Fluoride Ion-Selective Electrodes

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Table of Contents

Introduction………………………………………………………………………………. 2

Procedure………………………………………………………………………………… 4

Data………………………………………………………………………………………. 7

Results and Discussion…………………………………………………………………... 9

Conclusion and Opinion………………………………………………………………... 10

References……………………………………………………………………………..... 11

Introduction

Purpose

The purpose of this experiment is to determine the weight percent of fluoride in a toothpaste sample by using a fluoride ion-selective electrode. Using the fluoride ion-selective electrode will offer an introduction to the procedures of potentiometric analysis [2].

By comparing the experimentally determined weight percent of fluoride to the known value listed by the toothpaste manufacturer, the accuracy of this experiment can be assessed. It is important to accurately measure fluoride levels in consumer products because fluoride can be lethal. While small a small amount of fluoride is necessary for healthy bones and teeth, too much fluoride can cause kidney failure and death [2].

Potentiometry

Potentiometric analysis measures potential with a voltmeter, reference electrode, and indicator electrode. There is no net current with these measurements [1].

Fluoride Ion-Selective Electrode

A fluoride ion-selective electrode, or FISE, is a type of indicator electrode. This solid-state type electrode has an ion-selective membrane made of LaF3. The FISE is filled with a solution that contains F- ions. The concentration of this filling solution is higher than that of the sample solution, so F- ions leave the electrode, pass through the membrane, and enter the sample solution. The free energy from this diffusion of F- ions creates the potential that is measured by the voltmeter [1-3]....

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... use to determine the amount of NaCl to add to each solution. This part was difficult because instructions were not very clear. Consequently, a member of my group used incorrect volumes in her equations and added incorrect amounts of NaCl. Because of this, we had to use another lab group’s data.

Improvements

Detailed instructions on the use of the pipette would make

this lab easier. Additionally, an explanation of the ionic strength equation and the determination of NaCl additions would be helpful.

References

1. Barlag, Becky. Class Notes 2013.

2. Barlag, Becky. Lab Manual for Analytical Chemistry I, Fluoride Ion-Selective

Electrodes. Ohio University, 2013.

3. Ion-Selective Electrode: The Measurement of Fluoride Ion Activity in Mouthwash,

Toothpaste, and Drinking Water. University of Conneticut, 1999. http://chemweb.chem.uconn.edu.

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