Electroanalytical Chemistry: Principles, Best Practices, and Case Studies

Provides a strong foundation in electrochemical principles and best practices Written for undergraduate majors in chemistry and chemical engineering, this book teaches the basic principles of electroanalytical chemistry and illustrates best practices through the use of case studies of organic reactions and catalysis using voltammetric methods and of the measurement of clinical and environmental analytes by potentiometric techniques. It provides insight beyond the field of analysis as students address problems arising in many areas of science and technology. The book also emphasizes electrochemical phenomena and conceptual models to help readers understand the influence of experimental conditions and the interpretation of results for common potentiometric and voltammetric methods. Electroanalytical Chemistry: Principles, Best Practices, and Case Studies begins by introducing some basic concepts in electrical phenomena. It then moves on to a chapter that examines the potentiometry of oxidation-reduction processes, followed by another on the potentiometry of ion selective electrodes. Other sections look at: applications of ion selective electrodes; controlled potential methods; case studies in controlled potential methods; and instrumentation. The book also features several appendixes covering: Ionic Strength, Activity and Activity Coefficients; The Nicolsky-Eisenman Equation; The Henderson Equation for Liquid Junction Potentials; Selected Standard Electrode Potentials; and The Nernst Equation Derivation. Introduces the principles of modern electrochemical sensors and instrumental chemical analysis using potentiometric and voltammetric methods Develops conceptual models underlying electrochemical phenomena and useful equations Illustrates best practice with short case studies of organic reaction mechanisms using voltammetry and quantitative analysis with ion selective electrodes Offers instructors the opportunity to select focus areas and tailor the book to their course by providing a collection of shorter texts, each dedicated to a single field Intended as one of a series of modules for teaching undergraduate courses in instrumental chemical analysis Electroanalytical Chemistry: Principles, Best Practices, and Case Studies is an ideal textbook for undergraduate majors in chemistry and chemical engineering taking instrumental analysis courses. It would also benefit professional chemists who need an introduction to potentiometry or voltammetry.

Table of Contents:
Preface ix 1. Basic Electrical Principles 1 1.1 Overview 2 1.2 Basic Concepts 4 1.2.1 Volt Defined 7 1.2.2 Current Defined 7 1.2.3 Oxidation and Reduction 8 1.2.4 Current and Faraday’s Law 8 1.2.5 Potential, Work, and Gibbs’ Free Energy Change 9 1.2.6 Methods Based on Voltage Measurement Versus Current Measurement 10 1.3 Electrochemical Cells 10 1.3.1 Electrodes 10 1.3.2 Cell Resistance 12 1.3.3 Supporting Electrolyte 13 1.4 The Electrified Interface or Electrical Double Layer 14 1.4.1 Structure of the Double Layer 14 1.4.2 The Relationship Between Double Layer Charge and the Potential at the Electrode Interface 20 1.5 Conductance 22 1.6 Mass Transport by Convection and Diffusion 24 1.7 Liquid Junction Potentials 26 Problems 29 References 29 2. Potentiometry of Oxidation–Reduction Processes 31 2.1 Overview 31 2.2 Measuring “Open Circuit” Potentials 33 2.3 Solution Redox Potential 34 2.3.1 The Development of a Charge Separation 35 2.3.2 The Nernst Equation 36 2.3.3 Formal Potential 38 2.3.4 Active Metal Indicator Electrodes 41 2.3.5 Redox Titrations 52 2.3.6 Oxidation–Reduction Potential (ORP) or EH 55 2.3.7 Environmental Applications of Redox Measurements 57 Problems 64 References 66 3. Potentiometry of Ion Selective Electrodes 69 3.1 Overview 69 3.2 Liquid Membrane Devices 73 3.2.1 Selective Accumulation of Ions Inside an Organic Liquid 73 3.2.2 Theory of Membrane Potentials 77 3.2.3 Liquid Membrane Ionophores 80 3.3 Glass Membrane Sensors 82 3.3.1 History of the Development of a Glass Sensor of pH 82 3.3.2 Glass Structure and Sensor Properties 83 3.3.3 Selective Ion Exchange Model 87 3.3.4 The Combination pH Electrode 88 3.3.5 Gas-Sensing Electrodes 89 3.4 Crystalline Membrane Electrodes 93 3.5 Calibration Curves and Detection Limits 96 3.6 A Revolutionary Improvement in Detection Limits 100 3.7 More Recent Ion Selective Electrode Innovations 102 3.7.1 The Function of the Inner Reference Electrode 103 3.7.2 All Solid-State Reference Electrodes 104 3.7.3 Eliminating the Inner Reference Electrode 105 3.7.4 Super-Hydrophobic Membranes 107 3.8 Ion Selective Field Effect Transistors (ISFETs) 108 3.9 Practical Considerations 111 3.9.1 Ionic Strength Buffers 111 3.9.2 Potential Drift 112 Problems 112 References 114 4. Applications of Ion Selective Electrodes 117 4.1 Overview 117 4.2 Case I. An Industrial Application 118 4.2.1 Will the Sample Concentrations Be Measurable? 118 4.2.2 Ionic Strength Adjustment Buffer 118 4.2.3 Sample Pretreatment 119 4.2.4 Salt Bridges 120 4.2.5 Calibration 122 4.2.6 Temperature Control 123 4.2.7 Signal Drift 124 4.2.8 Validating the Method 124 4.2.9 Standard Additions for Potentiometric Analysis 127 4.3 Case II. A Clinical Application 130 4.4 Case III. Environmental Applications 135 4.4.1 US EPA Method for Nitrate Determination by ISE 136 4.4.2 Field Measurements 139 4.5 Good Lab Practice for pH Electrode Use 142 4.5.1 Electrode Maintenance 142 4.5.2 Standard Buffers 143 4.5.3 Influence of Temperature on Cell Potentials 143 4.5.4 Calibration and Direct Sample Measurement 145 4.5.5 Evaluating the Response of a pH Electrode 145 4.5.6 Calibrating a Combination Electrode and pH Meter 147 4.5.7 Low Ionic Strength Samples 148 4.5.8 Samples Containing Soil, Food, Protein or Tris Buffer 148 4.5.9 pH Titrations 149 4.5.10 Gran Plots 149 Problems 151 References 153 5. Controlled Potential Methods 157 5.1 Overview 157 5.2 Similarities between Spectroscopy and Voltammetry 161 5.3 Current is a Measure of the Rate of the Overall Electrode Process 163 5.3.1 Rate of Electron Transfer 163 5.3.2 The Shape of the Current/Voltage Curve 167 5.3.3 Rate of Mass Transport 168 5.3.4 Electrochemical Reversibility 173 5.3.5 Voltammetry at Stationary Electrodes in Quiet Solutions 175 5.4 Methods for Avoiding Background Current 186 5.5 Working Electrodes 190 5.5.1 Mercury Electrodes 190 5.5.2 Solid Working Electrodes 191 5.5.3 Ultramicroelectrodes 199 5.5.4 Fast Scan CV 204 5.6 Pulse Amperometric Detection 207 5.7 Stripping Voltammetry 209 5.8 Special Applications of Amperometry 212 5.8.1 Flow-Through Detectors 212 5.8.2 Dissolved Oxygen Sensors 213 5.8.3 Enzyme Electrodes 215 5.8.4 Karl Fisher Method for Moisture Determination 218 5.9 Ion Transfer Voltammetry 222 Problems 230 References 235 6. Case Studies in Controlled Potential Methods 237 6.1 Overview 237 6.2 Case I. Evaluating the Formal Potential and Related Parameters 238 6.3 Case II. Evaluating Catalysts – Thermodynamic Considerations 242 6.4 Case III. Studying the Oxidation of Organic Molecules 246 6.5 Case IV. Evaluating Catalysts – Kinetic Studies 260 References 268 7. Instrumentation 269 7.1 Overview 269 7.2 A Brief Review of Passive Circuits 270 7.3 Operational Amplifiers 273 7.3.1 Properties of an Ideal Operational Amplifier 275 7.3.2 The Voltage Follower 275 7.3.3 Current Follower or Current-to-Voltage Converter 276 7.3.4 Inverter or Simple Gain Amplifier 277 7.3.5 A Potentiostat for a Three-Electrode Experiment 279 7.4 Noise and Shielding 280 7.5 Making Electrodes and Reference Bridges 283 7.5.1 Voltammetric Working Electrodes 283 7.5.2 Reference Electrodes 284 Problems 286 References 288 Appendix A Ionic Strength, Activity, and Activity Coefficients 289 Appendix B The Nicolsky–Eisenman Equation 293 Appendix C The Henderson Equation for Liquid Junction Potentials 297 Appendix D Standard Electrode Potentials for Some Selected Reduction Reactions 303 Appendix E The Nernst Equation from the Concept of Electrochemical Potential 307 Solutions to Problems 311 Index 333