E = Eo - 0.05915/z log (a(red)/a(ox))
E = +1.2288 - 0.05915/4 log (a2(H2O)/a(O2(g))a4(H+))
E = +1.2288 + 0.0148 log a(O2(g)) + 0.05915 log a(H+)
E= +1.2288 + 0.0148 log p(O2(g)) - 0.05915 pH
The actual potential of the oxygen electrode will then vary with two
factors: the partial pressure of the oxygen gas,
and the acidity of the solution in which the electrode is operating.
Each exerts its influence on the potential
independently of the other, and the observed electrode potential is a
result of both influences. This is true in
general of all multiple influences on potential which arise from the Nernst
relationship -- they can be considered to act independently.
[http://www.chem.ualberta.ca/courses/plambeck/p102/p02104.htm]
Polarographic Oxygen Monitoring
How does your polarographic dissolved oxygen system work?
The Clark type polarographic electrode was developed by Dr. Leland Clark.
When a potential of about 0.7V is applied between the anode and the cathode,
dissolved gaseous oxygen is reduced at the platinum cathode.
This produces a current and consumes the oxygen in the immediate vicinity of the
exposed platinum cathode. Oxygen in the sample volume diffuses through the membrane
to the oxygen-poor region between the membrane and the electrode. When a steady-state
is reached (which usually happens in less than 4 seconds), the electrode current is
proportional to the rate of arrival of oxygen molecules at the cathode, which is in turn
proportional to the concentration of oxygen outside the membrane.
[http://www.instechlabs.com/oxygen.html]