Thermo Scientific ISE User manual

User Guide
Fluoride Ion
Selective
Electrode

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Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Required Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Electrode Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Electrode Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Checking Electrode Operation (Slope) . . . . . . . . . . . . . . . . . . . . .6
Measurement Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Sample Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Measuring Hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Electrode Storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Electrode Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Analytical Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Direct Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Low-Level Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Single Known Addition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Titrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
Fluoride in Acid Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Fluoride in Alkaline Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Electrode Characteristics . . . . . . . . . . . . . . . . . . . . . . . . .33
Electrode Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Reproducibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Limits of Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Temperature Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Interferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
pH Effects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Complexation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36
Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
Assistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Troubleshooting Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

1Fluoride Ion Selective Electrode User Guide
Introduction
This user guide contains information on the preparation,
operation and maintenance for the fluoride ion selective
electrode (ISE). General analytical procedures, electrode
characteristics and electrode theory are also included in this
user guide. Fluoride electrodes measure free fluoride ions in
aqueous solutions quickly, simply, accurately and economically.
The measurement of fluoride in drinking water and wastewater
using an ion selective electrode is an EPA approved test
procedure. EPA-approved ISE test procedures for fluoride in
drinking water are ASTM D1179-04 (B) and Standard Methods
4500-F- C (21st edition). EPA-approved ISE test procedures for
fluoride in wastewater are ASTM D1179-93, 99 (B) and Standard
Methods 4500-F- C-97 (online) or 4500-F- B (18, 19, 20th
editions). Approved test method lists are updated periodically.
Check with your regulatory agency for latest approve method
revisions.
Technical Support Chemists can be consulted for assistance
and troubleshooting advice. Within the United States call
1.800.225.1480 and outside the United States call 978.232.6000
or fax [phone]. In Europe, the Middle East and Africa,
contact your local authorized dealer. For the most current
contact information, visit www.thermoscientific.com/water.
Fluoride ionplus®Sure-Flow®Solid State Combination ISE
The reference and sensing electrodes are built into one
electrode, which decreases the amount of required solution
and reduces waste. The built-in Sure-Flow reference junction
prevents electrode clogging and provides fast and stabile
readings. The fluoride ionplus combination ISE is available with
a waterproof BNC connector, Cat. No. 9609BNWP. Electrodes
with a waterproof BNC connector can be used on any ISE meter
with a BNC connection.
Fluoride Solid State Half-Cell ISE
The fluoride half-cell electrode must be used with the single
junction reference electrode, Cat. No. 900100. The fluoride
half-cell is available with a BNC connector, Cat. No. 9409BN;
and a screw cap connector, Cat. No. 9409SC. Electrodes with a
screw cap connector require a separate cable.

2Fluoride Ion Selective Electrode User Guide
cap
cable
spring
O-ring
filling hole
inner cone
sensing crystal
reference
element
filling solution
chamber
outer body
inner
body
Figure 1
9609BNWP Fluoride Combination Electrode

3Fluoride Ion Selective Electrode User Guide
Required Equipment
1. Thermo Scientific Orion ISE meter, such as the Orion 4-Star
pH/ISE meter, Orion 5-Star pH/ISE/DO/conductivity meter
or Orion DUAL STAR meter.
Fluoride electrodes can be used on any ISE meter with
a BNC connection. The electrodes can also be used on
meters with a variety of inputs when an adapter cable is
used. Visit www.thermoscientific.com/water for details.
2. Thermo Scientific Orion fluoride ion selective electrode.
The 9409BN and 9409SC fluoride half-cell electrodes
require a separate reference electrode,
Cat. No. 900100.
3. Magnetic stirrer or Orion stirrer probe, Cat. No. 096019.
The Orion stirrer probe can be used with 3-Star, 4-Star, 5-
Star benchtop meters, and Dual Star meter.
4. Volumetric flasks, graduated cylinders and beakers.
Plastic labware is highly recommended for fluoride analysis.
5. Distilled or deionized water.
6. Fluoride electrode filling solution.
Use Optimum Results A filling solution, Cat. No. 900061,
for the 9609BNWP fluoride electrodes.
Use single junction reference electrode filling solution,
Cat. No. 900001, for the reference electrode used with the
9409BN and 9409SC fluoride electrodes.
7. Fluoride calibration standards.
Cat. No. Description
940906 0.1 M NaF, 475 mL bottle
940907 100 ppm F¯, 475 mL bottle
040908 10 ppm F¯ with TISAB II, 475 mL bottle
040907 2 ppm F¯ with TISAB II, 475 mL bottle
040906 1 ppm F¯ with TISAB II, 475 mL bottle

4Fluoride Ion Selective Electrode User Guide
8. Total Ionic Strength Adjustment Buffer (TISAB),
which provides a constant background ionic strength,
decomplexes fluoride 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) fluoride and no fluoride 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 flask and dilute to the
flask mark with distilled water. All reagents must be as pure as
possible to keep the fluoride 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 fluoride. A measurement of 1 ppm
fluoride 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 flask. Add 84 mL of concentrated HCl (36 to 38 %),
242 g TRIS (hydroxymethyl) aminomethane and 230 g sodium
tartrate (Na2C4H406-2H2O) to the flask. Stir to dissolve the solids
and cool the solution to room temperature. Dilute to the flask
mark with distilled water.
Use as directed for TISAB II; combine equal volumes of TISAB IV
and sample or standard before measurements.

5Fluoride Ion Selective Electrode User Guide
Electrode Setup
Electrode Preparation
9409BN and 9409SC Fluoride Half-Cell Electrode– Remove the
protective shipping cap from the sensing element and save the
cap for storage.
900100 Single Junction Reference Electrode– Prepare the
reference electrode according to the reference electrode user
guide. Fill the reference electrode with single junction reference
filling solution, Cat. No. 900001.
9609BNWP Fluoride Combination Electrode– Remove the
protective shipping cap from the sensing element and save
the cap for storage. Fill the electrode with Optimum Results A
filling solution, Cat. No. 900061.
Note: Optimum Results A filling solution minimizes junction
potential issues and fluoride contamination in the sample. The
use of any other filling solution will void the electrode warranty.
Electrode Filling Instructions
1. Lift the flip spout on the filling solution bottle to a vertical
position.
2. Insert the spout into the filling hole on the outer body of the
electrode and add a small amount of filling solution to the
reference chamber. Invert the electrode to moisten the top
O-ring and then return the electrode to the upright position.
3. Hold the electrode body with one hand and use your thumb
to push down on the electrode cap to allow a few drops of
filling solution to drain out of the electrode.
4. Release the electrode cap. If the sleeve does not return to
its original position, check if the O-ring is moist and repeat
steps 2-4 until the sleeve returns to the original position.
5. Add filling solution to the electrode up to the filling hole.
Note: Add filling solution each day before using the electrode.
The filling solution level should be at least one inch above the
level of sample in the beaker to ensure a proper flow rate. The
fill hole should always be open when taking measurements.

6Fluoride Ion Selective Electrode User Guide
Checking Electrode Operation (Slope)
These are general instructions that can be used with most
meters to check the electrode operation. Refer to the meter
user guide for more specific information.
This procedure measures electrode slope. Slope is defined
as the change in millivolts observed with every tenfold change
in concentration. Obtaining the slope value provides the best
means for checking electrode operation.
1. If the electrode has been stored dry, prepare the electrode
as described in the Electrode Preparation section.
2. Connect the electrode to the meter. Set the meter to the
mV mode.
3. Place 50 mL of distilled water and 50 mL of TISAB II (Low-
level TISAB or TISAB IV) into a 150 mL beaker. Stir the
solution thoroughly.
If using TISAB III, place 90 mL of distilled water and
10 mL of TISAB III into a 150 mL beaker. Stir the solution
thoroughly.
4. Rinse the electrode with distilled water and place the
electrode into the solution prepared in step 3.
5. Select either a 0.1 M sodium fluoride or 100 ppm fluoride
standard. Pipette 1 mL of the standard into the beaker and
stir thoroughly. When a stable reading is displayed, record
the electrode potential in millivolts.
6. Pipette 10 mL of the same standard into the same beaker
and stir thoroughly. When a stable reading is displayed,
record the electrode potential in millivolts.
7. There should be a 54 to 60 mV difference between the
two millivolt readings when the solution temperature is
between 20 to 25 ˚C. If the millivolt potential is not within
this range, refer to the Troubleshooting section.