Differential-pulse voltammetry (DPV) is a type of voltammetry that involves applying a series of voltage pulses to an electrochemical cell while measuring the resulting current. In DPV, the differential pulse or small potential pulses are superimposed on a linear potential sweep. The magnitude of these pulses is typically small, often in the millivolt range. Each voltage pulse lasts a short duration, usually in the order of a few milliseconds, and is applied at regular intervals along the potential sweep.
The basic principle of DPV is that applying a potential pulse to an electrochemical system generates a faradaic current, which arises from redox reactions occurring at the electrode surface. This faradaic current results from electron transfer between the electrode and the analyte species in the solution. The current is measured before and after each voltage pulse, and the difference between these two current values gives the differential current, which is plotted against the applied potential. The magnitude of this current is proportional to the concentration of the electroactive species present in the solution. DPV offers advantages like excellent resolution and relative inertness to capacitive currents. While the former makes distinguishing between multiple species present in a solution possible, the latter helps obscure the signal in other voltammetry techniques.
Square wave voltammetry applies a combined square wave and staircase potential to a stationary electrode. During the cathodic pulses, the analyte undergoes reduction at the electrode surface, while during the anodic pulses of the waveform, the reduced analyte is reoxidized. The square wave polarogram plots the current difference between two points in the square wave voltammogram. Typically, these points are chosen at the peak of the anodic and cathodic currents. The difference in current between the anodic and cathodic peaks in the square wave polarogram is proportional to the concentration of the analyte.
The limitations of linear-scan voltammetry are overcome using pulse methods like differential-pulse and square-wave voltammetry that measure faradaic current free of interfering charging current.
Differential-pulse voltammetry employs a sequence of potential pulses superimposed on a linear potential ramp. At each step, a pulse of higher potential is applied for a short duration, and the current is measured just before and at the end of the pulse.
The difference in current is plotted against the applied potential to generate a voltammogram. The maximum of this current is proportional to the concentration of the analyte in the solution.
Square wave voltammetry employs a waveform that combines a square wave and a staircase. In this process, the analyte is reduced at the electrode surface during cathodic pulses and reoxidized during anodic pulses.
The square wave polarogram measures the difference in current between two points.
As the two currents have opposing signs, the resultant current estimated from their difference is larger and is directly proportional to the concentration of the analyte.
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