DifferentialPulseVoltammetry

Voltammetry in which small potential pulses (constant height 10 to 100 mV, constant width 10 to 100 ms) are superimposed onto a linearly varying potential or onto a staircase potential ramp. The current is sampled just before the onset of the pulse (e.g. 10 to 20 ms) and for the same sampling time just before the end of the pulse. The difference between the two sampled currents is plotted versus the potential applied before the pulse. Thus, a differential pulse voltammogram is peak-shaped. Differential pulse polarography is differential pulse voltammetry in which a dropping mercury electrode is used as the working electrode. A pulse is applied before the mechani- cally enforced end of the drop and the current is sampled twice: just before the onset of the pulse and just before its end. The pulse width is usually 10 to 20 % of the drop life. The drop dislodgement is synchronized with current sampling, which is carried out as in DPV. The ratio of faradaic current to charging current is enhanced and the negative influence of charging current is partially eliminated in the same way as in normal pulse voltammetry (NPV). Moreover, subtraction of the charging current sampled before the application of the pulse further decreases its negative influence. Due to the more enhanced signal (faradaic current) to noise (charging current) ratio, the limit of detection is lower than with NPV. The sensitivity of DPV depends on the reversibility of the electrode reaction of the analyte.