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Module 5 : Electrochemistry

Lecture 24 : Applications of Electrode Potentials

24.6

Electrochemical sensors

Sensors are beginning to play an increasingly important role in our daily lives, particularly in chemical, biochemical, optical and mechanical applications. We will comment here on some features of electrochemical and biochemical sensors. Electrochemical sensors employ potentiometric, amperometric and conductometric measurements. Among the major potentiometric sensors are ion selective electrodes and electrodes that depend on the concentration differences in electrolytes (e.g. potentionmetric solid electrolyte sensor).

The ion selective electrodes (ISEs) are sensitive to ions such as Na⁺, K⁺, Li⁺, Ca²⁺, Cl^-, HS^-, HPO₄^- and pH. Some of them use coated wire electrodes wherein the coating can be an ion selective polymer membrane. These sensors can be miniaturized. In biomedical monitoring (immunosensors) ion selective field effect transistors have been used. Multisensors that are capable of detecting multiple ions use microelectronics. These can be used in vivo. The sensitivity required in these sensors is 10^-4 V. Some of the techniques that are useful in the development of sensors are cyclic voltametry, linear sweep voltametry, chronoamperometry, chronopotentionmetry and electrochemical impedance spectroscopy. You may read about these from your technical libraries.