Measurement Principle Of Ion Selective Electrode; Measurement Principle Of Ion; Selective Electrode - Horiba Scientific 6560S-10C Instruction Manual

M
easurement principle of ion

selective electrode

If specific ions exist in the sample solution, the ion selective membrane of the
ion selective electrode generates a potential that corresponds to the
concentration of those ions. The generated potential is measured as the
potential difference on the basis of the reference electrode using an ion meter
or meter with an ion measurement function.
The measured potential difference and the logarithm of the concentration
(activity) (
in a proportional relationship which can be represented by the following
equation.
E = E + (2.303 RT/nF) logC
0
E: Measured electrode potential (V)
E : Reference potential depending on the ion selective electrode (V)
0
(The reference potential of the reference electrode and the potential
difference of the liquid junction are included.)
F: Faraday constant (96480 C mol
R: Gas constant (8.314 JK
T: Absolute temperature (K)
n: Ion charge number
:
Activity coefficient (
C: Ion concentration
This equation is called the Nernst equation, and is the base of ion concentration
measurement using an ion selective electrode.
(2.303 RT/nF) is the change of the electrode potential generated when the ion
concentration (activity) is changed by a factor of ten times, and is referred to as
the sensitivity, potential gradient, slope, or Nernst coefficient.
According to the above equation, if the potential gradient is determined by the
calibration using the standard solutions, the concentration (activity) A of the
targeted ions can be measured by obtaining electrode potential E of the ion
selective electrode in the sample solution.
58
Page 60) of the ions to be measured in the sample solution are
-1
mol
Page 60)
-1
)
-1
)