Polarography

Qualitative and quantitative analysis in Voltammetry
Voltammetry is an analytical technique based on the measure of the current
flowing through an electrode dipped in a solution containing electro-active
compounds, while a potential scanning is imposed upon it.
This electrode, is called working electrode and could be made with several
materials. Usually, it has a very little surface in order to assume quickly and
accurately the potential imposed by the electrical circuit. The electrode can be solid
(gold, platinum or glassy carbon) or formed by a drop of mercury hanging from a tip
of a capillary. If the electrode is formed by a drop of mercury rhythmically dropping
from a capillary, the analytical technique is called Polarography.
Voltammetry is a versatile technique for research purposes, it allow to search
into several aspects of the electrochemical reactions, namely those reactions in which
electrons exchanges are involved between reagents and products. For those reactions
it is possible to investigate on the laws governing the dependence of the current by
the potential imposed on an electrode dipped into the reaction environment.
Generally those laws are very complicated, just like the redox reactions and the
environment in which they take place are.
The use of the voltammetric techniques is the basis of the comprehension of
the laws concerning several electrochemical phenomena and has a great importance
in several thecnological fields, like:
- Research of corrosion proof materials (corrosion is a consequence of a
series of electro – chemical reactions)
- Research of new electrodic processes for chemical industries (in fact, for
example, million of tons of aluminium, chlorine, soda are produced by
means of electrochemical reactions)
- Production of new type of batteries that can store rapidly a great quantities
of energy.
One of the most important application of Voltammetry is the quantitative
analysis of trace of metals (or, anyway, of those reducible or oxidizable chemicals) at
?g/L levels or less.
This introduction deals with the quali – quantitative aspects of the
voltammetric analysis of trace of heavy metals and of organic substances in solution.