Practical Mass Spectrometry A Contemporary Introduction

Practical Mass Spectrometry A Contemporary Introduction

Edited by

Brian S. Middleditch University of Houston Houston, Texas

PLENUM PRESS • NEW YORK AND LONDON

Library of Congress Cataloging in Publication Data

Main entry under title:

Practical mass spectrometry.

Includes bibliographies and index. 1. Mass spectrometry. I. Middleditch, Brian S.

QD96.M3P72 545'.33 ISBN-13: 978-1-4613-2984-8 e-ISBN-I3: 978-1-4613-2982-4 001: 10.1007/978-1-4613-2982-4

© 1979 Plenum Press, New York Softcover reprint of the hardcover I st edition 1979 A Division of Plenum Publishing Corporation 227 West 17th Street, New York, N.Y. 10011

All rights reserved

79-351

No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, microfilming, recording, or otherwise, without written permission from the Publisher

Contributors

Thomas Aczel, Exxon Research and Engineering Company, Baytown, Texas 77520

Charles J. W. Brooks, Department of Chemistry, University of Glasgow, Glasgow GI2 8QQ, Scotland

Edward C. M. Chen, School of Sciences and Technologies, University of Houston at Clear Lake City, Houston, Texas 77058

Charles G. Edmonds, Department of Chemistry, University of Glasgow, Glasgow GI2 8QQ, Scotland. Present address: Divisao Quimica, Instituto Nacional de Pesquisas da Amazonia, Manaus, Amazonas, Brasil

Stephen R. Heller, U. S. Environmental Protection Agency, MIDSD, PM-2I8, Washington, D. C. 20460

H. D. M. Jager, Atomic Weapons Research Establishment, Aldermaston, Reading, Berkshire RG7 4PR, England

David C. Maxwell, Atomic Weapons Research Establishment, Aldermaston, Reading, Berkshire RG7 4PR, England

Andrew McCormick, Atomic Weapons Research Establishment, Aldermaston, Reading, Berkshire RG7 4PR, England

Brian S. Middleditch, Department of Biophysical Sciences, University of Houston, Houston, Texas 77004

Daryl Nooner, Department of Biophysical Sciences, University of Houston, Houston, Texas 77004. Present address: Spectrix Corporation, Houston, Texas 77054

J. Oro, Department of Biophysical Sciences, University of Houston, Houston, Texas 77004

v

vi Contributors

Henry Shan field , Department of Chemistry, University of Houston, Houston, Texas 77004

Richard N. Stillwell, Institute for Lipid Research, Baylor College of Medicine, Houston, Texas 77030

William 1. A. VandenHeuvel, Merck, Sharp and Dohme Research Laboratories, Rahway, New Jersey 07065

Anthony G. Zacchei, Merck Institute for Therapeutic Research, West Point, Pennsylvania 19486

Albert Zlatkis, Department of Chemistry, University of Houston, Houston, Texas 77004

Preface

It has been estimated that more than 8090 of the world's scientists who have ever lived are still alive today. It would not be unreasonable to suggest that more than 95% of those who have ever used a mass spectrometer are not only alive but are still actively employed. Most have never had any formal training in the subject since, with a few notable exceptions, universities have only recently begun to offer courses in mass spectrometry.

We have written this book for the student of modern mass spectro­metry: it is for the novice who wished to know what the instruments can do and how the techniques can be applied. There are other books on the market which delve into the history of mass spectrometry and go deeply into the mathematical theory and instrumentation. There are yet more books which guide one through the art of interpreting spectra. We have deliberately avoided these topics so that the reader is confronted only with the basic principles and is allowed a taste of the applications.

One of the best methods of deVeloping a useful textbook is to teach a course based upon its content. This is what we did. We met in Houston in 1976 to teach a course on "Perspectives in Mass Spectrometry" and to coordinate our writing. The authors of five of the chapters met again in St. Louis in 1978 to teach a course on combined gas chromatography-mass spectrometry. The final product is a series of chapters covering the major aspects of the subject, often written by those who developed them. Some fairly heavy editing was required to maintain uniformity in style, but the characteristic styles of the individual authors have been largely preserved.

The first chapter is for the true neophyte. In the second chapter, rather than discuss all of the various components which can be assembled to produce a working instrument, discussion has been limited to three commercial machines. The LKB 9000 is similar to the LKB 9000S referred to in several of the other chapters. Likewise, the Hewlett-Packard 5992 is one of the latest of the quadrupole instruments, a descendent of the H.-P.

vii

viii Preface

5390 referred to in Chapter 4. The reader is introduced to gas chromatog­raphy-mass spectrometry (GC-MS) in Chapter 3, and a more detailed discussion of selective ion monitoring follows in the next chapter. The special problems associated with the analysis of volatile samples are reviewed in Chapter 5, and automatic data processing is discussed in Chapter 6. Since those who are new to mass spectrometry will initially, at least, identify compounds by comparison with spectra in reference collec­tions, the next three chapters review the tools that are available to accomplish this. The final four chapters provide a sampling of the appli-cations for which mass spectrometry is most suited. .

The exercises provided in most chapters are designed to allow the student to evaluate his comprehension of the subject matter. Answers to problems are given at the end of the book. We have also provided lists of selected review articles and books for further reading.

In addition to the 16 authors of the various chapters, many other individuals and companies have made minor, but valuable, contributions. Some of these are acknowledged in the text. Among the others are Kratos­AEI for suggesting that we undertake this task and for underwriting our first course, and the following: Chapter 2-LKB Instruments, Hewlett­Packard, and Kratos-AEI for providing information concerning their instruments and some of the illustrations; Chapter 3-the Medical Re­search Council and Science Research Council for support of much of the work described, colleagues and co-workers in many laboratories for assistance and support, and special thanks to E.C. Horning for research facilities at Baylor College of Medicine, Houston, Texas; Chapter 5-the National Aeronautics and Space Administration, Life Sciences Directorate, Johnson Space Center, Houston, Texas (Contract NAS 9-14534); Chapter 6-the National Institutes of Health (GM-1390l) and the Robert A. Welch Foundation (Q-125); Chapter 7-J.A. McCloskey for collaborating in the production of the "Guide to Collections of Mass Spectral Data," upon which this chapter is based; Chapter 8-Her Majesty's Stationery Office for permission to reprint excerpts from the Mass Spectrometry Bulletin; Chapter 9-the following persons, who have worked on and contributed to the Mass Spectral Search System (MSSS): K. Biemann (MIT); A. Bridy, H.M. Fales, R.J. Feldmann, and G.W.A. Milne (NIH); R.S. Heller (University of Maryland); D.C. Maxwell and A. McCormick (Mass Spec­trometry Data Centre); W.L. Budde and J.M. McGuire (Environmental Protection Agency); and F.W. McLafferty (Cornell University); Chapter JO-colleagues at the U.S. Environmental Protection Agency whose re­search is described, including R.G. Webb (Power Plant Cooling Water); L.H. Keith (Industrialized Shipping Channel); J.W. Eichelberger, W.M. Middleton, and W.L. Budde (Municipal Drinking Water); and R.G. Weber and C.E. Taylor (Landfill Leachate); Chapter II-the following colleagues

Preface ix

who have contributed to the research described: B. Arison, J. Carlin, M. Christy, S. Date, B. Ellsworth, V. Gruber, K. Hooke, H.B. Hucker, T. Jacob, C. Porter, R.E. Rhodes, A. Rosegay, J. Smith, D.J. Tocco, T. Tyler, S. Vickers, R. Walker, L.L. Weidner, T.!. Wishousky, D. Wolf, F. Wolf, and O. Woltersdorf; Chapter 13-present and former students and colleagues working in cooperation with J. Oro whose research forms the basis of this article, the National Aeronautics and Space Administration for research support, and authors and publishers for permission to use copyrighted figures and tables.

I would like to thank Ellis Rosenberg and Robert Golden of Plenum Press, who skillfully and efficiently expedited the book through its various stages of production.

lowe a special debt to my wife, Tin Tin, and my daughter, Courtney, for their patience while I was working on the manuscript.

University of Houston Brian S. Middleditch

Contents

1. Principles of Mass Spectrometry Brian S. Middleditch 1. History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 2. The Electron Impact Mass Spectrum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2

2.1. The Molecular Ion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3 2.2. Fragment Ions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9 2.3. Multiply Charged Ions .................................................. 15 2.4. Metastable Peaks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 16 2.5. Ion-Molecule Reactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 16 2.6. Variation of Electron Energy ............................................ 17 2.7. Quadrupole Mass Filters ................................................ 21

3. Alternative Methods of Ionization ............................................ 21 3.1. Chemical Ionization .................................................... 21 3.2. Field Ionization ........................................................ 22 3.3. Field Desorption ....................................................... 23

4. Exercises .................................................................. 23 5. Suggested Reading .......................................................... 23

2. Instrumentation for Mass Spectrometry Brian S. Middleditch

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 25 2. The LKB 9000 Instrument ................................................... 25

2.1. Electron-Impact Ion Source ............................................. 26 2.2. Flight Tube ............................................................ 29 2.3. Total Ion Current Detector .............................................. 29 2.4. Electromagnet ......................................................... 30 2.5. Spectrum Detection and Recording ....................................... 31 2.6. Gas Chromatographic Inlet .............................................. 32 2.7. Other Inlet Systems .................................................... 35 2.8. Multiple Ion Detector ................................................... 36 2.9. Similarity to Other Instruments .......................................... 37

3. The Hewlett-Packard 5992 Instrument ......................................... 38 3.1. General Description .................................................... 38

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xii Contents

3.2. The Mass Analyzer ..................................................... 40 3.3. Use of the Instrument. .................................................. 40 3.4. Other Accessories ...................................................... 47 3.5. Similarity to Other Instruments .......................................... 47

4. The Kratos-AEI MS50 Instrument ............................................ 47 4.1. Resolution ............................................................. 48 4.2. Inlet Systems .......................................................... 49 4.3. Ion Sources ............................................................ 49 4.4. Ion Analyzer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 50 4.5. Detector ............................................................... 53 4.6. Matrix Control System .................................................. 54 4.7. Data Handling ......................................................... 54 4.8. Similarity to Other Instruments .......................................... 54

5. Exercises .................................................................. 54 6. Suggested Reading ................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 55

3. Combined Gas Chromatography-Mass Spectrometry Charles J. W. Brooks and Charles G. Edmonds 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 57

1.1. Gas-Phase Techniques in Analytical Chemistry ......... . . . . . . . . . . . . . . . . .. 57 1.2. Combined Gas Chromatography-Mass Spectrometry. . . . . . . . . . . . . . . . . . . . .. 58 1.3. Role of GC -MS in Relation to Other Techniques ......................... 59

2. Gas Chromatography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 59 2.1. Introduction .......................................................... 59 2.2. Basic Principles. . . . . . . .. . . . . . . . . . . . .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 61 2.3. Features of the Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 65 2.4. Standardization of Retention Behavior. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 67 2.5. Derivatives and the Discriminative Power of Gas Chromatography. . . . . . . . .. 71

3. Gas Chromatography-Mass Spectrometry .................................... 76 3.1. The Interface ......................................................... 76 3.2. Additional Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 80 3.3. Derivatives for GC-MS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 83

4. Selected Applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 90 4.1. Samples Not Requiring Derivatization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 90 4.2. "On-Column" Transformations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 94 4.3. Derivatives Promoting Informative Fragmentations. . . . . . . . . . . . . . . . . . . . . . .. 96 4.4. Analysis of Closely Related Unsaturated Steroids ......................... 100 4.5. Studies of Drug Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 104 4.6. Protection of Thermally Labile Samples by Derivative Formation. . . . . . . . . .. 109 4.7. Applications of Selective Derivatization Reagents. . . . . . . . . . . . . . . . . . . . . . . .. 117 4.8. Use of Isotope-Labeled Reagents ....................................... 121

5. Exercises ................................................................. 125 6. Suggested Reading ......................................................... 125

4. Selective Ion Monitoring Edward C. M. Chen

I. Introduction............................................................... 127 2. Operational Variables in Selective Ion Monitoring ............................. 129

2.1. Mass Spectrometric Variables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 130 2.2. Gas Chromatographic Variables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 132

Contents xiii

3. Instrument Operation for Selective Ion Monitoring ............................. 132 3.1. Monitoring of a Finite Number of Chosen Ions ........................... 133 3.2. Repetitive Scanning and SIM Profile Reconstruction ...................... 134

4. Procedures for the Development of SIM Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 135 4.1. Analysis of Trace (Picogram) Quantities ................................. 136 4.2. Analyses Using Reconstructed SIM Profiles .............................. 140 4.3. Additional Considerations .............................................. 145

5. Applications of SIM to Other Fields of Study ................................. 146 6. Summary ................................................................. 148 7. Exercises ................................................................. 149 8. Suggested Reading ......................................................... 149

5. Concentration Techniques for Volatile Samples Albert Zlatkis and Henry Shanjield I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 151 2. Selective Adsorption ....................................................... 152

2.1. Selective Adsorption Using Tenax-GC Polymer ........................... 152 2.2. Selective Adsorption Using Carbopack B ................................ 159

3. Exercises ................................................................. 159 4. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 160

6. Automatic Data Processing Richard N. Stillwell

I. Introduction ............................................................... 161 2. Instrument Control and Data Acquisition ..................................... 161 3. The Minicomputer ......................................................... 165 4. Interrupts and Asynchronous Processing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 167 5. Interfacing ................................................................ 168 6. Timing .................................................................... 169 7. Designing the Interface .... " ............................................... 171 8. Designing the Software ..................................................... 174 9. Exercises ................................................................. 178

7. Collections of Mass Spectral Data Brian S. Middleditch

I. Introduction ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 179 2. Open-Ended Data Collections ............................................... 179 3. Published Data Collections .................................................. 183 4. Donations of Spectra. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 187 5. Exercise .................................................................. 187 6. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 187

8. The Mass Spectrometry Data Centre H.D.M. Jager. David C. MaxlI·ell. and Andrew McCormick

1. History and Organization ................................................... 189 2. Activities of the Centre ..................................................... 190

2.1. The Mass Spectrometry Bulletin ........................................ 191

xiv Contents

2.2. Collection and Dissemination of Mass Spectra ............................ 201 2.3. Assistance in Compound Identification by Mass Spectrometry ............. 202

3. Suggested Reading ......................................................... 207

9. The Mass Spectral Search System Stephen R. Heller

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 209 2. History and Organization ................................................... 210. 3. The Mass Spectral Search System ........................................... 212

3.1. Current MSSS Use .................................................... 214 3.2. Future Development of the MSSS ....................................... 215

4. Suggested Reading ......................................................... 217

10. Environmental Applications of Mass Spectrometry Stephen R. Heller

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 219 2. Drinking Water Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 222

2.1. Experimental Procedure ................................................ 222 2.2. Interpretation of Results ............................................... 223 2.3. Analytical Quality Assurance ........................................... 229

3. Study of a Landfill Leachate ................................................ 231 4. A Study of the Houston Ship Channel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 236 5. Summary ................................................................. 239 6. Exercises ................................................................. 240 7. Suggested Reading ......................................................... 240

11. Applications of Mass Spectrometry in the Pharmaceutical Industry Anthony G. Zacchei and William 1. A. VandenHeuvel

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 241 2. Drug Metabolism .......................................................... 241

2.1. Gas Chromatography-Mass Spectrometry ................................ 242 2.2. Gas Chromatography-High-Resolution Mass Spectrometry ................ 249 2.3. Direct-Probe Mass Spectrometry ........................................ 255 2.4. Derivatization ......................................................... 266 2.5. Repetitive Scanning and Selective Ion Monitoring ......................... 267 2.6. Stable Isotopes ........................................................ 277

3. Medicinal Chemistry ....................................................... 284 4. Pharmaceutical Preparations ................................................ 285 5. Summary ................................................................. 287 6. Exercises ................................................................. 287 7. Suggested Reading ......................................................... 288

12. Applications of Mass Spectrometry in the Petrochemical Industry Thomas Aczel

I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 289 1.1. The Role of Mass Spectrometry in the Petrochemical Industry ............. 289 1.2. Historical Background ................................................. 290

Contents xv

2. Methods .................................................................. 291 2.1. Methods for Qualitative Analysis ........................................ 291 2.2. Spectral Features of Major Compound Types in Petroleum- and

Coal-Derived Materials ................................................. 292 2.3. General Approach for Structure Identification ............................ 299 2.4. Principles of Quantitative Analysis ...................................... 301 2.5. Simplifying Approaches ................................................ 303

3. Applications of High- and Ultrahigh-Resolution Instruments .................... 307 3.1. Computer Programs for Handling High-Resolution Mass Spectra ........... 311 3.2. Measurements of Peak Intensities and Positions ........................... 312 3.3. Reference Standards ................................................... 313 3.4. Mass Measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 313 3.5. Formula Assignment ................................................... 314 3.6. Determination of Average Sample Properties ............................. 318

4. Established Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 319 5. Miscellaneous Applications ................................................. 320 6. Future Research ........................................................... 321 7. Exercises ................................................................. 322 8. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 324

13. Cosmochemical and Geochemical Applications of Mass Spectrometry J. Oro and Daryl Nooner

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 327 2. Meteorites ................................................................ 328 3. Abiotic Synthesis .......................................................... 335 4. Lunar Samples ............................................................ 344 5. Ancient Sediments ......................................................... 349 6. Viking Mission to Mars. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 355 7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 358 8. Exercises ................................................................. 358 9. Suggested Reading ......................................................... 358

Solutions to Exercises ................................................ 361

Index ..................................................................... 369