15
Fluoride Ion Selective Electrode User Guide
Typical Calibration Curve
In the direct calibration procedure, a calibration curve is
constructed either in the meter memory or in an electronic
spreadsheet and graphing the log of the fl uoride concentration
against the millivolt value readings. Electrode potentials of
standard solutions are measured and plotted on the linear
axis against their concentrations on the log axis. In the linear
regions of the curves, only two standards are needed to
determine a calibration curve. In non-linear regions, more points
must be taken. These direct calibration procedures are given for
concentrations in the region of linear electrode response. Low
level measurement procedures are given in the next section for
measurements in the non-linear region.
10
-
5
0.1
180
160
140
120
100
80
60
40
20
0
-20
-40
-60
1
10
100
1000
10
-
4
10
-
3
10
-
2
10
-
1
molarity
ppm fluoride as F
-
10-fold change
electrode
potential
(mV)
-54 to -60 mV
Figure 2 Typical Calibration Curve
