Working with Ion-Selective Electrodes Chemical Laboratory Practice

The first section introduces the electrochemical nomenclature necessary for under­ standing the literature on ion-selective electrodes and discusses the general principles behind all electrodes. The second section is concerned with the problems which arise in any accurate elec­ trode potential measurement in practice. Here the most important reference electrodes are discussed with special reference to their use in conjunction with ion-selective elec­ trodes. From experience, almost 75% of all problems which arise when working with ion-selective electrodes are on account of the reference electrode. After the reader is aquainted with the basic problems involved, the third section deals with individual ion-selective electrodes; their properties, handling and methods of pre­ paration. Here the discussion of these electrodes is not arranged according to the spe­ cies detected, but rather according to the kind of construction, since from this view­ point characteristic properties are much the same and handling procedures need only be described once for an entire series of similar electrodes. The fourth section discusses amplifiers. Here the problems of high-ohmic EMF meas­ urements such as noise level, insulation, static charging and ground loops are discussed. The fifth section is devoted to the various evaluation methods. Here a few schemes and examples are provided to indicate optimum practical procedures and the accura­ cies attainable with the various methods are discussed. The last section describes special set-ups such as clinical flow-thru cells, microelec­ trodes for measuring intracellular ionic activities, industrial on-line techniques and continuous environmental protection monitors.

1 Fundamentals of Potentiometry.- 1.1 Electrode Processes.- 1.2 The Nernst Equation.- 1.3 Potential-Determining Ions.- 1.4 Ion-Selective Electrode Materials.- 1.5 The Potentiometric Selectivity Coefficient as a Quantitative Indication of the Electrode Selectivity.- 2 Electrode Potential Measurements.- 2.1 Reference Electrodes.- 2.2 The Standard Hydrogen Electrode as a Primary Reference Electrode.- 2.3 The Liquid Junction Potential.- 2.4 Secondary Reference Electrodes.- 3 Ion-Selective Electrodes.- 3.1 General Construction Principles.- 3.2 Solid-State Membrane Electrodes.- 3.3 Porous and Nonporous Supported Ion Exchanger and Neutral Carrier Membrane Electrodes.- 3.4 Solid State Electrodes with Electroactive Coatings.- 3.5 Gas Sensors For CO2, NH3, SO2, NO2, HF, H2S, HCN, etc..- 3.6 Bio-Sensors.- 4 Measuring Techniques with Ion-Selective Electrodes.- 4.1 Equivalent Circuit for a Cell with Liquid Junction.- 4.2 Measuring the EMF of an Electrochemical Cell.- 4.3 Choosing an EMF Measuring Device.- 4.4 Characteristics of Electrometer Amplifiers.- 5 Analysis Techniques Using Ion-Selective Electrodes.- 5.1 Calibration Curves.- 5.2 Direct Indication on the pH or plon Scale of an Instrument.- 5.3 Titration Procedures for Determining Concentrations.- 5.4 Concentration Determinations with the Help of a Standard Addition with a Known Electrode Slope S.- 5.5 Concentration Determinations with the Help of a Standard Addition with an Unknown Electrode Slope S.- 5.6 Practical Example of the Addition Method: Sodium and Potassium Determination in Blood Serum.- 5.7 Concentration Determinations with the Help of a “Mathematically Linearized” Titration Curve.- 5.8 Practical Example of the Gran Extrapolation Method: Determination of Chloride in the ppm Range.- 5.9. Determination of SomeCharacteristic Electrode Parameters.- 6 Applications of Ion-Selective Electrodes.- 6.1 Physiology, Biology, Medicine.- 6.2 Continuous Measurements in Industry and Environmental Research.- Outlook.- A.1 Concentration, Activity and Activity Coefficient.- A.1.1 Preparing Accurate Activity Calibration Solutions.- A.2 Survey of the Temperature Dependence of Commonly Used Reference Electrodes.- A.3 Table for Evaluation Using Analysis Technique 5.4.1.- A.4 Table for Evaluation Using Analysis Technique 5.4.2.- A.5 Table for Evaluation Using Analysis Technique 5.5.1.- A.6 Table for Evaluation Using Analysis Technique 5.5.2.- A.7 Evaluation Table for Standard Addition + 1:1 Dilution.- A.8 Ion-Selective Electrode Manufacturers and/or Dealers.- Literature.- Index of Symbols Used.