Ionode IJ pH V5.1 - Manual (Page 11)

Ionode IJ Instruction Manual 11
If the restriction becomes clogged and
movement of ions becomes inhibited, the
electrode will appear to be stable in buffer
solutions, but it may produce errors in non-ideal
and low buffering capacity samples. The IJ
reference system overcomes this by allowing
free movement of ions past the restriction,
allowing the junction to be cleaned and the
sleeve electrolyte to be easily replaced. The
result is a reference electrode system of
assured reliability (see Figure 10b).
References:
1)
John A. Illingworth “A common source of
error in pH measurement”, Biochem. J.,
(1981) 195, p. 259-262.
4.2.2. Output
The voltage output is related to the hydrogen
ion activity by the Nernst equation:
 
] [ ln
0
  
H
nF
RT
E E
This can be rewritten in linear form by
substituting in the definition of pH and grouping
all the constants to give:
 
pH T SLOPE E E
 


0
E
0
’
is referred to as the isopotential point.
Theoretically, it is the pH which has no
temperature dependence.
The IJ44 has been designed so that it is
compatible with all modern pH meter