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Voltammetry is one of the main types of characterisation techniques in electrochemistry. While cyclic voltammetry is perhaps the most widely known, it is not the most powerful by far. In fact, for most applications, pulse voltammetry is preferred.
For this reason, we have briefly summarized the different pulse voltammetry techniques available to date in this post.
1. Normal Pulse Voltammetry (NPV)
First on our list we have NPV.
While this technique is not used as much as the other two it offers a unique advantage: it can remove the Cottrell behavior from the voltammogram.
Characterized by a series of increasing pulses superimposed on a DC potential, this technique, when appropriately optimized, is capable of resetting the redox state of the analytes after each pulse.
As a result, the peak-like shape of voltammograms switches to a sigmoid, because the depletion of the analyte is eliminated thanks to the pulsed waveform.
This unique characteristic of NPV makes it ideal for optimizing electrolysis potentials for continuous systems. So it is useful for optimizing glucose biosensors and electrolyzers.
2. Differential Pulse Voltammetry (DPV)
Second on our list we have DPV.
This technique is very efficient in removing the capacitive background from voltammograms, which makes it well suited for high-sensitivity assays.
This technique is characterized by small pulses superimposed on a linear potential sweep.
When collecting the data, the current just before the pulse and at the end of the pulse are subtracted to construct the voltammogram. Thus the name “differential” voltammetry.
Some common applications of DPV are immunoassays and heavy metal detection.
3. Square Wave Voltammetry
Last but not least, we have SWV.
While initially developed to obtain full voltammetric data from dropping mercury electrodes within a single drop, SWV has proved to be a powerful technique.
Faster than DPV and NPV, SWV is able to acquire reliable full voltammetric data within seconds.
Unlike cyclic voltammetry, SWV outputs two current-potential datasets, the so-called Forward and Reverse currents. These two datasets can be subtracted to eliminate/minimize the capacitive background signal, leading to an enhanced Faradic peak similar to the one obtained in DPV.
Thus, from all 3 techniques, SWV is perhaps the most versatile and fast, but also the most complex to acquire. That’s why, with the improvement in integrated electronics, SWV is gaining traction in research once again.
At Macias Sensors, we have used SWV with multiple clients developing biosensors thanks to its advantages.
One interesting twist from SWV is that it can be further enhanced by turning it into a pulsed equivalent of cyclic voltammetry. This is the so-called cyclic SWV.
In cyclic SWV, the pulsed voltammogram is recorded in both directions. This results in a data collection rate that is 2x faster than that of cyclic voltammetry at the same scan rates. Moreover, since the potentials are swept back and forth, the redox state within the diffusion layer is restored. This is particularly interesting for applications where periodic measurements are required, Otherwise, it is necessary to apply conditioning potentials at the beginning of each of the measurements to ensure reproducible results.
In summary, pulse voltammetry techniques offer unique advantages over traditional voltammetric techniques such as cyclic voltammetry or linear sweep voltammetry. Thanks to the unique data acquisition strategies of pulsed techniques it is possible to eliminate capacitive backgrounds and Cottrell behaviors, increase sensitivity and speed up data acquisition.
If you would like to learn more about each of these techniques, check our blog. We publish content regularly about electrochemistry and biosensors.