Polarography

PolarographyByYear

Heyrovského polarograf 1

Heyrovského polarograf 2

Polarography is an electroanalytical method used in analytical chemistry for the determination of the concentration of certain analytes in solution. It involves the measurement of the current that flows in an electrochemical cell under conditions of controlled potential. The technique was developed by Czech chemist Jaroslav Heyrovský in 1922, for which he received the Nobel Prize in Chemistry in 1959.

Principles of Polarography

Polarography is based on the principle of polarization of an electrode (the dropping mercury electrode, DME) in a solution containing ions. When a potential is applied to the DME, it causes the ions in the solution to be reduced or oxidized at the surface of the electrode. The current produced by this redox reaction is measured and plotted against the potential to produce a polarogram. The position and shape of the waves in the polarogram can be used to identify the analyte, while the wave height or area is proportional to its concentration.

Components of a Polarographic System

A typical polarographic setup includes a dropping mercury electrode as the working electrode, a reference electrode such as a calomel electrode, and a counter electrode. The system also includes a potentiostat to control the potential and a device to record the current-potential curve (polarogram).

Applications of Polarography

Polarography has been used in various fields such as environmental monitoring, pharmaceutical analysis, and the determination of metal ions and organic compounds in solution. It is particularly useful for the analysis of trace metals and organic compounds with multiple oxidation states.

Advantages and Limitations

One of the main advantages of polarography is its sensitivity and the ability to analyze complex mixtures. However, the method has limitations, including the use of mercury, which poses environmental and health risks, and interference from oxygen in the solution, which can affect the accuracy of the measurements.

Modern Developments

Due to the limitations associated with the use of mercury, alternative techniques such as voltammetry with solid electrodes have been developed. These techniques offer similar analytical capabilities without the use of toxic mercury.

Conclusion

Polarography has played a significant role in the development of electroanalytical chemistry. Despite its limitations and the advent of new techniques, it remains a fundamental method for the analysis of trace substances in solution.