ANODIC STRIPPING VOLTAMMETRY (ASV)

Voltammetry comprises a group of electroanalytical methods in which information about the analyte is derived from the measurement of current as a function of applied potential. It is based upon the measurement of a current that develops in an electrochemical cell under conditions of complete polarization. The potential of the polarizable working electrode serves as a driving force for the electrochemical reaction. The working electrode varies as the activity of the analyte changes. It is the electrode at which the analyte is oxidized or reduced.

The reference electrode provide a constant potential that does not change during the potential measurement (potential is known). The counter electrode is the electrode coupled to the working electrode but plays no part in determining the magnitude of the potential being measured.

The resulting current is known as “faradaic current” which obeys Faraday’s Law. The two factors that governs the current are the mass transport and charge transfer. Mass transfer is the rate of movement from the bulk of the solution to the electrode surface. Charge transfer is the rate of transfer from electrode to the solution species and vice versa.

Stripping involves deposition of the analyte in microelectrode. It involves electrodeposition, equilibration and stripping step. After time, the electrolysis is discontinued, stirring is stopped, and the deposited analyte is determined by voltammetric procedures. Stirring helps deposition of the analyte on the electrode. In anodic stripping, the electrode behaves as cathode during deposition step and an anode during stripping step, with the analyte being oxidized back to its original form. Cathodic stripping on the other hand, the electrode behaves as an anode during the deposition step and a cathode during stripping.

 Theoretically, deposition is allowed to occur during a carefully measured period. The electrolysis period is determined by the sensitivity of the method ultimately employed for the completion of the analysis. The unknown sample was analyzed using stripping by standard addition technique.
Some applications of voltammetry are the determination of metal ion concentrations in water and kinetic studies of reactions specifically studies about oxidation and reduction processes in various media.

References:
Skoog, D.A., et al. 2004. Fundamentals of Analytical Chemistry. 8th ed. Singapore: Brooks/Cole.
Chemistry 137.1. 2006. Modern Analytical Chemistry Manual. Institute of Chemistry, College of Arts and Sciences, University of Philippines College Laguna.