Modern Techniques in Applied Molecular Spectroscopy

Transcription

1 Modern Techniques in Applied Molecular Spectroscopy Edited by FRANCIS M. MIRABELLA Equistar Chemicals, LP A Wiley-Interscience Publication JOHN WILEY & SONS, INC. New York Chichester Weinheim Brisbane Singapore Toronto

2 Contents Preface List of Contributors xiii xv 1 Introduction 1 Francis M. Mirabella 1.1. Transmission Spectroscopy Specular Reflectance Spectroscopy Attenuated Total Reflectance Spectroscopy Diffuse Reflectance Spectroscopy Photoacoustic Spectroscopy Infrared Microspectroscopy Raman Microspectroscopy Fiber Optics Techniques Emission Spectroscopy 9 References 10

3 VI Contents 2 Transmission Infrared Spectroscopy 11 Richard W Duerst, Marilyn D. Duerst, and William L. Stebbings 2.1. History 11 Discovery of Infrared Radiation 11 Evolution of Instrumentation for Transmission Infrared Spectroscopy 13 Niche Applications Principles and Theory 15 Molecular Interactions with Electromagnetic Radiation 15 Molecular Vibration-Rotation Theory Instrumentation 30 Infrared Sources 30 Optical Components 34 Detectors 36 Electronics ^ 38 Mounts 38 Noise Sources 38 FFT Algorithms for FT-IR Spectrometers 39 Advantages and Disadvantages of the Different Instrument Systems Experimental Considerations 41 Instrument Performance Evaluation How Do You Know If the Instrument is Functioning Properly? 41 Types of Samples, Sample Preparation Methods 42 Accessory and Methodology Choices 51 Setting up the Instrument for Sample Spectrum Collection 51 Identifying Acceptable Spectra without Artifacts 52 Data Manipulations Interpretation 56 Qualitative Analysis 56 Quantitative Analysis 59 Calculated Spectra Experimental Results and Case Studies 64 Water in the Gaseous State 64 Quantitative Analysis of Xylene Mixtures 67 Molecular Orientation Studies Courses, Users' Groups, and Meetings 70

4 Contents Vll References 71 Glossary 80 3 Specular Reflection Spectroscopy 83 Robert J. Lippert, Brian D. Lamp, and Marc D. Porter 3.1. Introduction Theoretical Considerations 84 Propagation of Electromagnetic Radiation through a Nonconducting Homogeneous Medium 85 Reflection of Electromagnetic Radiation at a Boundary between Homogeneous Media of Different Optical Properties 89 Band Distortions 95 Orientation Analysis Experimental Considerations Applications 110 Organized Thin Films 110 Redox Transformations at Electrochemical Interfaces 114 Aluminum Nitride Thin-Film Characterization Conclusions and Prospectus 124 References Attenuated Total Reflection Spectroscopy 127 Francis M. Mirabella 4.1. Introduction History Principles and Theory Practical Considerations Advantages and Disadvantages 153 Advantages 153 Disadvantages Spectral Regions and Spectral Techniques Employing ATR Applications of ATR Spectroscopy 160 Surface Chemistry 160 Surface Orientation 175 Specific Experimental Details Conclusion 183 References 183

5 Vlll Contents 5 Diffuse Reflectance Spectroscopy 185 Jonathan P. Blitz 5.1. Introduction Role of Diffuse Reflectance in Molecular Spectroscopy Diffuse Reflectance Theory and Practice 189 Fresnel and Kubelka-Munk Reflectance 189 Kubelka-Munk Theory 192 The Practice of Diffuse Reflectance Spectroscopy Applications of Diffuse Reflectance Spectroscopy 208 Diffuse Reflectance UV-Visible Spectroscopy 208 Diffuse Reflectance Near-Infrared Spectroscopy 209 Diffuse Reflectance Mid-Infrared Spectroscopy Conclusions 216 References Photoacoustic Spectroscopy 221 J. F. McClelland, S. J. Bajic, R. W. Jones, and L. M. Seaverson 6.1. Introduction 221 History and Basic Idea of PAS 222 Controllable Sampling Depth 223 Practical Uses of Controllable Sampling Depth Signal Generation Theory and Data Analysis Treatments 225 Magnitude of the Photoacoustic Signal 226 Phase of.the Photoacoustic Signal 227 Photoacoustic Signal Saturation 228 Sampling Depth 230 Interpretation of Photoacoustic Signal Phase Data Instrumentation 236 Photoacoustic Detector 236 FTIR Spectrometer 242 Phase Modulation Applications 248 Rapid Identification of Polymers for Recycling 248 Quantitative Analysis of Major and Minor Concentrations of Additives in Paper Products 249 Analysis of Aqueous Sludges with Soluble and Insoluble Species 251 Quantitation of CaC0 3 Residual in Lime 255

6 Contents ix Determining Surface or Bulk Character of Polymer Additives 257 Fluorination of Polyethylene 259 Chemically Treated Polystyrene Spheres 260 Enhanced Surface Specificity by Linearization of FTIR-PAS Spectra 261 Determination of Coating Thickness from Phase Data Conclusion 264 References Infrared Microspectroscopy 267 Jack E. Katon 7.1. Historical Background Infrared Microscope Sampling Methods of Obtaining IR Spectral Data Qualitative and Quantitative Analysis of Mixtures 283 References Raman Microspectroscopy 291 Andre J. Sommer 8.1. Introduction Raman Effect Signal Production and Collection Instrumentation Detection and Spectral Collection Mode Excitation and Collection of the Raman Scattered Radiation Choice of Microscope Objective Sampling Sampling Problems Spatial Resolution Sample Heating Fluorescence Elimination Polarization Effects 319 References Emission Spectroscopy 323 S. Zhang, F. S. Franke, and T. M. Niemczyk 9.1. Introduction 323

7 X Contents 9.2. Theory 325 Blackbody Radiation 325 Real-Sample (Graybody) Radiation 329 Infrared Emission Spectroscopy of Semitransparent Thin Films 330 Stray Light 333 Emission Band Distortions 334 Temperature Determination Experimental Considerations 338 Spectrometers 338 Constant Temperature IR Emission Attachments 339 Transient Infrared Emission Spectroscopy 341 Multivariate Calibration Applications 343 Gas Phase Studies 343 Small Molecules on Surfaces 345 Characterization of Solid Samples 345 Atmospheric Studies 348 Planetary Observations 348 Minerals and Mineral Deposits 349 Organic Thin Films 351 Dielectric Thin Films Conclusion 371 References Fiber Optics in Molecular Spectroscopy 377 Chris W. Brown Introduction 377 Description of Optical Fibers 377 Internal Reflection Considerations 378 Core-Cladding 379 Evanescent Wave 379 Fiber Throughput Selecting Fibers 380 Optical Regions 380 Single Fibers or Bundles as Probes Interfacing Fibers 386 Spectrometer Accessories 386

8 Contents XI Coupling Fibers to Spectrometer Accessories Sampling Configuration 387 Straight-through Transmission Probes 387 Reflection-Absorption Probes 388 Evanescent Wave Probes 388 Fiber Optic Lenses Applications 390 Drug Dissolution 390 Water Analysis in the Near-IR 393 Gas Analysis in the Near-IR 396 Lamination Monitoring in the Mid-IR Conclusion 400 References 400 Index 403 t