Inorganic mass spectrometry (inorganic MS) has had an important presence in chemical analysis for many years and much has been written, especially since the adoption of inductively coupled plasma mass spectrometry, ICPMS, on a routine basis. Hence the clear need for a comprehensive look at this field in a manner readily understandable with benefit for novice or expert. Dr J. Sabine Becker has risen to this challenge and produced an excellent book that gives a unique perspective through its broad coverage of the field by reviewing the important aspects of it, as we know it today. The reader will find excellent coverage of sample preparation, sample introduction, ion sources, ion separation, ion detection and an extensive illustration of applications. It is further strengthened by the exceptionally high number of references. The writing is clear and concise and even the novice can come to a working level in the subject without having to search external references, or having to wade through heavy mathematical arguments. A very important plus with this offering is that it is a one-author book and offers a coherence of thought and style that no multi-authored work can achieve. Thus as one progresses through Dr Becker’s chapters, it is more like moving through a good textbook than a series of review chapters. Beyond major libraries, this offering is well suited for a graduate course in inorganic mass spectrometry.
The introductory chapter is brief but provides an ample introduction to mass spectrometry and leaves one comfortable as he/she moves on to the historical and instrumentation chapters that follow. A few of the basic equations are given as part of the review of basic concepts. In these few pages Dr Becker clearly introduces the concepts of atomic mass units relative to carbon, isotopes and isotope abundance. Figures 1.1 and 1.2 go hand in hand in providing the reader with the three major parts of a mass spectrometer (source, ion separation, detection) and show various alternatives for each of these. The subtle use of color in these and subsequent figures adds an attractive benefit for the reader.
Chapter 1 goes into some nicely done historical detail. This chapter begins in the late 19th century and traces those developments through the years. The numerous figures and pictures show well some of the early ingenuity of those exceptional scientists and Dr Becker is careful to note the importance assigned to mass spectrometry by the scientific community of that time; one measure being the numerous Nobel prizes awarded. The history as she presents it provides an excellent
context for the future and current developments that this work highlights. Of particular interest to this reader are the early discussions about Wien, Aston and Thompson.
Chapter 2 highlights ion sources for inorganic mass spectrometry and given its popularity, it is no surprise that the inductively coupled plasma (ICP) receives the most attention. Noteworthy here are Figures 2.1 and 2.2, which provide informative summaries regarding atomization and ionization processes leading to the atomic ion followed by an excellent discussion of the ICP highlighting its operation and discussing solution nebulization for sample introduction. The reader will also find optimization discussion and figures – for example, fraction of ionization in the plasma. After the primary discussion of the ICP as an ion source, Figure 2.12 summarizes the various sample introduction modes associated with the ICP and does so in an easily visualized fashion. Dr Becker continues with discussions on selected sample introduction methods to the ICP including laser ablation, electrothermal vaporization, and hydride generation. This is followed by other sources; namely, spark ion source, laser ion source, glow discharge ion source, thermal surface ion source (TIMS – Figure 2.28 shows elements available), SIMS, and SNMS. Following these, softer ion sources for fragmentation and molecular ion formation; namely, electron ionization, MALDI and ESI are briefly discussed. Table 2.2 provides an excellent comparative summary of the various ion sources.
Chapter 3 continues Dr Becker’s excellent presentation and has ion separation as its focus. The chapter begins with well developed text on electric and magnetic field sectors for ion separation and culminates with the combination of both sectors – double focusing ion separation as the most important of the three sector possibilities for high resolution inorganic mass spectrometry. However, the quadrupole mass filter is clearly the most widely used and often sold commercially available ion separation system and therefore, appears prominently in the text. This is followed by the time-of-flight (TOF), which has the ability to take spectra very fast and therefore should be highly amenable to laser ablation, chromatography and other sample introduction methods where a transient sample pulse passes through the ion separator. Two other ion separation methods are discussed in this chapter; ion-trap technology and FTICR (fast Fourier transform ion cyclotron resonance), although these are most widely used for molecular MS. The last part of the chapter reviews the concepts of resolution and abundance sensitivity – important to ICPMS users for any of the three commercially available inorganic MS types.
Chapter 4. Ion detectors are the last of the three major mass spectrometer components. With a particular focus on inorganic MS, a concise and well-written chapter results. Dr Becker begins with a discussion of the classical Faraday cup detector, which in its current configurations are still in use today. The secondary electron multiplier (SEM) is introduced and the explanation is readily understandable to the novice through a carefully designed Figure 4.2. It becomes apparent the electron multiplication is the best choice for low-level signals. She draws attention to the SEM in the dual ion mode for either the analog or pulse counting. For extended dynamic range the combination of Faraday cup and SEM is discussed with high ion current channeled to the Faraday detector and low ion currents to the SEM. The channel electron multiplier (CEM or channeltron) and microchannel plates are the next topics. The CEM is shown in Figure 4.5 in both the analog and pulse counting mode. As a modern alternative to the Faraday cup is the Daly detector (Fig.
4.6). This short chapter finishes with multi-collector devices for true simultaneous multi-element analyses.
When ion sources, ion separation and detection are combined, a mass spectrometer system results. While some choose to build their own, a wide variety of these are commercially available, offering as wide a combination of sources, separation means and detection. Chapter 5 focuses on these systems and is given the general title of “Instrumentation.” For inorganic MS, Figure 5.1 and 5.2 illustrate some possible combinations by adding sample introduction to ion sources andseparation (the detector is implied). Initially the discussion involves the quadrupole as the ion selector, since it is the most widely used with ICPMS. Collision/reaction cells are also brought into the discussion highlighting the additional power ICPMS has for detection through non-metal and some metal ions. Table 5.1 compares four different ICPMS quadrupole products. The plasma source ion trap is also discussed followed by ion separation using a double focusing sector field instrument with a single detector. Time-of-flight instrumentation is then carefully reviewed and Figure 5.10 illustrates a recent market introduction. Multi-detector (named multicollector) sector field instruments make up the next portion of the chapter and figures of merit for sector field instruments are compared in Table 5.2. Solution sample introduction via nebulization, hydride generation and flow injection are the next topics plus hyphenated methods are touched on here. As an important topic, Laser Ablation ICPMS is included in Chapter 5. At this point Dr Becker departs from ICPMS as the source to a number of other inorganic MS systems, of which Glow Discharge may be the most important today. Overall the discussion provides an excellent overview of the types of instrumentation useful for inorganic mass spectrometry.
Chapter 6 begins the discussion on analytical and practical considerations regarding the use of inorganic MS. Qualitative use of the techniques point out salient issues that need to be considered such as isotope pattern, mass determination and interference problems, which are well illustrated in the accompanying figures. Lengthy discussion is given to quantitative approaches and, as might be expected, internal standards, standard addition and isotope dilution get a lot of attention. Although not in method detail, the analyst can benefit highly from the discussion, which presents good “how to” ideas. Beyond solution sample introduction follows laser ablation for solids. An important focus here is the topic of calibration for quantitative determination by laser ablation. Next the reader will find an often ignored or minimized aspect of the analysis – sample preparation. The chapter is easy reading, but of high importance.
Gaseous and volatile compound analysis is covered in Chapter 7. Since all MS systems ultimately require gas phase ions, such a topic is of high importance in inorganic as well as molecular MS analysis. The chapter is short, yet does cover sample preparation for volatiles as well as some important applications. This chapter is very well referenced.
Chapter 8 addresses one of the most important features of inorganic MS – isotope ratio or isotope abundance measurements. As part of a brief introduction, Figure 8.1 provides a good departure for applications of isotope ratio measurements. The discussion provides insights to the capabilities of inorganic MS for isotope ratio measurements, mass discrimination effects, isotope ratio measurements by various types of MS. Table 8.4 gives some interesting applications of isotope ratio measurements. Multicollector ICPMS is discussed for precise isotope ratios and this section is followed by isotope dilution measurements. The chapter concludes with a focus on long-lived radionuclides, geochemistry and geochronology. As is Dr Becker’s pattern, the reference section is very well done.
Chapter 9 is a major offering in fields of inorganic MS. At 205 pages, it details applications of inorganic MS for trace, ultratrace and surface analysis. Indeed, no forward can do justice to this exceptional review of applied inorganic MS, nor with space limitations adequately describe it. Notable however, is the richness of figures and tables drawing together from many resources comparative information along and across the various inorganic MS methods and their unique strengths and weaknesses. In fact, the reader will find 46 tables, 67 figures and 12 reference sections included in Chapter 9. The various MS methods and their numerous applications to a variety of sample types require an exhaustive search and clearly this was done for this book chapter (e.g. Ref. Section I alone has 159 references). Applications include materials science, environmental science and control, biology, bioengineering, medicine, foods, geology and geochemistry, cosmochemistryand space science, long lived radionuclides, forensic applications, and additional further applications. Dr Becker also devotes a section of this chapter to a very important aspect of inorganic MS, polyatomic ion formation. All-in-all this chapter provides either the novice or expert an excellent overview on up-to date applications of these powerful MS techniques.
Chapter 10 briefly addresses future trends as Dr Becker sees them emerging. She looks to higher resolution mass spectrometers for better interference separation, better sensitivity and lower detection limits. With this enhanced analytical power she also predicts increased user friendliness, better isotope ratio measurements, smaller sample sizes, enhanced capability to handle transient signals and further advances in sample introduction.
Ultimately the reader will find this work an excellent addition to their library. As earlier indicated, the text reads well, is crisp and concise and provides excellent up-to-date coverage of inorganic mass spectrometry and the important ancillary topics.
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