18
Fluoride Ion Selective Electrode User Guide
Direct Calibration Using a Meter with an ISE Mode
Note:
See the meter user guide for more specifi c information.
1. Measure 50 mL of the less concentrated standard and
50 mL of TISAB II and pour into a 150 mL beaker. Stir the
solution thoroughly.
2. Rinse the electrode with deionized water, blot dry and place
into the beaker with the less concentrated standard. Wait
for a stable reading and then adjust the meter to display the
value of the standard, as described in the meter user guide.
3. Measure 50 mL of the more concentrated standard and
50 mL of TISAB II and pour into a second 150 mL beaker.
Stir the solution thoroughly.
4. Rinse the electrode with deionized water, blot dry and place
into the beaker with the more concentrated standard. Wait
for a stable reading and then adjust the meter to display
the value of the second standard, as described in the meter
user guide.
5. Record the resulting slope value. The slope should be
between -54 to -60 mV when the standards are between
20-25 ˚C. When using a Thermo Scientifi c meter with the
Autoblank function enabled, the absolute value of the slope
should be greater than 54 mV.
6. Measure 50 mL of the sample and 50 mL of TISAB II (or
either low-level TISAB or TISAB IV) and pour into a clean 150
mL beaker. Stir the solution thoroughly.
7.
Rinse the electrode with deionized water, blot dry and place
into the sample. The concentration of the sample will be
displayed on the meter.
Note:
If using TISAB III, add 5 mL of TISAB III to the 50 mL of
standard or sample in step 1, step 3 and step 6.
