Thermo Fisher Scientific Ion Selective Electrodes Fluoride - Manual (Page 5)

Instruction Manual Fluoride Electrode
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5.
Eutech Total Ionic Strength Adjuster Buffer (TISAB 1), Code No. EC-ISA-FL1-BT.
TISAB 1 is used to adjust the pH of the solution, de-complex fluoride and provide a
constant background ionic strength. To prepare this solution from your own laboratory
stock, half fill a four liter beaker with distilled water. Place the beaker on a magnetic
stirrer, add a large stirring bar, and begin stirring. Slowly add 230 ml of concentrated
acetic acid, 232 grams of reagent-grade sodium chloride, and 16 grams of reagent-grade
CDTA. After the solids have dissolved, allow the solution to cool to room temperature.
Slowly add 150 grams of reagent-grade sodium hydroxide. After the solids have dissolved,
allow the solution to cool to room temperature. Calibrate a pH electrode and adjust the pH
to 5.25 with small addition of 5 M NaOH. Fill to the mark with distilled water.
6.
Eutech Low Level Total Ionic Strength Adjuster Buffer (TISAB 2), Code No. EC-ISA-
FL2-BT. Use when measuring in samples containing less than 2X10
-5
M (0.4 ppm) fluoride
and containing no fluoride complexing agents. To prepare this solution from your own
laboratory stock, place about 2'000 ml distilled water in a four liter beaker. Add 57 ml
glacial acetic acid and 58 grams sodium chloride. Place the beaker on a magnetic stirrer,
add a stirring bar and begin stirring. Immerse a calibrated pH electrode into the solution.
Slowly add 5 M NaOH until the pH is 5.25. Allow the solution to cool and fill to the mark
with distilled water.
GENERAL PREPARATION
Electrode Preparation
Remove the rubber caps covering the electrode tips and the rubber insert covering the filling hole of
the reference electrode. Fill the combination electrode or the reference electrode with the filling
solution shipped with the electrode to a level just below the fill hole. No preparation is required
with a sealed reference electrode. Connect the electrodes to the proper terminals of the meter as
recommended by the meter manufacturer.
Electrode Slope Check (with pH/mV meter)
(Check electrodes each day)
1. To a 150 ml plastic beaker, add 50 ml of distilled water and 50 ml of TISAB. Place the
beaker on a magnetic stirrer and begin stirring at a constant rate. After assuring that the
meter is in the millivolt mode, lower the electrode tips into the solution.
2.
Using a pipet, add 1 ml of 0.1M, 1,000 ppm, or 100 ppm fluoride standard to the beaker.
When the reading has stabilized, record the mV reading.
3.
Using a pipet, add 10 ml of the same fluoride standard used above to the beaker. When the
reading has stabilized, record the mV reading.
4.
Determine the difference between the two readings. The electrode is operating correctly if
the millivolt potential has changed by 57±2 mV, assuming the solution temperature is
between 20o and 25oC. See the
TROUBLESHOOTING section if the potential change is not
within this range.