Table Of Content

S E V E N T H E D I T I O N Analytical Chemistry ROBINSON SKELLY FRAME FRAME Undergraduate Instrumental Analysis U n d e r g r a d u a t e SEVENTH EDITION U Crucial to research in molecular biology, medicine, geology, food science, materials n science, and many other fields, analytical instrumentation is used by many scien- d tists and engineers who are not chemists. Undergraduate Instrumental Analysis, e I n s t r u m e n t a l Seventh Edition provides users of analytical instrumentation with an understanding r of these instruments, covering all major fields of modern instrumentation. Following g the tradition of earlier editions, this text is designed for teaching undergraduates r and those with no analytical chemistry background how contemporary analytical a instrumentation works, as well as its uses and limitations. d A n a l y s i s Each chapter provides a discussion of the fundamental principles underlying the u techniques, descriptions of the instrumentation, and numerous applications. The a chapters also contain updated bibliographies and problems, and most have St suggested experiments appropriate to the techniques. This completely revised Ee and updated edition covers subjects in more detail, such as a completely revised V x-ray chapter, expanded coverage of electroanalytical techniques, and expansion EI Nn of chromatography and mass spectrometry topics to reflect the predominance Ts of these instruments in laboratories. This includes state-of-the-art sample H t introduction and mass analyzers and the latest developments in UPLC and Er hyphenated techniques. The book also contains new graphics and addresses D u several new topics: I Tm (cid:127) Ion mobility spectrometry I Oe (cid:127) Time domain NMR (relaxometry) N n (cid:127) Electron spin resonance spectroscopy (ESR, EPR) t (cid:127) Forensic science and bioanalytical applications a (cid:127) Microcalorimetry and optical thermal instruments l (cid:127) Laser-induced breakdown spectroscopy (LIBS) A This text uniquely combines instrumental analysis with organic spectral interpreta- n tion (IR, NMR, and MS). It provides detailed coverage of sampling, sample a handling, sample storage, and sample preparation. In addition, the authors have l included many instrument manufacturers’ websites, which contain extensive y resources. s i s (cid:127) download the ebook to your computer or ccess it anywhere with an internet browser (cid:127) search the full text and add your own notes and highlights (cid:127) link through from references to PubMed 61356 S E V E N T H E D I T I O N U n d e r g r a d u a t e I n s t r u m e n t a l A n a l y s i s James W. Robinson Department of Chemistry, Louisiana State University Baton Rouge, Louisiana, USA Eileen M. Skelly Frame Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute Troy, New York, USA George M. Frame II Wadsworth Laboratory, New York State Department of Health Albany, New York, USA Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business The image on the cover is an example of single crystal x-ray diffractometry. The image is a composite made from five diffraction images covering five degrees of oscillation from a crystal of sulfanilamide (para-aminobenzenesulfonamide), collected on a Rigaku XtaLAB mini by Lee M. Daniels, Ph.D., director, Small Molecule Crystallography, Rigaku Americas Corporation, The Woodlands, TX. www.rigaku.com/smc. © Rigaku Corporation. With permission. CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2014 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Version Date: 20140225 International Standard Book Number-13: 978-1-4822-3374-2 (eBook - PDF) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the valid- ity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or uti- lized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopy- ing, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright.com (http:// www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com Contents Preface.............................................................................................................................................xxi Acknowledgments ..........................................................................................................................xxv Authors ..........................................................................................................................................xxix Chapter 1 Concepts of Instrumental Analytical Chemistry ...............................................................................1 1.1 Introduction: What Is Analytical Chemistry? .........................................................................1 1.2 Analytical Approach ...............................................................................................................3 1.2.1 Defining the Problem .................................................................................................3 1.2.1.1 Qualitative Analysis ...................................................................................4 1.2.1.2 Quantitative Analysis .................................................................................7 1.2.2 Designing the Analytical Method ............................................................................12 1.2.3 Sampling ..................................................................................................................14 1.2.3.1 Gas Samples .............................................................................................16 1.2.3.2 Liquid Samples .........................................................................................17 1.2.3.3 Solid Samples ...........................................................................................18 1.2.4 Storage of Samples ...................................................................................................18 1.3 Basic Statistics and Data Handling .......................................................................................19 1.3.1 Significant Figures ...................................................................................................19 1.3.2 Accuracy and Precision ...........................................................................................21 1.3.3 Types of Errors .........................................................................................................23 1.3.3.1 Determinate Error ....................................................................................23 1.3.3.2 Indeterminate Error ..................................................................................27 1.3.4 Definitions for Statistics ...........................................................................................28 1.3.5 Quantifying Random Error ......................................................................................29 1.3.5.1 Confidence Limits ....................................................................................33 1.3.5.2 Variance....................................................................................................34 1.3.6 Rejection of Results .................................................................................................35 1.4 Sample Preparation ...............................................................................................................36 1.4.1 Acid Dissolution and Digestion ...............................................................................37 1.4.2 Fusions .....................................................................................................................39 1.4.3 Dry Ashing and Combustion ...................................................................................40 1.4.4 Extraction .................................................................................................................40 1.4.4.1 Solvent Extraction ....................................................................................41 1.4.4.2 Solid-Phase Extraction .............................................................................44 1.4.4.3 QuEChERS ..............................................................................................45 1.4.4.4 Solid-Phase Microextraction ....................................................................46 1.5 Performing the Measurement ................................................................................................49 1.5.1 Signals and Noise .....................................................................................................49 1.5.2 Plotting Calibration Curves .....................................................................................52 1.6 Assessing the Data ................................................................................................................54 1.6.1 Limit of Detection ....................................................................................................55 1.6.2 Limit of Quantitation ...............................................................................................56 Problems ..........................................................................................................................................56 Bibliography .....................................................................................................................................59 iii iv Contents Chapter 2 Introduction to Spectroscopy ...........................................................................................................61 2.1 Interaction between Electromagnetic Radiation and Matter ................................................61 2.1.1 What Is Electromagnetic Radiation? .......................................................................61 2.1.2 How Does Electromagnetic Radiation Interact with Matter? ..................................64 2.2 Atoms and Atomic Spectroscopy ..........................................................................................68 2.3 Molecules and Molecular Spectroscopy ...............................................................................70 2.3.1 Rotational Transitions in Molecules ........................................................................70 2.3.2 Vibrational Transitions in Molecules .......................................................................70 2.3.3 Electronic Transitions in Molecules ........................................................................71 2.4 Absorption Laws ...................................................................................................................72 2.4.1 Deviations from Beer’s Law ....................................................................................75 2.5 Methods of Calibration .........................................................................................................76 2.5.1 Calibration with Standards ......................................................................................76 2.5.2 Method of Standard Additions .................................................................................79 2.5.3 Internal Standard Calibration ..................................................................................82 2.5.4 Errors Associated with Beer’s Law Relationships ...................................................85 2.6 Optical Systems Used in Spectroscopy .................................................................................88 2.6.1 Radiation Sources ....................................................................................................89 2.6.2 Wavelength Selection Devices .................................................................................90 2.6.2.1 Filters ........................................................................................................90 2.6.2.2 Monochromator ........................................................................................90 2.6.2.3 Resolution Required to Separate Two Lines of Different Wavelengths .....94 2.6.3 Optical Slits ..............................................................................................................98 2.6.4 Detectors ................................................................................................................101 2.6.5 Single-Beam and Double-Beam Optics .................................................................101 2.6.6 Dispersive Optical Layouts ....................................................................................104 2.6.7 Fourier Transform Spectrometers ..........................................................................105 2.6.7.1 Advantages of FT Systems .....................................................................107 2.7 Spectroscopic Technique and Instrument Nomenclature....................................................107 Suggested Experiments ..................................................................................................................108 Problems ........................................................................................................................................109 Bibliography ...................................................................................................................................111 Chapter 3 Magnetic Resonance Spectroscopy ...............................................................................................113 3.1 Introduction to Nuclear Magnetic Resonance Spectroscopy ..............................................113 3.1.1 Properties of Nuclei ...............................................................................................114 3.1.2 Quantization of 1H Nuclei in a Magnetic Field ......................................................116 3.1.2.1 Saturation and Magnetic Field Strength .................................................119 3.1.3 Width of Absorption Lines ....................................................................................121 3.1.3.1 Homogeneous Field ................................................................................121 3.1.3.2 Relaxation Time .....................................................................................122 3.1.3.3 Magic Angle Spinning ...........................................................................123 3.1.3.4 Other Sources of Line Broadening .........................................................124 3.2 FT-NMR Experiment ..........................................................................................................124 Contents v 3.3 Chemical Shifts ...................................................................................................................127 3.4 Spin–Spin Coupling ............................................................................................................134 3.5 Instrumentation ...................................................................................................................146 3.5.1 Sample Holder ........................................................................................................146 3.5.2 Sample Probe .........................................................................................................148 3.5.3 Magnet ...................................................................................................................150 3.5.4 RF Generation and Detection ................................................................................151 3.5.5 Signal Integrator and Computer .............................................................................152 3.6 Analytical Applications of NMR ........................................................................................152 3.6.1 Samples and Sample Preparation for NMR ...........................................................153 3.6.2 Qualitative Analyses: Molecular Structure Determination ...................................153 3.6.2.1 Relationship between the Area of a Peak and Molecular Structure ......................................................................................153 3.6.2.2 Chemical Exchange ................................................................................154 3.6.2.3 Double-Resonance Experiments ............................................................155 3.6.3 Interpretation of Proton Spectra ............................................................................160 3.6.3.1 Aliphatic Alkanes, Alkenes, Alkynes, and Alkyl Halides ....................161 3.6.3.2 Aromatic Compounds ............................................................................167 3.6.3.3 Oxygen-Containing Organic Compounds ..............................................170 3.6.3.4 Nitrogen-Containing Organic Compounds ............................................172 3.6.4 13C NMR ................................................................................................................175 3.6.4.1 Heteronuclear Decoupling ......................................................................178 3.6.4.2 Nuclear Overhauser Effect .....................................................................179 3.6.4.3 13C NMR Spectra of Solids ....................................................................180 3.6.4.4 Interpretation of 13C Spectra ..................................................................181 3.6.5 2D NMR ................................................................................................................182 3.6.6 Qualitative Analyses: Other Applications .............................................................189 3.6.7 Quantitative Analyses ............................................................................................191 3.7 Hyphenated NMR Techniques ............................................................................................195 3.8 NMR Imaging and MRI .....................................................................................................195 3.9 Time Domain NMR ............................................................................................................201 3.9.1 Solid Fat Content Determination by TD-NMR .....................................................203 3.9.2 Field Homogeneity and Spin Echo.........................................................................204 3.9.3 Relaxation Time Distribution ................................................................................207 3.9.4 TD-NMR Applications ..........................................................................................208 3.10 Low-Field, Portable, and Miniature NMR Instruments .....................................................209 3.11 Limitations of NMR ............................................................................................................210 3.12 Electron Spin Resonance Spectroscopy ..............................................................................210 3.12.1 Instrumentation ......................................................................................................214 3.12.1.1 Samples and Sample Holders .................................................................217 3.12.2 Miniature ESR Spectroscopy ................................................................................217 3.12.3 ESR Spectra and Hyperfine Interactions ...............................................................217 3.12.4 Applications ...........................................................................................................221 3.12.4.1 Spin Labels and Spin Traps ....................................................................223 3.12.5 CW-ENDOR ..........................................................................................................224 Suggested Experiments ..................................................................................................................226 Problems ........................................................................................................................................227 Bibliography ...................................................................................................................................240 Spectral Databases .........................................................................................................................241 vi Contents Chapter 4 Infrared, Near-Infrared, and Raman Spectroscopy .......................................................................243 4.1 Absorption of IR Radiation by Molecules ..........................................................................244 4.1.1 Dipole Moments in Molecules ...............................................................................245 4.1.2 Types of Vibrations in Molecules ..........................................................................246 4.1.3 Vibrational Motion .................................................................................................248 4.2 IR Instrumentation ..............................................................................................................250 4.2.1 Radiation Sources ..................................................................................................254 4.2.1.1 Mid-IR Sources ......................................................................................255 4.2.1.2 NIR Sources ...........................................................................................256 4.2.1.3 Far-IR Sources ........................................................................................258 4.2.1.4 IR Laser Sources ....................................................................................258 4.2.2 Monochromators and Interferometers ...................................................................258 4.2.2.1 FT Spectrometers ...................................................................................259 4.2.2.2 Interferometer Components ....................................................................263 4.2.3 Detectors ................................................................................................................264 4.2.3.1 Bolometer ...............................................................................................264 4.2.3.2 Thermocouples .......................................................................................265 4.2.3.3 Thermistors ............................................................................................266 4.2.3.4 Golay Detector .......................................................................................266 4.2.3.5 Pyroelectric Detectors ............................................................................266 4.2.3.6 Photon Detectors ....................................................................................267 4.2.4 Detector Response Time ........................................................................................268 4.3 Sampling Techniques ..........................................................................................................268 4.3.1 Techniques for Transmission (Absorption) Measurements ....................................269 4.3.1.1 Solid Samples .........................................................................................269 4.3.1.2 Liquid Samples .......................................................................................271 4.3.1.3 Gas Samples ...........................................................................................273 4.3.2 Background Correction in Transmission Measurements .......................................274 4.3.2.1 Solvent Absorption .................................................................................274 4.3.2.2 Air Absorption .......................................................................................275 4.3.3 Techniques for Reflectance and Emission Measurements .....................................275 4.3.3.1 Attenuated Total Reflectance .................................................................275 4.3.3.2 Specular Reflectance ..............................................................................277 4.3.3.3 Diffuse Reflectance ................................................................................278 4.3.3.4 IR Emission ............................................................................................280 4.4 FTIR Microscopy ................................................................................................................281 4.5 Nondispersive IR Systems...................................................................................................285 4.6 Analytical Applications of IR Spectroscopy ......................................................................287 4.6.1 Qualitative Analyses and Structural Determination by Mid-IR Absorption Spectroscopy .......................................................................................289 4.6.1.1 Hydrocarbons .........................................................................................291 4.6.1.2 Organic Compounds with C–O Bonds ..................................................297 4.6.1.3 Nitrogen-Containing Organic Compounds ............................................302 4.6.1.4 Functional Groups Containing Heteroatoms .........................................305 4.6.2 Quantitative Analyses by IR Spectrometry ...........................................................309 Contents vii 4.7 NIR Spectroscopy ...............................................................................................................313 4.7.1 Instrumentation ......................................................................................................313 4.7.2 NIR Vibrational Bands, Spectral Interpretation, and Calibration .........................314 4.7.2.1 NIR Calibration: Chemometrics ............................................................316 4.7.3 Sampling Techniques for NIR Spectroscopy .........................................................316 4.7.3.1 Liquids and Solutions .............................................................................317 4.7.3.2 Solids ......................................................................................................318 4.7.3.3 Gases ......................................................................................................320 4.7.4 Applications of NIR Spectroscopy ........................................................................320 4.8 Raman Spectroscopy ...........................................................................................................321 4.8.1 Principles of Raman Scattering .............................................................................322 4.8.2 Raman Instrumentation .........................................................................................325 4.8.2.1 Light Sources ..........................................................................................325 4.8.2.2 Dispersive Spectrometer Systems ..........................................................325 4.8.2.3 FT-Raman Spectrometers.......................................................................326 4.8.2.4 Fiber-Optic-Based Modular and Handheld Systems ..............................327 4.8.2.5 Samples and Sample Holders for Raman Spectroscopy ........................330 4.8.3 Applications of Raman Spectroscopy ....................................................................330 4.8.4 Resonance Raman Effect .......................................................................................336 4.8.5 Surface-Enhanced Raman Spectroscopy ...............................................................336 4.8.6 Raman Microscopy ................................................................................................338 4.9 Chemical Imaging Using NIR, IR, and Raman Spectroscopy ...........................................340 Suggested Experiments ..................................................................................................................348 Problems ........................................................................................................................................348 Bibliography ...................................................................................................................................354 Spectral Databases .........................................................................................................................356 Chapter 5 Visible and Ultraviolet Molecular Spectroscopy ...........................................................................357 5.1 Introduction .........................................................................................................................357 5.1.1 Electronic Excitation in Molecules ........................................................................361 5.1.2 Absorption by Molecules .......................................................................................364 5.1.3 Molar Absorptivity ................................................................................................365 5.1.4 Shape of UV Absorption Curves ...........................................................................367 5.1.5 Solvents for UV/VIS Spectroscopy........................................................................370 5.2 Instrumentation ...................................................................................................................370 5.2.1 Optical System .......................................................................................................370 5.2.2 Radiation Sources ..................................................................................................371 5.2.3 Monochromators ....................................................................................................374 5.2.4 Detectors ................................................................................................................374 5.2.4.1 Barrier Layer Cell...................................................................................374 5.2.4.2 Photomultiplier Tube ..............................................................................376 5.2.4.3 Semiconductor Detectors: Diodes and Diode Array Systems ................377 5.2.4.4 Diodes .....................................................................................................379 5.2.4.5 Diode Arrays ..........................................................................................380 5.2.5 Sample Holders ......................................................................................................382 5.2.5.1 Liquid and Gas Cells ..............................................................................382 viii Contents 5.2.5.2 Matched Cells .........................................................................................384 5.2.5.3 Flow-Through Samplers .........................................................................385 5.2.5.4 Solid Sample Holders .............................................................................385 5.2.5.5 Fiber-Optic Probes .................................................................................386 5.2.6 Microvolume, Nanovolume, and Handheld UV/VIS Spectrometers .....................386 5.2.6.1 Microvolume Systems ............................................................................387 5.2.6.2 Variable Path Length Slope Spectroscopy™ System .............................391 5.2.6.3 Handheld Visible Spectroscopy System .................................................394 5.3 UV Absorption Spectra of Molecules .................................................................................395 5.3.1 Solvent Effects on UV Spectra ..............................................................................396 5.3.1.1 Bathochromic or Red Shift ....................................................................396 5.3.1.2 Hypsochromic or Blue Shift ...................................................................396 5.4 UV Spectra and the Structure of Organic Molecules .........................................................398 5.4.1 Conjugated Diene Systems ....................................................................................398 5.4.2 Conjugated Ketone Systems ..................................................................................401 5.4.3 Substitution of Benzene Rings ...............................................................................404 5.5 Analytical Applications ......................................................................................................406 5.5.1 Qualitative Structural Analysis ..............................................................................406 5.5.2 Quantitative Analysis .............................................................................................407 5.5.3 Multicomponent Determinations ...........................................................................412 5.5.4 Other Applications .................................................................................................413 5.5.4.1 Reaction Kinetics ...................................................................................413 5.5.4.2 Spectrophotometric Titrations ................................................................414 5.5.4.3 Spectroelectrochemistry .........................................................................415 5.5.4.4 Analysis of Solids ...................................................................................415 5.5.5 Measurement of Color ...........................................................................................416 5.6 Accuracy and Precision in UV/VIS Absorption Spectrometry ..........................................418 5.7 Nephelometry and Turbidimetry .........................................................................................419 5.8 Molecular Emission Spectrometry ......................................................................................420 5.8.1 Fluorescence and Phosphorescence .......................................................................420 5.8.2 Relationship between Fluorescence Intensity and Concentration .........................423 5.9 Instrumentation for Luminescence Measurements .............................................................425 5.9.1 Wavelength Selection Devices ...............................................................................425 5.9.2 Radiation Sources ..................................................................................................426 5.9.3 Detectors ................................................................................................................428 5.9.4 Sample Cells ..........................................................................................................428 5.9.5 Spectrometer Systems ............................................................................................428 5.10 Analytical Applications of Luminescence ..........................................................................429 5.10.1 Advantages of Fluorescence and Phosphorescence ...............................................431 5.10.2 Disadvantages of Fluorescence and Phosphorescence ..........................................431 Suggested Experiments ..................................................................................................................432 Problems ........................................................................................................................................434 Bibliography ...................................................................................................................................439 Chapter 6 Atomic Absorption Spectrometry ..................................................................................................441 6.1 Absorption of Radiant Energy by Atoms ............................................................................441 6.1.1 Spectral Linewidth .................................................................................................444