Thermo Scientific ISE User manual

User Guide

Fluoride Ion

Selective

Electrode

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trademarks of Thermo Fisher Scientiﬁc, Inc. and its subsidiaries.

Guaranteed Success and The Technical Edge are service marks of

Thermo Fisher Scientiﬁc, Inc. and its subsidiaries.

trademarks are the property of Thermo Fisher Scientiﬁc, Inc. and

its subsidiaries.

The speciﬁcations, descriptions, drawings, ordering information

and part numbers within this document are subject to change

without notice.

This publication supersedes all previous publications on this

subject.

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 978.232.6031. 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.

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