Theory:

Pulse voltammetry methods can be coupled with a pre-concentration step ‌to enrich the electrode surface with the analyte of interest, followed by a pulse anodic stripping voltammetry (ASV). It is a voltammetric method for the quantitative determination of specific ionic species. ASV itself is an attractive technique for rapid and sensitive determination of trace metals in solution. The main advantage of this method is the excellent limit of detection (LOD) that can be reached (in the ppb range) and it’s all because of the efficient removal of the capacitive current since the current is sampled at the end of the pulse potential, where the faradaic current is predominant.

ASV or DPASV are widely used especially where high sensitivity is necessary. Nanomolar (10^-9M) or part per trillion (ppt) detection is achievable using ASV. The metal ions being analyzed are first reduced into a hanging mercury drop electrode for a fixed period. This reduction is performed at a cathodic applied potential E_app sufficiently negative to ensure the reduction of all metal ions of interest. The number of metal ions dissolved into mercury drop as elemental metal depends linearly on this “Deposition time’’. It involves a deposition step, at an applied negative potential, for a specified period. The metals as ions in solution are concentrated by plating them onto the electrode in metallic forms. Then the electrode is scanned linearly towards the positive potential so that the metals one at a time are stripped from the electrode and re-oxidized at a potential characteristic of each metal. Differential pulse anodic stripping voltammetry or DPASV is an advanced form of anodic stripping voltammetry because of its lower detection limit. In DPASV, the staircase sweep potential is superimposed on both step potential pulses, causing a continuous increase in the base potential. By sampling the forward (i_f) and backward (i_b) current, the plot of the difference of current (i_f − i_b) as a function of the applied potential can be obtained.