Rethinking
Data Collection and Signal Processing.
2. Preserving the Temporal Fidelity of Electrochemical Measurements
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Abstract
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 Δ<i>E</i><sub>peak</sub>, 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