NormalPulseVoltammetry

Voltammetry in which potential pulses of amplitude increasing by a constant increment and with a pulse width of 2 to 200 ms are superimposed on a constant initial potential. Normal pulse polarography is NPV in which a dropping mercury electrode is used as the working electrode. A pulse is applied just before the mechanically enforced end of the drop. The pulse width is usually 10 to 20 % of the drop time. The drop dislodgment is synchro- nized with current sampling, which is carried out just before the end of the pulse, as in NPV. Sigmoidal wave-shaped voltammograms are obtained. The current is sampled at the end of the pulse and then plotted versus the potential of the pulse. The current is sampled just before the end of the pulse, when the charging current is greatly diminished. In this way, the ratio of faradaic current to charging current is enhanced and the negative influence of charging current is partially eliminated. Due to the improved signal (faradaic current) to noise (charging current) ratio, the limit of detec- tion is lowered. The sensitivity of NPV is not affected by the reversibility of the electrode reaction of the analyte.