Carbon Dioxide Sensing

Scientific Biographies of the Authors xiii Scientific Biographies of the Co-Authors to Chapter 16 xvii Preface xix Part I General 1 1 Introduction 3 Wolfram Oelßner Reference 6 2 Carbon Dioxide in General 7 Detlev Möller, Manfred Decker, Jens Zosel, and Wolfram Oelßner 2.1 Chemical and Physical Properties of Carbon Dioxide 7 2.1.1 Chemical Properties of Carbon Dioxide 7 2.1.1.1 Chemical Properties 7 2.1.1.2 Industrial Use of Carbon Dioxide 8 2.1.2 Physical Properties of Carbon Dioxide 9 2.1.2.1 Mechanical Properties 9 2.1.2.2 Thermally Related Properties 10 2.1.2.3 Electrical Properties 12 2.1.2.4 Optical Properties 12 2.2 The Carbon Cycle 13 2.2.1 Sources of Carbon on Earth 13 2.2.2 Carbon Pools and Global Cycling 18 2.2.3 Carbon Budget 23 2.2.4 Subsurface CO2 Monitoring 28 2.3 Anthropogenic CO2 29 2.3.1 Biomass Burning 30 2.3.2 Land-Use Change and Deforestation 33 2.3.3 Fossil Fuel Burning 35 References 37 Part II Principles of Carbon Dioxide Sensors and Measuring Methods 45 3 Analytical Methods for the Detection of Gaseous CO2 47 Gerald Gerlach, Armin Lambrecht, and Wolfram Oelßner 3.1 Spectroscopy 47 3.1.1 Molecular Vibrations of Molecules, in Particular CO2 48 3.1.2 Characteristic Wave Numbers and Wavelengths of Gases 49 3.1.3 Absorption of Radiation in Molecules 52 3.1.4 Molecular Absorption in the Infrared Range 52 3.1.5 Line Shapes for Molecular Absorption in the Infrared Range 53 3.1.5.1 Line Broadening 54 3.1.5.2 High-Resolution Transmission Molecular Absorption Database 54 3.1.5.3 Lorentzian Line Shape 54 3.1.5.4 Gaussian Line Shape 55 3.1.5.5 Applicability of Line Shapes 55 3.1.5.6 Spectral Resolution of Individual Ro-vibrational Absorption Lines 55 3.1.6 CO2 Absorption in the Infrared Range 55 3.1.7 Laser Spectroscopy 58 3.1.7.1 Basic Measurement Concepts 60 3.1.7.2 Properties of Lasers Suitable for TLAS 61 3.1.7.3 Laser Absorption Spectroscopy Measurement Schemes 62 3.2 Gas Chromatography 67 3.2.1 Functional Principle 67 3.2.2 Classification of Chromatographic Methods 69 3.2.3 Gas Chromatography Instrumental Components 69 3.2.3.1 Autosampler 70 3.2.3.2 Sample Injection Port 70 3.2.3.3 Column 71 3.2.3.4 Carrier Gas 72 3.2.3.5 Stationary Phase 72 3.2.3.6 Detectors 75 3.2.3.7 Data Analysis 75 3.2.4 Gas Chromatography of Gaseous CO2 76 3.3 Analytical Determination of CO2 in Liquids 76 References 81 4 Electrochemical CO2 Sensors with Liquid or Pasty Electrolyte 87 Manfred Decker, Wolfram Oelßner, and Jens Zosel 4.1 Severinghaus-Type Membrane-Covered Carbon Dioxide Sensors 87 4.1.1 The Severinghaus Principle 87 4.1.1.1 Stow’s Electrode with [Na+]=0 mol l−1 92 4.1.1.2 Severinghaus Electrode with [Na+]>0.001 mol l−1 93 4.1.2 Sensor Electrolyte 95 4.1.3 Membrane Materials 96 4.1.4 Temperature Dependence 98 4.1.5 Response Behaviour 98 4.1.6 Calibration of Electrochemical CO2 Sensors 102 4.2 Coulometric and Amperometric CO2 Sensors 103 4.2.1 Operation Principle 103 4.2.2 IrO2 Electrode 105 4.2.3 Amperometric CO2 Sensors 105 4.3 Conductometric CO2 Sensors 108 4.4 Quinhydrone CO2 Electrode 110 References 111 5 Potentiometric CO2 Sensors with Solid Electrolyte 117 Hans Ulrich Guth 5.1 Indirect Measurement of CO2 in Hot Water Gas 117 5.2 Direct CO2 Measurement with Solid Electrolyte Cells 119 5.2.1 Functional Principles of Solid Electrolyte CO2 Cells 119 5.2.2 General Setup 123 5.2.2.1 Pellet Sensors 123 5.2.2.2 Thick-Film Sensors 123 5.3 Solid-State Sensors Based on Changes in Capacity and Resistivity 129 References 130 6 Opto-Chemical CO2 Sensors 133 Gerald Gerlach and Wolfram Oelßner 6.1 Liquid Reagent-Based Opto-Chemical CO2 Sensors 133 6.2 CO2 Detector Tubes 136 6.3 Fibre-Optic Fluorescence CO2 Sensors 141 6.3.1 Fibre-Optic Sensors 141 6.3.1.1 Light Propagation in Optic Fibres 141 6.3.1.2 General Set-Up and Basic Components 142 6.3.1.3 Optical Fibres 142 6.3.1.4 Interaction Between Light and External Measurand 144 6.3.1.5 Advantages of Fibre-Optic Sensors 146 6.3.2 Fibre-Optic Fluorescence Gas Sensors 146 6.3.2.1 General 146 6.3.2.2 Fluorescent Sensor Dyes for CO2 Detection 146 6.3.2.3 Fibre-Optic CO2 Sensors 148 6.3.2.4 Commercial Fibre-Optic CO2 Sensor Solutions 150 References 152 7 Non-dispersive Infrared Sensors 157 Gerald Gerlach 7.1 Basic Principle and General Set-Up 157 7.1.1 General Set-Up 157 7.1.2 Gas Selectivity 159 7.2 NDIR Components 159 7.2.1 Infrared Detectors 159 7.2.1.1 Pyroelectric IR Sensors 160 7.2.1.2 Thermopiles 164 7.2.1.3 Comparison of Detectors 165 7.2.2 Wavelength Selection by IR Filters 167 7.2.2.1 IR Filters 167 7.2.2.2 Fabry–Pérot Filters 168 7.2.3 IR Radiation Sources 171 7.2.3.1 Requirements 171 7.2.3.2 IR Radiation Source Selection 171 7.2.3.3 Thermal Emitters 173 7.2.4 Gas Sensors for Measuring CO2 in Gas Mixtures 174 7.3 NDIR Sensors 175 7.3.1 Commercial NDIR Sensors 175 7.3.2 Application for Very Small Concentrations and for Liquid Samples 177 7.3.2.1 Pre-Concentrators for Low Gas Concentrations 177 7.3.2.2 Measurement of Dissolved CO2 in Liquids by Using Permeation Methods 177 7.4 IR Spectrometers 178 7.4.1 Types of IR Spectrometers 178 7.4.2 Applications 181 7.5 IR Imaging for CO2 Detection 182 References 184 8 Photoacoustic Detection of CO2 191 Frank Kühnemann 8.1 Photoacoustic Effect and Photoacoustic Gas Detection 191 8.1.1 Photoacoustic Cell as Gas-Specific Radiation Detector 192 8.1.2 Photoacoustic Detection in the Sample Cell 193 8.2 Photoacoustic Signal Generation 194 8.3 Photoacoustic Gas Analysis with Thermal Sources 197 8.3.1 Photoacoustic Cell as Gas-Specific Radiation Detector 197 8.3.2 Miniaturized PA Detection Systems 199 8.3.3 Photoacoustic Detection in the Gas Sample 200 8.4 Laser-Based Photoacoustic Trace Gas Detection 202 8.4.1 General Overview 202 8.4.2 Resonant Photoacoustic Cell Design 203 8.4.3 Acoustic Detectors 204 8.4.3.1 Quartz-Enhanced Photoacoustic Spectroscopy 205 8.4.3.2 Cantilever-Enhanced Laser-PAS 208 8.4.4 Detection Limits of CO2 Gas Analysis with Laser-Based PAS 209 References 210 9 Acoustic CO2 Sensors 215 Gerald Gerlach 9.1 Basic Principles of Resonant Sensors 216 9.1.1 General Set-Up 216 9.1.2 Piezoelectric Resonators 218 9.1.2.1 Circuit Model 218 9.1.2.2 Resonance Frequencies 220 9.1.2.3 Types of Piezoelectric Resonant Sensors 221 9.2 Quartz Crystal Microbalance Sensors 222 9.2.1 Quartz as Resonator Material 222 9.2.2 Thickness Shear Mode Sensors 223 9.2.2.1 Vibration Modes 223 9.2.2.2 Sensitivity 225 9.2.2.3 Commercial QCM Sensors 226 9.2.3 CO2-Sensitive Coating 226 9.2.4 Other Applications of CO2-Sensitive QCMs 226 9.3 Surface Acoustic Wave Sensors 228 9.3.1 Operation Principle 228 9.3.1.1 Excitation of Surface Acoustic Waves 228 9.3.1.2 Operation Modes of SAW Sensors 229 9.3.2 SAW Sensor Materials 231 9.3.3 SAW Devices 232 9.3.4 CO2-Sensitive SAW Sensors 235 9.4 Ultrasonic CO2 Sensors 235 9.4.1 Operation Principle 235 9.4.1.1 Velocity of Sound in Gases 235 9.4.1.2 Basic Set-Up 239 9.4.2 Ultrasonic Sensors for CO2 Detection 240 References 241 10 Miscellaneous Approaches 247 Wolfram Oelßner, Manfred Decker, and Gerald Gerlach 10.1 Hydrogel-Based CO2 Sensors with Pressure Transducer 247 10.2 Miniaturized and ISFET-Based CO2 Sensors 250 10.3 Thermal Conductivity CO2 Detectors 253 10.4 Membrane-Based CO2 Sensors with Pressure Measurement 256 References 258 11 Survey and Comparison of Methods 263 Hans Ulrich Guth, Gerald Gerlach, and Wolfram Oelßner Part III Applications 273 12 Environmental CO2 Monitoring 275 Detlev Möller and Wolfram Oelßner 12.1 CO2 and Climate Change 275 12.1.1 The Carbon Dioxide Environmental Problem 275 12.1.2 Rise of Atmospheric CO2 276 12.2 Atmospheric CO2 279 12.2.1 Pre-industrial CO2 Level 279 12.2.2 Pre-industrial CO2 Level Derived from Ice Core Data 283 12.2.3 CO2 Increase in the Twentieth Century 286 12.2.3.1 Mauna Loa CO2 Record 286 12.2.3.2 Latitudinal Variation 289 12.2.3.3 Timely Variations 290 12.2.3.4 The City Dome CO2 291 12.2.4 Atmospheric CO2 Residence Time 292 12.2.5 Atmospheric CO2 Chemistry 294 12.3 Oceanic and Water CO2 and Carbonate Content 297 12.3.1 CO2 Water Chemistry 297 12.3.2 Total Dissolved Carbon (DIC) 301 12.3.3 Changing Seawater Carbonate 303 12.3.4 Oceanic CO2 Measurements 307 12.3.5 CO2 Measurements in Waters and Boreholes 312 References 317 13 CO2 Safety Control 329 Wolfram Oelßner 13.1 Limit Values for CO2 Concentrations at Workplaces 329 13.2 CO2 in Buildings and Workplaces 330 13.2.1 Air Quality with Respect to CO2 330 13.2.2 Sick-Building Syndrome 332 13.2.3 Dangerous Areas 334 13.3 CO2 Warning Devices 336 13.3.1 CO2 Detector and Dosimeter Tubes 336 13.3.2 Electrochemical CO2 Sensors 337 13.3.3 NDIR CO2 Sensors 338 13.3.3.1 Properties 338 13.3.3.2 Calibration of NDIR CO2 Measuring Devices 341 13.3.3.3 Pressure Dependence 341 13.3.3.4 Response Time 342 13.3.4 Solid Electrolyte CO2 Sensors 342 13.3.5 Gas Chromatograph with Thermal Conductivity Detector 343 References 343 14 CO2 Measurement in Biotechnology and Industrial Processes 349 Wolfram Oelßner and Jens Zosel 14.1 Beverage and Food Industry 349 14.1.1 Sensor Principles 350 14.1.1.1 Electrochemical Sensors 350 14.1.1.2 p/T (Pressure/Temperature) Sensors 350 14.1.1.3 NIR-Based In-Line CO2 Measurement 351 14.1.1.4 Thermal Conductivity Sensors 351 14.1.1.5 Other Sensor Principles 351 14.1.2 Application Examples 352 14.2 Bioreactors 356 14.3 Biogas Plants 359 References 362 15 CO2 Measurements in Biology 367 Wolfram Oelßner 15.1 Aquatic Animals 367 15.1.1 Fish 367 15.1.1.1 Influence of CO2 Concentration on Fish 367 15.1.1.2 Methods to Determine CO2 Concentrations 368 15.1.1.3 Behaviour of Fish in Regions with Increased CO2 Concentration 369 15.1.2 Mussels 372 15.1.2.1 Respiratory Quotient 372 15.1.2.2 Respiratory Exchange 373 15.2 Insects 376 15.2.1 CO2 Measurements on Butterfly Pupae 376 15.2.2 CO2 Measurements on Honeybees 379 15.3 Plants 381 References 385 16 CO2 Sensing in Medicine 391 Gerald Urban, Josef Guttmann, Jochen Kieninger, AndreasWeltin, Jürgen Wöllenstein, and Jens Zosel 16.1 Introduction 391 16.2 Physiological Background of CO2 Sensing 392 16.3 Measuring Principles 393 16.3.1 Electrochemical Principle: Severinghaus Method 393 16.3.2 Optical Principles 394 16.3.3 New and Unconventional CO2 Measuring Principles 395 16.4 Clinical Applications 395 16.4.1 Blood Gas Analysing Devices 395 16.4.2 Monitoring Devices 396 16.4.2.1 Transcutaneous pCO2 Measurement (tcpCO2) 396 16.4.2.2 Blood Monitoring Devices: Direct Venous or Arterial Monitoring of Blood Gases 398 16.5 Comparison of Methods and Conclusions 399 16.6 CO2 Analysis in Human Breath 399 16.6.1 Methods for CO2 Detection in Breath 400 16.6.1.1 Qualitative and Semi-Quantitative Detection 400 16.6.1.2 Quantitative Detection by Non-Dispersive Infrared Absorption 401 16.7 CO2 Measurements on Baby Mattresses 405 References 408 Index 415