Conductometric sensors are chemical sensors that measure the electrical conductivity of an analyte or solution based on the concentration of that solution.
The device used for measuring conductivity is called a conductivity cell.
The conductivity measured is directly proportional to the concentration of the solution.
Principle of Conductometric Sensors
When an electric field is applied to the conductivity cell, the analyte dissociates into ionic species.
Ionic species movement:
Negative ions move towards the positive electrode.
Positive ions move towards the negative electrode.
This movement results in a change in electrical conductivity, which is measured by conductometric sensors.
Construction of Conductometric Sensors
Transducer: The conductivity cell is constructed using two platinum foils.
Features:
Unit cross-sectional area.
Unit distance (1 cm) between the two foils.
Volume: The volume between the two electrodes is 1 cm³ (1 cm² area and 1 cm distance).
Working Mechanism
Conductivity results from the dissociation of electrolytes into ions that migrate towards oppositely charged electrodes.
Applying a potential difference creates an electric field within the electrolyte, causing:
Dissociation of electrolytes into positive and negative ions.
Positive ions move towards cathodes and negative ions move towards anodes.
This movement results in the neutralization of both types of ions and the formation of neutral atoms or molecules.
The conductivity cell recognizes this chemical change and converts it into an electrical signal representing conductance.
Applications of Conductometric Sensors
Estimation of Acids and Bases: Used to estimate the concentration of acids, bases, and their mixtures.
Water Quality Testing: Checks the amount of ionic impurities in water samples. Measures acidity or alkalinity.
Enzyme-Catalyzed Reactions: Determines the amount of oxygen in water, analyte concentration, and enzyme activity.
Biotechnology and Agriculture: Applicable in various biotechnology and agricultural-related uses.