Working with Ion-Selective Electrodes

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.- 2.2.1 Preparation.- 2.2.2 Characteristics.- 2.3 The Liquid Junction Potential.- 2.3.1 Origin.- 2.3.2 Calculation.- 2.3.3 Salt Bridge Electrolytes.- 2.3.4 Construction of the Salt Bridge Electrolyte/Sample Solution Contact Zone.- 2.3.5 Cells Without Liquid Junction.- 2.4 Secondary Reference Electrodes.- 2.4.1 Silver/Silver Chloride.- 2.4.1.1 Preparation.- 2.4.1.2 Characteristics.- 2.4.2 Thallium Amalgam/Thallium (I) Chloride (Thalamid®).- 2.4.2.1 Characteristics.- 2.4.3 Mercury/Mercury (I) Chloride (Calomel).- 3 Ion-Selective Electrodes.- 3.1 General Construction Principles.- 3.2 Solid-State Membrane Electrodes.- 3.2.1 Glass Membrane Electrodes For Li+, Na+, K+, Rb+, Cs+, NH4+, NR4+, Ag+, Tl+ Ions.- 3.2.1.1 Construction.- 3.2.1.2 Characteristics.- 3.2.1.3 Handling.- 3.2.1.4 Sample Preparation.- 3.2.2 Homogeneous Solid-State Membrane Electrodes For Ag+, Cd2+, Cu2+, Pb2+, S2-, F-, Cl-, Br-, I-, SCN-, CN- Ions.- 3.2.2.1 Principles.- 3.2.2.2 Construction.- 3.2.2.3 Preparation of Solid-State Membrane Electrodes Based on Ag2S.- 3.2.2.4 Characteristics.- 3.2.2.5 Handling.- 3.2.2.6 Sample Preparation.- 3.2.3 Heterogeneous Solid-State Membrane Electrodes For Ag+, Cl-, Br-, I-,CN-, SCN-, S2- Ions.- 3.2.3.1 Construction.- 3.2.3.2 Preparation.- 3.2.3.3 Characteristics.- 3.2.3.4 Handling.- 3.3 Porous and Nonporous Supported Ion Exchanger and Neutral Carrier Membrane Electrodes.- 3.3.1 Ion-Exchangers For Ca2+, Me2+ Cations and Cl-, ClO4-, NO3-, BF4- Anions.- 3.3.2 Neutral Carrier Compounds For Li+, Na+, K+, Rb+, Cs+, NH4+, NR4+, Ca2+ and Ba2+ Cations.- 3.3.3 Construction.- 3.3.4 Preparation of PVC Membrane Electrodes.- 3.3.5 Characteristics.- 3.3.6 Handling.- 3.3.7 Further Electro-Active Phases.- 3.4 Solid State Electrodes with Electroactive Coatings.- 3.5 Gas Sensors For CO2, NH3, SO2, NO2, HF, H2S, HCN, etc..- 3.5.1 Principles.- 3.5.2 Construction.- 3.5.3 Characteristics of Gas-Sensitive Electrodes.- 3.5.4 Handling.- 3.5.5 Sample Preparation.- 3.6 Bio-Sensors.- 3.6.1 Principles.- 3.6.2 Construction.- 3.6.3 Preparation of Enzyme Electrodes.- 3.6.4 Characteristics of Bio-Sensors.- 3.6.5 Sample Preparation with 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.- 4.4.1 Resolving Power.- 4.4.2 Insulation Problems.- 4.4.3 Charging Phenomena.- 4.4.4 Ground Loops.- 5 Analysis Techniques Using Ion-Selective Electrodes.- 5.1 Calibration Curves.- 5.1.1 Determination of Activity Using an Activity Calibration Curve.- 5.1.2 Determination of Concentration Using a Concentration Calibration Curve.- 5.2 Direct Indication on the pH or plon Scale of an Instrument.- 5.3 Titration Procedures for Determining Concentrations.- 5.3.1 Prerequisites.- 5.3.2 Titration Errors.- 5.3.3 Sample Preparation for Titrations.- 5.3.4 Titration to a Pre-determined EMF Value.- 5.3.4.1 On the Basis of a Titration Curve.- 5.3.4.2 On the Basis of a Concentration Cell Set-Up.- 5.3.5 "Chemically Linearized" Titration Curves (One Point Titration).- 5.4 Concentration Determinations with the Help of a Standard Addition with a Known Electrode Slope S.- 5.4.1 Measuring the Change in EMF upon Addition of a Standard Solution to the Sample Solution.- 5.4.2 Measuring the Change in EMF upon Addition of the Sample Solution to a Standard Solution.- 5.5 Concentration Determinations with the Help of a Standard Addition with an Unknown Electrode Slope S.- 5.5.1 Method of Double Standard Addition.- 5.5.2 Method of Standard Addition with Subsequent Dilution.- 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.- 5.8.1 Principles.- 5.8.2 Preparatory Work.- 5.8.3 Blank Determination.- 5.8.4 Chloride Content Determination of the Sample Solution.- 5.9. Determination of Some Characteristic Electrode Parameters.- 5.9.1 Determination of the Detection Limit.- 5.9.2 Determination of the Selectivity Coefficient.- 6 Applications of Ion-Selective Electrodes.- 6.1 Physiology, Biology, Medicine.- 6.1.1 Measurements in Extracellular Fluids.- 6.1.1.1 In-vitro Measurements.- 6.1.1.1.1 Sample Preparation.- 6.1.1.1.2 The Indicating Electrode.- 6.1.1.1.3 The Reference Electrode.- 6.1.1.2 In-vivo Measurements.- 6.1.2 Measurements of Intracellular Ion Activities.- 6.1.2.1 Preparation of Ion-Selective Microelectrodes.- 6.1.2.2 Guarded Signal Wires for Extremely High Ohmic Electrodes.- 6.1.2.3 Reference Microelectrodes.- 6.1.2.4 Special Amplifiers for Microelectrode Applications.- 6.2 Continuous Measurements in Industry and Environmental Research.- 6.2.1 Flow-thru Cells.- 6.2.1.1 Influence of Grounding.- 6.2.1.2 Influence of Temperature.- 6.2.1.3 Analysis Techniques with Flow-thru Measurements.- 6.2.1.4 Flow-thru Measurements without Reference Electrodes.- 6.2.1.4.1 Direct Potentiometry.- 6.2.1.4.2 Concentration Determination through Standard Solution Addition.- 6.2.1.4.3 Indirect Concentration Determination.- 6.2.1.4.4 The Cyanide Monitor as an Example of Industrial On-Line Measurements.- 6.2.2 Concentration Determination Via a Continuous Titration.- 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.