Introduction to Mass Spectrometry E-Book

J. Throck Watson

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 1890

Veröffentlichungsjahr: 2013

Beschreibung

Completely revised and updated, this text provides an easy-to-read guide to the concept of mass spectrometry and demonstrates its potential and limitations. Written by internationally recognised experts and utilising "real life" examples of analyses and applications, the book presents real cases of qualitative and quantitative applications of mass spectrometry. Unlike other mass spectrometry texts, this comprehensive reference provides systematic descriptions of the various types of mass analysers and ionisation, along with corresponding strategies for interpretation of data. The book concludes with a comprehensive 3000 references.

This multi-disciplined text covers the fundamentals as well as recent advance in this topic, providing need-to-know information for researchers in many disciplines including pharmaceutical, environmental and biomedical analysis who are utilizing mass spectrometry

Leseprobe

Contents

Preface

Acknowledgments

Chapter 1 Introduction

I. Introduction

II. History

III. Some Important Terminology Used In Mass Spectrometry

IV. Applications

V. The Need for Chromatography

VI. Closing Remarks

VII. Monographs on Mass Spectrometry Published Before 1970

Chapter 2 The Mass Spectrometer

I. Introduction

II. Ion Guides

III. Types of m/z Analyzers

IV. Calibration of the m/z Scale

V. Ion Detectors

VI. Vacuum Systems

Chapter 3 Mass Spectrometry/Mass Spectrometry

I. Introduction

II. Ion Dissociation

III. Instrumentation for MS/MS

IV. Specialized Techniques and Applications

V. Analyte Identification from MS/MS Data

VI. Concluding Remarks about MS/MS

Chapter 4 Inlet Systems

I. Introduction

II. Batch Inlets

III. Continuous Inlets

IV. Ionization Inlet Systems

V. Speciality Interfaces

VI. Final Statement

Chapter 5 Strategies for Data Interpretation (Other than Fragmentation)

I. Introduction

II. Some Important Definitions

III. Possible Information That Can Be Obtained from the Mass Spectrum

IV. Elemental Composition of an Ion and the Ratios of Its Isotope Peaks

V. Identifying the Mass of an Analyte

VI. Recognition of Spurious Peaks in the Mass Spectrum

VII. Obtaining Structural Information from the Mass Spectrum

Chapter 6 Electron Ionization

I. Introduction

II. Ionization Process

III. Strategy for Data Interpretation

IV. Types of Fragmentation Pathways

V. Representative Fragmentations (Spectra) of Classes of Compounds

VI. Library Searches and EI Mass Spectral Databases

VII. Summary of Interpretation of EI Mass Spectra

Chapter 7 Chemical Ionization

I. Introduction

II. Description of the Chemical Ionization Source

III. Production of Reagent Ions from Various Reagent Gases

IV. Positive-Ion Formation Under CI

V. Negative-Ion Formation under CI

VI. Data Interpretation and Systematic Studies of CI

VII. Ionization by Charge Exchange

VIII. Atmospheric Pressure Chemical Ionization

IX. Desorption Chemical Ionization

X. General Applications

XI. Concluding Remarks

Chapter 8 Electrospray Ionization

I. Introduction

II. Operating Principles

III. Appearance of ESI Mass Spectra and Data Interpretation

IV. ESI with an m/z Analyzer of High Resolving Power

V. Conventional ESI Source Interface

VI. Nanoelectrospray and Microelectrospray Ionization

VII. Desorption Electrospray Ionization (DESI)

VIII. Effect of Composition and Flow Rate of an Analyte Solution

IX. Special Applications

X. General Applications of ESI

Chapter 9 MALDI

I. Historical Perspective and Introduction

II. Operating Principles

III. Sample Handling

IV. Special Instrumental Techniques

V. Representative Applications

Chapter 10 Gas Chromatography/Mass Spectrometry

I. Introduction

II. Introduction to GC

III. Sample Handling

IV. Instrument Requirements for GC/MS

V. Operational Considerations

VI. Sources of Error

VII. Representative Applications of GC/MS

VIII. Special Techniques

Chapter 11 Liquid Chromatography/Mass Spectrometry

I. Introduction

II. Historical Milestones in the Development of the Interface

III. Currently Viable Versions of the Interface

IV. Special Operation of LC under MS Conditions

V. Applications

Chapter 12 Analysis of Proteins and Other Biopolymers

I. Introduction

II. Proteins

III. Oligonucleotides

IV. Carbohydrates

Subject Index

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Reprinted with corrections March 2008

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Library of Congress Cataloging-in-Publication Data

Watson, J. Throck.

Introduction to mass spectrometry : instrumentation, applications, and

strategies for data interpretation / J. Throck Watson, O. David Sparkman.

-- 4th ed.

p. cm.

Includes index.

ISBN 978-0-470-51634-8 (cloth)

1. Mass spectrometry. 2. Biomolecules--Analysis. I. Sparkman, O. David

(Orrin David), 1942- II. Title.

QC454.M3W38 2007

543’.65--dc22

2007024030

British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

ISBN 978-0470-51634-8 (H/B)

Preface

This edition of Introduction to Mass Spectrometry is far more than a revision of the third edition, which appeared in 1997. Completely updated and more than 75% rewritten, it covers strategies for data interpretation, fundamental operating principles of instrumentation, and representative applications for all areas of organic, environmental, and biomedical mass spectrometry. A majority of the chapters have bibliographies containing several hundred references to research articles and reviews, mostly published since 2000. Most chapters, but especially the first two, provide a historical perspective on the development of mass spectrometry as well as commentary on the evolution of commercial developments of the instrumentation. Careful attention to nomenclature is provided throughout the book. In addition to serving as a general reference for the subject of mass spectrometry as it pertains to organic and biochemistry, this book is designed for use as a textbook for courses on mass spectrometry. The readily comprehensible approach to the topic, honed through the teamwork of the coauthors in teaching hundreds of classes on various aspects of mass spectrometry for nearly 30 years under the auspices of the American Chemical Society, will benefit the reader.

The physical instrument is dissected and described in Chapter 2 in a systematic manner from the ion source through ion guides to the m/z analyzer to the detection system with attention to the vacuum system. The fundamental physics for each type of m/z analyzer, as well as for common detectors and vacuum pumps, are provided together with a “common sense” description of the operating principles of each.

Chapter 3 describes the concept of MS/MS with emphasis on collisionally activated dissociation. Tandem-in-space is distinguished from tandem-in-time, and several qualitative and quantitative applications of both types of technology are presented in the context of environmental and biomedical fields. In addition, information on analyte identification from MS/MS is provided along with explanations and sources of spectral databases and how to use them.

Various means of transporting the sample into the low-pressure environment of the mass spectrometer are described in Chapter 4. The operating mechanics of “batch” inlet systems as well as continuous sampling systems are presented together with representative and/or illustrative examples. Descriptions of nonchromatographic continuous inlets include DART, DESI, DAPCI, SIFT, MIMS, CRIMS, pyrolysis, electrophoresis, laser ablation, continuous-flow FAB, and ICP. Continuous inlets in combination with chromatography include SFC and pyrolysis GC and are presented in Chapters 10 and 11, respectively.

A general strategy for interpretation of a mass spectrum, regardless of the type of ionization involved, is presented in Chapter 5. The Nitrogen Rule is introduced and used in a variety of situations. The importance of isotope peak-intensity ratios is introduced; several carefully detailed examples are described that show the relationship between isotope peak-intensity ratios and the elemental composition of the corresponding ion. The basis for recognizing peaks representing odd-electron vs even-electron ions is introduced; the importance of recognizing such ions is illustrated with appropriate examples of mass spectra resulting from a variety of ionization types, including Ei, CI, and electrospray.

Chapter 6 is one of the highlights of the book, providing a solid introduction to the formation, appearance, and interpretation of EI mass spectra. Emphasis is placed on recognizing the most probable site of electron deficiency (site of the. •, the “plus/dot”) in the molecular ion, which is the precursor of a majority of the ions represented by the fragmentation pattern in an EI mass spectrum. Four major pathways of fragmentation of a molecular ion (sigma-bond cleavage, homolytic cleavage, heterolytic cleavage, and hydrogen-shift rearrangements) are introduced in a clear manner, then supported systematically with nearly 100 fragmentation schemes to facilitate interpretation of dozens of representative mass spectra of various types of compounds. This chapter also includes detailed information on EI mass spectral databases and library search programs along with descriptions of their use.

The basis for chemical ionization is described in Chapter 7. Whereas positive-ion formation is emphasized, attention is also given to negative-ion formation, with careful distinction between negative-ion CI (NCI, the result of an ion/molecule reaction involving an anion) and electron capture negative ionization (ECNI), a resonant process involving capture of a thermal electron. Atmospheric pressure CI (APCI) is introduced, which serves as an important interface for LC/MS applications that are not amenable to electrospray ionization. The specialized technique of desorption CI (DCI) is also described. Descriptions of the various types of CI are supported with illustrative examples of application to environmental and biomedical problems.

The operating principles of electrospray ionization (ESI) are described in Chapter 8 together with some of the mechanical aspects of the interface that make it one of the most viable for LC/MS applications. The basis for automated computation of the mass of the analyte is illustrated in an example that dissects the peaks in an ESI mass spectrum and sets up simultaneous equations based on first principles relating to the m/z value of the mass spectral peaks. Although introduced in Chapter 4, the developing technique of DESI is covered. Many current applications of the ESI technology are reviewed, which results in more than 300 references in this chapter.

The operating principles of matrix-assisted laser desorption/ionization (MALDI) are described in Chapter 9, including some commentary on current theories of the mechanism of ionization. Attention is given to sample preparation, including descriptions of specialized sample probes to facilitate sample cleanup. Examples of typical MALDI spectra are described to illustrate the effect and use of delayed extraction and ion mirrors (reflectrons). The technology of atmospheric pressure MALDI (AP MALDI) is described. Many current applications of MALDI technology are reviewed, also making this chapter rich in citations (more than 500).

Chapter 10 describes the basis for trade-offs in individual operation of GC and MS that are necessary for successful operation of the combined technique. Introductory protocols for proper syringe/sample handling in the mature technology of GC/MS are presented. The important technology of selected ion monitoring (SIM) is described in the context of qualitative and quantitative applications in the biomedical and environmental fields. Strategies and procedures for data processing with mass chromatograms are described in the context of suspected overlapping data obtained from samples containing chromatographically unresolved components. Some current applications of the technology are reviewed along with explanations of software used for component deconvolution through processing complex data. This chapter has nearly 200 references.

Chapter 11 on LC/MS emphasizes how conventional protocols of HPLC operation must be modified to become compatible with MS operation for combined operation. Although electrospray is the dominant interface for LC/MS, the specialized ionization techniques of APCI and APPI (atmospheric pressure photoionization), which lend themselves to particular applications, are given serious consideration. Several current applications of LC/MS technology are reviewed resulting in almost 250 citations.

Methodology for proteomics is emphasized in Chapter 12, which also describes some basic approaches to the characterization of carbohydrates and nucleotides. The strategy and procedure for sequencing a peptide from CAD MS/MS data are described in detail as supported by results for a simple didactic example. The concept of peptide mass mapping is described, which is the basis, sometimes in combination with data from CAD MS/MS, for automated identification of proteins by software that is often purchased as part of a data system or that is used in conjunction with notable Web sites for such purposes. Methodology for identifying/characterizing a variety of post-translational modifications to proteins, including phosphorylation and disulfide-bond formation, is described in the context of several step-by-step examples. Hundreds of current applications are reviewed, bringing the number of references in this chapter to more than 800.

Because the book is designed for use as a textbook for courses on mass spectrometry, Power Point presentations, including figures from the book and animations developed by the authors, are available for downloading to site-registered instructors to support their teaching efforts. For the benefit of students, the authors will maintain a Web site (through and with the support of the publisher) that will contain exercises together with downloadable answer keys. These materials will be updated on a regular basis.

“Determination is often the first chapter in the book of excellence.”

~Unknown

Acknowledgments

Many of the realistic examples of mass spectral data and applications of mass spectrometry derive from experiments conducted in the Watson Laboratory by some 50 Ph.D. graduate students or postdoctoral fellows in the context of biomedical research applications. Recent contributors include graduate assistants Xue Li, Jose-Luis Gallegos-Perez, Nalini Sadagopan, Naxing Xu, Yingda Xu, Wei Wu, Jianfeng Qi, David Wagner, and professorial students Heidi Bonta, Brad Sauter, and Greg Boyd. Other illustrative applications of mass spectrometry derive from the Sparkman Laboratory, with the help of Teresa Vail and Matthew Curtis, in the context of environmental chemistry and computational approaches to preparing and interrogating standard libraries of mass spectra. Thanks to Leslie Behm and Susan Kendall in the MSU Library System for assistance and counsel to JTW in dealing with the vagaries of the EndNote algorithm.

The integrity of information and data interpretation contained herein has been bolstered by critiques from prominent colleagues in the field, including Professors Gavin Reid, John Allison, Jack Holland, Vernon Reinhold, Robert Brown, J.A. McCloskey, A. Daniel Jones, and Drs. Christian Rolando, J. Lemoine, Steven Pomerantz, Charles Ngowe, Chad Borges, Robin Hood, John Stults, and J. David Pinkston.

A special thanks to Professor Jean-Francois Gal, who generously provided lab/office space for JTW at the University of Nice for his sabbatical leave in 2002 during the formative stages of this project. The logical and systematic approach to presenting scientific/technical information that JTW learned from his mentor, Professor Klaus Biemann at MIT, was of continuing benefit during this project, and some of the critique/suggestions by Dr. Brian Sweetman and Professor John Oates at Vanderbilt University during preparation of the first edition of the book survive in this fourth edition. Thanks also to Patrick R. Jones, ODS’s colleague at the University of the Pacific, for great discussions and reflections especially on instrumentation and physical chemisty. We appreciate the counsel of Frederick E. Klink, who has been our co-instructor in short courses for the last 10 years, and who has greatly added to the portions of this book involving HPLC and LC/MS. We also appreciate the cooperation of Harold G. Walsh, Director of the ACS Short Course Program, during our tenure from 1978 to 2006 with his program, and to the thousands of students who have participated in these short courses as well as the instrument manufacturers who provided equipment and other support for our “hands-on” courses.

Special thanks go to Stephen E. Stein at the Mass Spectrometry Data Center of the National Institute of Standards and Technology for permission to use many of the EI mass spectra, which come from the NIST05 NIST/EPA/NIH Mass Spectral Database. Unless otherwise designated, spectra were taken from the NIST Mass Spectral Database. Also, the NIST Mass Spectral Search Program proved invaluable in the preparation of many of the non-EI mass spectra contained in this book.

Both authors offer a special thanks to ODS’s wife, Joan A. Sparkman, who spent a great number of hours implementing the suggestions of the Wiley contract-copyeditor and making sure that there was consistency throughout the book. Because of the sometimes orthogonally opposed styles of the authors, the inputs of the copyeditor and the proofreader, and further complications with the delivery of camera-ready copy, Joan has paraphrased the title of a song, saying that the style of this book can be considered “a little bit country, a little bit rock ‘n roll”. Thanks also goes to those two great canine mass spectrometrists, Maggie and Chili Sparkman, who endured the final edits with ODS and Joan.

“I feel sure that there are many problems in Chemistry which could be solved with far greater ease by the application of Positive Rays to chemical analysis than by any other method.”

~Joseph John Thomson

Chapter 1

Introduction

I. Introduction

1. The Tools and Data of Mass Spectrometry

2. The Concept of Mass Spectrometry

II. History

III. Some Important Terminology Used in Mass Spectrometry

1. Introduction

2. Ions

3. Peaks

4. Resolution and Resolving Power

IV. Applications

1. Example 1-1: Interpretation of Fragmentation Patterns (Mass Spectra) to Distinguish Positional Isomers

2. Example 1-2: Drug Overdose: Use of GC/MS to Identify a Drug Metabolite

3. Example 1-3: Verification that the Proper Derivative of the Compound of Interest Has Been Prepared

4. Example 1-4: Use of a CI Mass Spectrum to Complement an EI Mass Spectrum

5. Example 1-5: Use of Exact Mass Measurements to Identify Analytes According to Elemental Composition

6. Example 1-6: Is This Protein Phosphorylated? If So, Where?

7. Example 1-7: Clinical Diagnostic Tests Based on Quantitation of Stable Isotopes by Mass Spectrometry in Lieu of Radioactivity

V. The Need for Chromatography

VI. Closing Remarks

VII. Monographs on Mass Spectrometry Published Before 1970

Figure 1-1. This conceptual illustration of the mass spectrometer shows the major components of mass spectrometer, i.e., sample inlets (dependent on sample and ionization technique; ion source (origin of gas phase ions); m/z analyzer (portion of instrument responsible for separation of ions according to their individual m/z values); detector (generates the signals that are a recording of the m/z values and abundances of the ions); vacuum system (the components that remove molecules, thereby providing a collision-free path for the ions from the ion source to the detector); and the computer (coordinates the functions of the individual components and records and stores the data).

I. Introduction

Mass spectrometry is a microanalytical technique that can be used selectively to detect and determine the amount of a given analyte. Mass spectrometry is also used to determine the elemental composition and some aspects of the molecular structure of an analyte. These tasks are accomplished through the experimental measurement of the mass of gas-phase ions produced from molecules of an analyte. Unique features of mass spectrometry include its capacity for direct determination of the nominal mass (and in some cases, the molar mass) of an analyte, and to produce and detect fragments of the molecule that correspond to discrete groups of atoms of different elements that reveal structural features. Mass spectrometry has the capacity to generate more structural information per unit quantity of an analyte than can be determined by any other analytical technique.

Much of mass spectrometry concerns itself with the mass of the isotopes of the elements, not the atomic mass1 of the elements. The atomic mass of an element is the weighted average of the naturally occurring stable isotopes that comprise the element. Mass spectrometry does not directly determine mass; it determines the mass-to-charge ratio (m/z) of ions. More detailed explanations of atomic mass and mass-to-charge ratios follow in this chapter.

It is a fundamental requirement of mass spectrometry that the ions be in the gas phase before they can be separated according to their individual m/z values and detected. Prior to 1970, only analytes having significant vapor pressure were amenable to mass spectrometry because gas-phase ions could only be produced from gas-phase molecules by the techniques of electron ionization (EI) or chemical ionization (CI). Nonvolatile and thermally labile molecules were not amenable to these otherwise still-valuable gas-phase ionization techniques. EI (Chapter 6) and CI (Chapter 7) continue to play very important roles in the combined techniques of gas chromatography/mass spectrometry (GC/MS, Chapter 10) and liquid chromatography/mass spectrometry (LC/MS, Chapter 11). After 1970, the capabilities of mass spectrometry were expanded by the development of desorption/ionization (D/I) techniques, the generic process of generating gas-phase ions directly from a sample in the condensed phase. The first viable and widely accepted technique2 for D/I was fast atom bombardment (FAB), which required nanomoles of analyte to produce an interpretable mass spectrum. During the 1980s, electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) eclipsed FAB, in part because they required only picomoles of analyte for analysis. ESI and MALDI are mainly responsible for the dominant role of mass spectrometry in the biological sciences today because they are suitable for analysis of femtomole quantities of thermally labile and nonvolatile analytes; therefore, a chapter is devoted to each of these techniques (Chapters 8 and 9).

Mass spectrometry is not limited to analyses of organic molecules; it can be used for the detection of any element that can be ionized. For example, mass spectrometry can analyze silicon wafers to determine the presence of lead and iron, either of which can cause failure of a semiconductor for microprocessors; similarly, drinking water can be analyzed for arsenic, which may have health ramifications. Mass spectrometry is extensively used in geology and material sciences. Each of these two disciplines has developed unique analytical capabilities for the mass spectrometer: isotope ratio mass spectrometry (IRMS) in geology and secondary ion mass spectrometry (SIMS) in material sciences. Both of these techniques, along with the analysis of inorganic ions, are beyond the scope of this present book, which concentrates on the mass spectrometry of organic substances.