10.21 : ボルタンメトリー技術: パルスボルタンメトリー

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.