4
Fluoride Ion Selective Electrode User Guide
8. Total Ionic Strength Adjustment Buffer (TISAB),
which provides a constant background ionic strength,
decomplexes fl uoride ions and adjusts the solution pH.
Cat. No.
Description
940909
TISAB II, 3.8 L bottle
940999
TISAB II, 4 x 3.8 L bottle
940911
TISAB III concentrate, 475 mL bottle
Low-Level TISAB
For use when measuring in samples containing less than 0.4
ppm (2 x 10
-5
M) fl uoride and no fl uoride complexing agents such
as iron or aluminum are present.
To prepare low level TISAB: Place 500 mL of distilled water in
a 1 liter beaker. Add 57 mL of glacial acetic acid and 58 g of
reagent grade sodium chloride to the beaker. Place the beaker
in a water bath for cooling. Immerse a calibrated pH electrode
into the solution and slowly add 5 M NaOH until the pH is
between 5.0 and 5.5. Cool the solution to room temperature.
Pour the solution into a 1 liter volumetric fl ask and dilute to the
fl ask mark with distilled water. All reagents must be as pure as
possible to keep the fl uoride level low in the buffer.
Use as directed for TISAB II; combine equal volumes of low level
TISAB and sample or standard before taking any measurements.
TISAB IV
TISAB IV will complex more than 100 ppm of iron or aluminum
in the presence of 1 ppm fl uoride. A measurement of 1 ppm
fl uoride will be in error by 5% in the presence of 200 ppm iron
or aluminum.
To prepare TISAB IV: Place 500 mL of distilled water in a 1 liter
volumetric fl ask. Add 84 mL of concentrated HCl (36 to 38 %),
242 g TRIS (hydroxymethyl) aminomethane and 230 g sodium
tartrate (Na
2
C
4
H
4
0
6
-2H
2
O) to the fl ask. Stir to dissolve the solids
and cool the solution to room temperature. Dilute to the fl ask
mark with distilled water.
Use as directed for TISAB II; combine equal volumes of TISAB IV
and sample or standard before measurements.
