A Beginners Guide
to Ion-Selective Electrode
Measurements

Chris C Rundle BSc, PhD. (Nico2000 Ltd, London, UK.)
Biography of author

First Public Version 05/05/2000
Major revision, including introduction of internet links, diagrams and illustrations: June 2004
Last Update: 5 June 2008 (Chapter 6)
Please Email chris.rundle@nico2000.net with any comments or suggestions for improvement.

CONTENTS

1)    FOREWORD, RATIONALE AND ACKNOWLEDGEMENTS

2)    INTRODUCTION TO ION SELECTIVE ELECTRODES
         a) Applications.
         b) Advantages

3)    BASIC THEORY OF ISE MEASUREMENTS.
         a) The pH Electrode.
         b) Differences Between pH and Other Ion-Selective Electrodes.

4)    TYPES OF ION SELECTIVE ELECTRODES
         a) General Discussion.
         b) Crystal-Membrane Electrodes: e.g. Fluoride.
         c) Impregnated-PVC-Membrane Electrodes: e.g. Potassium.
         d) Care and Maintenance of ISEs.

5)    REFERENCE ELECTRODES
         a) The Silver / Silver Chloride Single Junction Reference Electrode.
         b) Double Junction Reference Electrodes.
         c) Liquid Junction Potentials.
         d) Combination Electrodes.
         e) Multiple Electrode Heads: Separable Combinations.

6)    PROBLEMS WITH ISE MEASUREMENTS
         a) Ionic Interference and Selectivity Coefficients.
         b) Ionic Strength and Activity Coefficients: Activity versus Concentration.
         c) Ionic Strength Adjustment Buffers.
         d) Potential Drift.

7)    CALIBRATION THEORY
         a) Linear Range.
         b) Total Measuring Range.
         c) Limit of Detection.

8)    CALIBRATION PRACTICE
         a) Standard Solutions.
         b) Minimising Drift Effects During Calibration.
         c) Frequency of Calibration.

9)    MEASURING PROCEDURES
         a) Adding ISAB.
         b) Taking Readings and Minimising Drift Effects.
         c) Cleaning Electrodes and Minimising Hysteresis Between Samples.

10)    METHODS OF ANALYSIS
         a) Direct Potentiometry.
         b) Incremental Methods: Standard Addition, Sample Addition & Subtraction.
         c) Potentiometric Titrations.

11)    ACCURACY AND PRECISION OF SAMPLE MEASUREMENTS.
          a) General Discussion.
          b) Reproducibility Experiments Using an Ammonium Electrode.
          c) Reproducibility of Chloride Measurements.
          d) Standard Addition & Sample Addition Methods.
          e) Conclusions from Experimental Data.

12)    TYPES OF MEASURING DEVICES AND DATA PROCESSING
         a) Analogue Meters.
         b) Digital Meters.
         c) Self-Calibrating, Direct-Reading Ion Meters.

13)    RECENT DEVELOPMENTS
         a) Meterless Computer Interfaces.
         b) Data Processing Software.
         c) Multi-Component Analysis.

14)    RECENT RESEARCH INTO CORRECTIONS FOR INTERFERING IONS
         a) Rationale and Problems.
         b) Creating a Calibration Net.
         c) Interfering Ion Correction Software.

15)    LOOKING TO THE FUTURE.

APPENDICES - Available at www.nico2000.net.

A)    GLOSSARY OF TERMS AND CALCULATIONS

B)   INTERNET LINKS & BIBLIOGRAPHY
        Including over 100 links to Research Papers and Articles about
        Ion-Selective Electrode theory and practice available on the WWW.

C)    OPERATING INSTRUCTIONS FOR ELIT ION-SELECTIVE ELECTRODES
        Includes all the latest updates

D)   CATALOGUE OF NICO2000 ELECTROCHEMICAL PRODUCTS
         MS Word 97 document (4*A4 pages)

E)   MS "POWER POINT" PRESENTATION
        About ELIT Ion Analyser Systems.

F)    DEMONSTRATION SOFTWARE FOR ELIT ION ANALYSERS
        Download or request a free CD

Go To Chapter 1