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Saturday, March 15, 2014

Electrochemical Detection Methods


There are 3 types of Electrochemical Detection Methods
  1. Amperometric Method
  2. Potentiometric Method 
  3. Conductimetric Method
Amperometric Detection Method

Amperometric Method of detection is by measuring the current. In amperometric detection, oxidation or reduction of analyte at the working electrode takes place. The oxidation or reduction of the analyte resulting in the gain or loss of electrons at the electrode surface. The electric current generated due to the electrons passed to or from the electrode can be recorded and it will be proportional to the analyte concentration.



Oxidation is mostly employed mode since dissolved oxygen interferes in the reduction.

Principle of Ampermetric Detection


The analyte bound to the receptor will undergo oxidation reduction reaction that can be quantified by measuring the electron exchange from working electrode to the counter electrode.


The current measured in the amperometric detection is relate to

  • Electrode Area, 
  • No of electrons exchanged, 
  • Faraday constant, 
  • Diffusion coefficient,
  • Thickness of the diffusion layer 
  • Concentration of the species
Applications
  • Glucose Biosensors


Potentiometric Detection Method

Potentiometric Detection method is based on the measurement of Nernst potential either across an ion selective barrier or at an electrode surface with respect to a reference electrode.



Potentiometric Detection Measures the voltage between the working electrode and the reference electrode

In potentiometric Detection method, ion selective electrodes are used as sensors.

Application

Oxygen Sensors

pH determination

Conductimetric Detection Method





Conductimetric Detection is based on the measurement of the conductivity
or resistance of a solution between two indicator electrodes 
when a small current is applied to them.

Most widely used in ion chromatography.