19
Fluoride Ion Selective Electrode User Guide
Direct Calibration Using a Meter with a Millivolt Mode
1. Adjust the meter to measure mV.
2. Measure 50 mL of the less concentrated standard and
50 mL of TISAB II and add the standard and TISAB II to a
150 mL beaker. Stir the solution thoroughly.
3. Rinse the electrode with deionized water, blot dry and place
into the beaker with the less concentrated standard. When
a stable reading is displayed, record the mV value and
corresponding standard concentration.
4. Measure 50 mL of the more concentrated standard and
50 mL of TISAB II and add the standard and TISAB II to a
second 150 mL beaker. Stir the solution thoroughly.
5. Rinse the electrode with deionized water, blot dry and
place into the beaker with the more concentrated standard.
When a stable reading is displayed, record the mV value
and corresponding standard concentration.
6. Using a calculator or electronic spreadsheet, prepare
a calibration curve by graphing the log of the fl uoride
concentration against the millivolt value readings.
7. Measure 50 mL of the sample and 50 mL of TISAB II and
add the sample and TISAB II to a clean 150 mL beaker. Stir
the solution thoroughly.
8. Rinse the electrode with deionized water, blot dry and place
into the beaker. When a stable reading is displayed, record
the mV value.
9. Using the calibration curve prepared in step 6, determine
the unknown concentration of the sample.
Note:
If using TISAB III, add 5 mL of TISAB III to the 50 mL of
standard or sample in step 2, step 4 and step 7.
