to-noise ratio. Because the zero-phase filter does not introduce a change to ΔE_peak, the heterogeneous electron rate transfer constant (0.10 cm/s) for ferrocene is calculated accurately. The zero-phase filter also improves electrochemical analysis of signaling molecules that have their oxidation potential close to the switching potential. Lastly, a quantitative approach to filtering amperometric traces of exocytosis based on the rise time was developed.