Mass Spectrometry: A Textbook Jürgen H. Gross Springer-Verlag, New York, 2004. $79.95 (518 pp.). ISBN 3-540-40739-1
Mass spectrometry is a diverse topic to learn and teach. The instruments are applied to a variety of analytical problems, ranging from elemental isotope separation to mapping the genome, the proteome (the set of proteins expressed by a cell or organ), and the metabolome (the metabolic products within a cell or organ). The technique is often the last in a long line of chemical or physical analyses. In other words, mass spectrometry is tailored to the research; it is the tail wagged by the dog.
Physics, chemistry, bio-chemistry, and all their various subdisciplines find their way into the general topic of mass spectrometry. Sorting out this diversity in a suitably pedagogic way is hardly trivial. Although monographs on various aspects of the subject are available, as are thousands of published papers regarding its applications to particular problems or sets of problems, no textbook existed, to my knowledge, that offered an integrated perspective. Even Jürgen Gross realized, as he states in his preface to Mass Spectrometry: A Textbook , that “the ideal textbook still seemed to be missing.” But maybe that statement is no longer true: Gross’s textbook comes close to the ideal.
Gross does two important things in his book. First, he admittedly focuses on organic mass spectrometry—which is by no means a shortcoming. In terms of samples analyzed and the diversity of analyses, organic mass spectrometry vastly overwhelms all other applications combined. Moreover, various aspects of it have direct applications to inorganic analyses.
The second important aspect of Gross’s work is that he organizes the text so that the fundamental and underlying elements of the field are discussed evenly and in detail in the first four chapters. Electron ionization and gas-phase ion chemistry are covered in the fifth and sixth chapters. The fundamentals are subsequently woven into discussions of various ionization methods. Anyone who would be a mass spectrometrist would do well to study the first six chapters in depth.
Chapters 7 through 11 can each be viewed as a standalone. The chapters are based on the principles of mass spectrometry addressed in the first five chapters, and each discusses a specific ionization method. Methods covered include chemical ionization, field ionization and desorption, fast-atom bombardment, matrix-assisted desorption and ionization, and electrospray ionization. The methods, in modern practice, result largely from bimolecular processes and lead to the formation of pseudomolecular ions, such as protonated molecules. The relative abundance of the ions, their fragments, and their adducts is the stuff of modern mass spectrometry. Yet each ionization method is different, characterized by its own protocols for sample preparation, loading, mass dispersion, mass spectral analysis, optimal instrumentation, and artifacts and pitfalls. Gross describes and contrasts the characteristics of each method clearly and in detail.
Gross’s consistent yet familiar and engaging style is educational, and the text is effectively integrated with graphics and diagrams—some 357, according to the title page. These photographs and diagrams address a range of topics, from tentatively identified compounds and reconstructed ion chromatograms, to fragmentation energetics, ion trajectories, and mass-spectrometer source design. The author uses well-placed, framed text-boxes to provide summaries, add technical and historical notes, address peculiarities, and give pointers. The approach is endearing, especially for students in the lab who would otherwise be left wondering why the mass spectrum did not turn out the way the book said it should.
Mass Spectrometry could easily serve as a laboratory handbook. Every chapter is exceptionally well documented, with up to 200 appropriate and current literature citations. To someone working in the field, such citations are invaluable. In addition, at the end of each chapter, Gross summarizes the effectiveness of each ionization method for compound class, polarity, and molecular weight. The book also contains what might be called anecdotal sections. For example, the brief section on buying an instrument is alone worth the price of the book. Although it is unlikely that a senior undergraduate or graduate student would be purchasing a mass spectrometer, timely reference to this section in a working laboratory would prevent any number of future headaches.
The final chapter, “Hyphenated Methods,” represents a paradigm shift. It is not about an ionization method at all but about combining separation with mass spectrometry. Coupling the gas chromatograph to the mass spectrometer was a monumental accomplishment 40 years ago. However, by the time a sample is run by gas chromatography–mass spectrometry (GC/MS), the mass spectrometry is pretty much a formality and chromatography becomes the main issue. Although the final chapter conveys the information necessary for a textbook, it lacks the enthusiasm generated by earlier chapters; that lack clearly reflects the fact that Gross is, after all, a mass spectrometrist, and subjects like GC/MS are fairly tame.
The book could have benefited from an expanded discussion of automated mass-spectral data handling, or perhaps even an added chapter. Mass spectrometers can generate data at a ferocious rate that necessitates automated methods, and the programs are commonplace. Currently, for example, there are at least 25 000 mass spectrometers that use automated search and retrieval systems for electrospray ionization spectra alone. Moreover, without automated analyses of mass spectra obtained from protein and DNA samples, the spectra would be practically useless: They simply contain too many peaks. Data retrieval and automated interpretation intrinsically fall into the domain of computer programming, but the programs were developed by mass spectrometrists using the very approach discussed in this book. In order for Gross to be consistent with the rest of the book, a discussion of the logic of these programs seems appropriate.
Taken as a whole, Mass Spectrometry is simply excellent. The book not only removes the label “black box” from the mass spectrometer but also conveys overall what might be termed as the central core of the philosophy of the mass spectrometrist. Many espouse the notion that mass spectrometry can be applied to analytical problems ranging from the obvious measurement of isotope ratios to the more subtle determination of the tertiary structure of proteins. If a problem isn’t solved, it simply isn’t solved yet. Scientists reading Gross’s book as students, teachers, or practitioners will understand why mass spectrometrists are so optimistic.
