Proton Transfer Reaction Mass Spectrometry

Proton Transfer Reaction Mass Spectrometry (PTR–MS) is a rapidly growing analytical technique for detecting and identifying very small quantities of chemical compounds in air. It has seen widespread use in atmospheric monitoring and food science and shows increasing promise in applications such as industrial process monitoring, medical science and in crime and security scenarios.   Written by leading researchers, this is the first book devoted to PTR–MS and it provides a comprehensive account of the basic principles, the experimental technique and various applications, thus making this book essential reading for researchers, technicians, postgraduate students and professionals in industry. The book contains nine chapters and is divided into two parts. The first part describes the underlying principles of the PTR–MS technique, including • the relevant ion–molecule chemistry • thermodynamics and reaction kinetics • a discussion of ion sources, drift tubes and mass spectrometers • practical aspects of PTR–MS, including calibration. The second part of the book turns its attention to some of the many applications of PTR–MS, demonstrating the scope and benefits, as well as the limitations, of the technique. The chapters that make up the second part of the book build upon the material presented in the first part and are essentially self–contained reviews focusing on the following topics: • environmental science  • food science • medicine  • homeland security, and • applications of PTR–MS in liquid analysis. INDICE: Quotation xiii Preface xv SECTION 1 FUNDAMENTALS 1 Background 3 1.1 Volatile Organic Compounds in the Earth’s Atmosphere 3 1.2 Volatile Organic Compounds in Other Environments 5 1.3 Techniques for VOC Measurements 6 1.3.1 Gas Chromatography 6 1.3.2 Ion Mobility Spectrometry 9 1.3.3 The Flowing Afterglow Technique 11 1.3.4 The Selected Ion Flow Tube 14 1.4 Emergence of Proton Transfer Reaction Mass Spectrometry 15 1.4.1 Historical Background 15 1.4.2 Compound Identification Using PTR–MS: Mass Spectrometry 17 1.4.3 An Introduction to Quantitative Aspects of PTR–MS 21 1.4.4 A Comparison between PTR–MS and SIFT–MS 22 References 23 2 Chemical Ionization: Chemistry, Thermodynamics and Kinetics 25 2.1 Introduction 25 2.2 Proton Transfer 27 2.2.1 Energy Units 27 2.2.2 Thermodynamics of Proton Transfer 27 2.2.3 Kinetics of Proton Transfer 31 2.2.3.1 Background 31 2.2.3.2 Theoretical Prediction of Proton Transfer Rate Coefficients 33 2.2.3.3 Illustrative Calculations of Proton Transfer Rate Coefficients and Comparison with Experiment 37 2.2.4 Reagents and Mechanisms 38 2.2.4.1 Chemistry of H3O+ Reactions 38 2.2.4.2 Proton Transfer from Hydrated Hydronium Clusters 42 2.2.4.3 Alternative Proton Donors 43 2.3 Other Chemical Ionization Processes 44 References 45 3 Experimental: Components and Principles 49 3.1 Introduction 49 3.2 Ion Extraction and Ion Optics 50 3.2.1 Ion Acceleration 51 3.2.2 Ion Steering 53 3.2.3 Ion Lenses 54 3.2.4 Simulation of Ion Trajectories 56 3.3 Ion Sources 57 3.3.1 Hollow Cathode Discharge Ion Source 57 3.3.2 Ion–Molecule Chemistry Leading to H3O+ Production 59 3.3.3 Alternative Ion Sources 61 3.3.4 Generating Reagent Ions Other Than H3O+ 63 3.4 Drift Tubes 64 3.4.1 Practical Aspects 64 3.4.2 Ion Mobility and Transit Times 69 3.4.3 Ion–Molecule Collision Energies 71 3.4.4 Ion Cluster Distributions 73 3.5 Mass Spectrometry 76 3.5.1 Some Important Definitions 77 3.5.1.1 Ion Mass and Mass–to–Charge Ratio 77 3.5.1.2 Mass Resolution 78 3.5.1.3 Transmission and Dynamic Range 79 3.5.2 Quadrupole Mass Spectrometry 81 3.5.2.1 Basic Principles of the Quadrupole Mass Spectrometer 81 3.5.2.2 Practical Issues 83 3.5.3 Quadrupole Ion Trap Mass Spectrometry 85 3.5.3.1 Basic Principles 85 3.5.3.2 Collision–Induced Dissociation 87 3.5.3.3 Three–Dimensional Quadrupole Ion Traps in PTR–MS 88 3.5.3.4 The Linear Ion Trap in PTR–MS 90 3.5.4 Time–of–flight Mass Spectrometry 90 3.5.4.1 Basic Principles of TOF–MS 90 3.5.4.2 Improving the Resolution: Spatial Focusing 92 3.5.4.3 Reflectron TOF–MS 94 3.5.4.4 Mass Calibration in TOF–MS 94 3.5.4.5 Advantages and Limitations of TOF–MS 95 3.5.4.6 TOF–MS Analysers in PTR–MS 96 3.6 Ion Detectors 97 3.6.1 Discrete Dynode Detector 98 3.6.2 Channel Electron Multiplier 100 3.6.3 Microchannel Plate Detector 101 3.7 Analogue versus Digital Signal Processing 103 References 106 4 Quantitative Analysis 111 4.1 Introduction 111 4.2 Extracting the Concentration of a Trace Gas from PTR–MS 111 4.3 Normalized Counts per Second 112 4.4 Why Calibrate? 113 4.5 Calibration Techniques 116 4.5.1 Static Gas Calibration 116 4.5.2 Dynamic Methods 117 4.5.3 Alternative Dynamic Calibration Procedures 119 4.6 Effect of Humidity 120 4.7 Accuracy, Precision and Limit of Detection 122 4.8 Validation of PTR–MS 125 References 126 SECTION 2 APPLICATIONS 5 PTR–MS in the Environmental Sciences 131 5.1 Background 131 5.2 Use of Reagent Ions Other Than H3O+ 138 5.3 Biogenic VOCs 141 5.3.1 General Details 141 5.3.2 Forest Emissions 142 5.3.2.1 Tropical Rainforests 142 5.3.2.2 Coniferous Forests 143 5.3.2.3 Deciduous Forests 146 5.3.2.4 Eddy Covariance Measuring Methodologies 146 5.3.2.5 Forest VOCs and m/z Assignments 150 5.3.3 Plantations 150 5.3.4 Shrubland, Grassland and Agricultural Field Emissions 151 5.3.4.1 Woodland and Grassland Savannahs 151 5.3.4.2 Shrubland 151 5.3.4.3 Alfalfa, Hay and Grass Fields 152 5.3.5 Oceans and Seas 154 5.3.5.1 Norwegian Fjord 154 5.3.5.2 Coastal Regions 155 5.3.5.3 Indian Ocean 155 5.3.5.4 Tropical Atlantic Ocean 156 5.4 Anthropogenic VOCs 156 5.4.1 Background 156 5.4.2 VOCs in Urban and Rural Sites 157 5.4.2.1 Innsbruck 157 5.4.2.2 Venezuela 158 5.4.2.3 Houston 158 5.4.2.4 Tokyo 158 5.4.2.5 Barcelona 159 5.4.2.6 Manchester and London 159 5.4.2.7 Mexico City 159 5.4.2.8 Toronto 162 5.4.2.9 Paris 162 5.4.2.10 Boston, New York and Los Angeles 163 5.4.3 Diesel Engine Emissions 163 5.4.4 Aircraft Emissions 163 5.4.5 VOC Emissions Associated with Farming 164 5.4.5.1 Cattle 164 5.4.5.2 Pigs 165 5.4.6 Other Studies of Anthropogenic VOCs 165 5.4.6.1 Air Quality 165 5.4.6.2 Firework Emissions 165 5.5 Biomass Burning 166 5.6 Applications of PTR–MS to Laboratory Studies of Atmospheric Chemistry 169 5.6.1 Laboratory Studies of Biomass Burning 170 5.6.2 Reaction Products and Reactive Species 173 5.6.3 Simulation Chamber and Container Measurements 175 5.7 Plant Studies 178 5.7.1 Isoprene Emissions 180 5.7.2 Acetaldehyde Emission Studies 183 5.7.3 Pollination 185 5.7.4 Roots and Soil 186 5.7.5 Other Plant Studies 187 5.7.5.1 Root–secreted VOCs 187 5.7.5.2 Methanol Release and Bacterial Growth: Plant–Methylobacterium Association 188 5.7.5.3 Comparison of VOC Emissions from Young and Mature Leaves 188 5.7.6 Stress–Related Emissions 189 5.7.7 VOC Emissions Linked to Plant Damage 191 5.7.7.1 Mechanical Wounding 191 5.7.7.2 Weather Damage 192 5.7.7.3 Harvesting and Mowing 193 5.7.7.4 Biofuel Crops 194 5.7.7.5 Herbivore Attack by Small Predators 195 5.7.7.6 Large Herbivore Attack 200 5.7.8 VOC Uptake by Plants 200 5.8 Outlook for Atmospheric and Environmental Applications of PTR–MS 201 References 201 6 PTR–MS in the Food Sciences 219 6.1 Background 219 6.2 Combined GC–MS and PTR–MS Studies for Food Analysis 221 6.3 Mass Spectral Fingerprinting 224 6.4 Flavour Release and Perception 225 6.4.1 Drinks 226 6.4.1.1 Coffee 226 6.4.1.2 Tea 229 6.4.1.3 Carbonated Drinks 230 6.4.1.4 Fruit Juices 231 6.4.1.5 Wine 231 6.4.1.6 Vodka 232 6.4.1.7 Infant Formula 233 6.4.2 Food 233 6.4.2.1 Cheese 233 6.4.2.2 Bread 235 6.4.2.3 Onions 235 6.4.2.4 Wheys 235 6.4.2.5 Fruit 237 6.4.3 Flavour Release: Food Texture, Composition and Physiological Effects 238 6.5 Food Classification, Food Quality and Food Control 243 6.5.1 Geographical Location 243 6.5.1.1 White Truffles 243 6.5.1.2 Butter 244 6.5.1.3 Olive Oil 245 6.5.1.4 Roe 245 6.5.1.5 Dry–Cured Ham 245 6.5.1.6 Cumin Cheese 246 6.5.2 Food Classification and Quality 247 6.5.3 Food Freshness and Ripening 248 6.5.3.1 Meat Degradation 248 6.5.3.2 Fruit and Vegetables: Ripening and Storage 249 6.5.3.3 Ripening of Cheese 251 6.5.4 Process Monitoring and Biochemical Processing 251 6.6 Outlook for Food Science and Technology Applications 254 References 255 7 PTR–MS in the Medical Sciences 265 7.1 Background 265 7.2 Breath Analysis 266 7.2.1 Smoking and Breath Volatiles 269 7.2.2 Isoprene in Breath 270 7.2.3 Acetone in Breath 273 7.2.4 Lung Studies: Cancer and Emphysema 274 7.2.5 Other PTR–MS Breath Studies 276 7.2.5.1 Crohn’s Disease and Ulcerative Colitis 276 7.2.5.2 Carbohydrate Malabsorption 276 7.2.5.3 High–Resolution PTR–TOF–MS Breath Studies 276 7.2.5.4 Kidney Function and PTR–MS 278 7.2.5.5 Liver Disease 278 7.2.6 Drug Monitoring and Pharmacokinetics Using Breath Analysis and PTR–MS 279 7.2.7 Breath VOC Levels Measured Using PTR–MS versus Blood Concentrations 282 7.2.8 Breath Sampling and PTR–MS 283 7.2.8.1 Offline Breath Sampling 284 7.2.8.2 Online Breath Sampling 285 7.2.9 PTR–MS and Breath Analysis: Requirements and Future Directions 285 7.3 Online PTR–MS Measurements of Volatile Emissions from Microbial Cultures 288 7.3.1 Bacteria 288 7.3.2 VOC Emissions from Fungi 294 7.3.3 Concluding Remarks on Microbial Emissions 295 7.4 Other Medical Applications 295 7.4.1 Urine Headspace Analysis 298 7.4.2 Skin Emissions 299 7.4.3 VOC Emissions from Human Cells 299 7.4.4 VOCs in Clinical Environments 300 References 300 8 Applications of PTR–MS to Homeland Security: The Detection of Threat Agents 309 8.1 Background 309 8.2 Explosives 310 8.2.1 Forensic Issues 310 8.2.1.1 The Unambiguous Detection of TNT 313 8.2.1.2 High Mass Resolution PTR–TOF–MS Measurements of TNT 316 8.2.1.3 Reagent Ion Switching and Explosives Detection 317 8.2.1.4 PTR–MS and the Detection of Traces of Explosives 318 8.2.2 Environmental Aspects and Explosives 318 8.3 Chemical Warfare Agents and Toxic Industrial Chemicals 319 8.4 Narcotics 320 8.5 Date Rape Drugs 323 8.6 Ion Mobility Mass Spectrometry and PTR–MS: A Brief Comparison for Homeland Security Applications 324 8.7 Future Directions 325 References 326 9 Liquid Analysis Using PTR–MS 329 9.1 Determination of Henry’s Law Constants Using PTR–MS 329 9.2 Analysis of Liquids 331 References 334 Index

• ISBN: 978-1-4051-7668-2
• Editorial: Wiley–Blackwell
• Encuadernacion: Cartoné
• Páginas: 396
• Fecha Publicación: 31/01/2014
• Nº Volúmenes: 1
• Idioma: Inglés