Instruction manual

ELECTRODE CHARACTERISTICS
Temperature Effects
The most common cause of error in pH measurement is temperature.
Ordinary electrodes drift with temperature changes. The Ross pH
Electrode eliminates the stability problems associated with the use of
conventional electrodes in samples of varying temperatures.
There are, however, two effects of temperature change that should
be kept in mind.
1. Electrode slope will change with varying temperature. This
slope change may be compensated for either manually, or,
automatically with an automatic temperature compensator
(ATC) probe and properly designed pH meter. Consult your pH
meter instruction manual for details.
2. Buffer and sample pH values vary with temperature because of
their temperature dependent chemical equilibrium. The
problem of differing pH values is easily solved by calibrating
the electrode with characterized standard buffers whose true
pH values at different temperatures are known. Buffer values at
different temperatures are given in Table 1. The problem of the
sample equilibrium varying with temperature in an
uncharacterizable manner will always remain. Therefore, pH
values should be reported along with the temperature at which
the measurement was made.
Electrode Leak Rate
The ground glass junction of the ROSS
™
Sure-Flow
®
Electrode has
been optimized to leak at a rate of approximately 1 mL per 24 hour
period. In order to keep the junction free, the leak rate is slightly
higher than conventional electrodes. The loss of filling solution is
minimal during the average time for a pH measurement and does
not contaminate samples.
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