ELECTRODE CHARACTERISTICS
Electrode Response
The electrode potential plotted against concentration on
semilogarithmic paper results in a straight line with a slope of
about 54-60 mV per decade. See
Figure 1
The time response of the electrode, that is, the time required to
reach 99% of the stable potential reading, varies from several
seconds in concentrated solutions to several minutes near the
limit of detection. See
Figure 3.
Figure 3
Typical Electrode Response
To Step Changes in NaF Concentration
Reproducibility
Reproducibility is limited by factors such as temperature
fluctuations, drift, and noise. Within the electrode’s operating
range, reproducibility is independent of concentration. With
calibration every hour, direct electrode measurements
reproducible to ± 2% can be obtained.
33
time (minutes)
10
-
3
M to 10
-
6
M
10
-
3
M to 10
-
5
M
10
-
3
M to 10
-
4
M
10
-
3
M to 10
-
2
M
electrode
potential
(mV)
1
160
120
80
40
0
-40
-80
2
3
4
Summary of Contents for 96-09
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