10.3 : Interfacial Electrochemical Methods: Overview

Interfacial electrochemical methods focus on the phenomena occurring at the boundary between an electrode and a solution, as opposed to bulk methods that concentrate on the solution's overall properties. These interfacial methods are classified as either static or dynamic based on the presence of a nonzero current in the electrochemical cell and the consistency of analyte concentrations. Static methods, such as potentiometry, measure the cell's potential without any significant current passing through the electrodes, leaving the solution composition unchanged. In contrast, dynamic methods involve chemical reactions that alter the analyte concentrations and utilize a nonzero current in the cell. These dynamic methods are further categorized according to whether the current or potential is controlled while the other variable is adjusted. For example, controlled-current coulometry maintains a constant current to oxidize or reduce the analyte. On the other hand, amperometry—a controlled-potential method—monitors the current at a fixed potential, promoting the analyte's electrolysis reaction. Interfacial methods offer advantages such as speed, selectivity, sensitivity, and wide dynamic ranges (typically, 10^–3 to 10^–8 M), making them popular in various electroanalytical applications.