Polarographic

Polarographic refers to polarography, an electrochemical method used for trace analysis and chemical characterization by measuring current as a function of applied potential. The technique was developed in the 1920s by Jaroslav Heyrovský, who pioneered the approach and later received the Nobel Prize in Chemistry in 1959 for his work on electrochemical methods.

Polarography commonly employs a three-electrode cell, with a dropping mercury electrode or, in some variants, a mercury film electrode as the working electrode, together with a reference electrode and a counter electrode. The potential is swept or stepped, and the resulting current is recorded to produce a polarogram. In the classic dropping mercury electrode polarography, the current is diffusion-controlled and rises to a limiting current. The limiting current is proportional to the concentration of reducible species, and the half-wave potential provides information about the redox potential of the species. Variants such as normal polarography and differential-pulse polarography offer different sensitivity and resolution.

Applications of polarographic analysis include trace metal determination (for example cadmium, lead, copper, and zinc) and the analysis of various organic and inorganic compounds. The use of the renewing mercury drop surface helps mitigate fouling in many analyses, and the technique requires careful control of pH and supporting electrolyte. Interfering species or complexing agents can complicate interpretation.

Limitations of polarography include reliance on mercury electrodes, which pose environmental and safety concerns, and restricted applicability for species that do not exhibit reversible or near-reversible reductions under the assay conditions. With advances in voltammetry on solid electrodes and modern instrumentation, polarography has been largely superseded for routine analyses, though its principles and certain variants remain relevant in education and specialized practice.