Book reviews
Elemental Speciation. New Approaches For Trace Element Analysis Edited by J. A. Caruso, K. L. Sutton and K. L. Ackley. Volume XXXIII in Wilson and Wilson's Comprehensive Analytical Chemistry. Series Editor D. Barcelo. Pp. 612. Elsevier. 2000. Price $288.00. ISBN 0444500472. Search PubMedThe 33rd volume in Wilson and Wilson's series on comprehensive analytical chemistry deals with elemental speciation. This subject is treated on 581 pages, divided into fifteen chapters written by altogether 30 distinguished authors. The state of the art and future directions for elemental speciation are summarized together with approximately 1200 unique references for additional in-depth information.
The fifteen chapters describe the following topics: (chapter 1) Introduction; (chapter 2) Sample preparation; (chapter 3) Biological substrates for pre-concentration and element speciation; (chapter 4) LC chromatographic techniques for trace element speciation analysis; (chapter 5) GC and SFC techniques for elemental speciation; (chapter 6) CE for elemental speciation studies; (chapter 7) Nebulizer sample introduction for elemental speciation; (chapter 8) The use of ICP-AES for elemental speciation studies; (chapter 9) The use of ICP-MS for elemental speciation studies; (chapter 10) Application of isotope dilution in elemental speciation: speciated isotope dilution mass spectrometry (SIDMS); (chapter 11) Plasma sources as alternatives to the atmospheric pressure ICP for speciation studies; (chapter 12) Electrospray ionization MS; (chapter 13) Trends in speciation analysis for routine and new environmental issues; (chapter 14) Speciation analysis of biological, clinical and nutritional samples using plasma spectrometry; (chapter 15) Certified reference materials: a tool for quality control of elemental speciation analysis.
In general the book is well written, comprehensive and very useful for anyone who wants to commence speciation work or widen the scope of their speciation studies. It is inevitable that there is some overlap of topics because certain facts may be found in more than one chapter. There are also some minor errors in that two figures should change place and misspelling of references here and there. These flaws are irrelevant since the overall assessment must be that this book is a very welcome contribution to the analytical community. The reader should at least be of graduate or postgraduate level as with all kind of specialized literature.
As can be seen operationally defined speciation methods, such as sequential extraction schemes and electrochemical techniques ( i.e., ASV, sensors and ISE), are omitted. This is probably in line with the future direction in speciation analysis since it is desirable to reach the same kind of specificity found in, for example, environmental PCB analysis. All chapters are worth studying in detail but some are possibly more interesting. I would like to point out chapters 2, 3, 6 and 10–14. Herein areas that have been lagging behind the instrumental boom during the last decade are described, such as sampling, sample pretreatment, and alternatives or complementary techniques to the mainstream HPLC-ICP-MS. In my opinion, chapters 11 and 12 deserve special attention by those who want to perform state of the art speciation in the future.
Chapter 10 describes speciated isotope dilution mass spectrometry (SIDMS). This rather new direction in speciation has received a fair amount of attention because it provides a tool to assess species conversion, i.e., species breakdown or alteration. The species of interest is synthesized and enriched with a stable isotope. By measuring the isotope ratio following chromatographic separation one can evaluate the fate of this particular chemical form of an element. The forward and backward rate of equilibrium can be monitored, giving the net rate of formation of a certain species if more than one stable isotope can be used (as exemplified for chromium in chapter 10). Moreover, one or more specific steps in a multi-step sample preparation procedure can be evaluated whether they are causing species alteration or not. Obviously there are some restrictions since not all elements have two or more stable isotopes. Nonetheless, I will cite a particularly important paragraph in this chapter to illustrate the importance of the SIDMS methodology: “The quality assurance of speciation methods has lacked such an evaluation and validation tool impeding the propagation and legal acceptance of data based on speciated evaluations”.
Certified reference materials for speciation are of course also very important and useful for this purpose. In the future it is likely that the methods used for certification must be shown to be free of artifact formation and/or analyte breakdown using SIDMS protocols before results can be accepted, in addition to the strict demands stipulated today as outlined in chapter 15.
The most comprehensive chapter in this book is the one on Electrospray ionization MS (chapter 12). I find this very useful because I believe that most researchers involved in speciation have a background in inorganic analytical chemistry and are much more familiar with techniques such as AAS, ICP-AES and ICP-MS. Although most authors in this book recommend chromatography coupled to ICP-MS as the best tool for speciation studies they recognize that molecular information from the species of interest is lost using this technique. There is thus a need for complementary information from a sensitive technique that is capable of providing molecular and structural information. Without such a technique a paradox occurs in that an “unknown” species has to be known a priori since positive species identification relies on retention time and element specific signal from the detector. To this end electrospray ionization MS is probably the most suitable technique and has received increasing attention for speciation studies during the last five–seven years, although it is not as sensitive as ICP-MS. In the future it is possible that we will see hybrid instruments that provide ESI-MS spectra and elemental ICP-MS spectra in a parallel fashion following a chromatographic separation. This kind of instrument, together with SIDMS protocols, will certainly improve the reliability and accuracy of results obtained in speciation studies in comparison with what we accept today.
Håkan Emteborg
Instituto Geologico y Minero de Espana, 28760, Tres Cantos, Madrid, Spain
Plasma Source Mass Spectrometry—The New Millennium Edited by Grenville Holland and Scott D. Tanner. Pp. 400. The Royal Society of Chemistry. 2001. Price: £69.50. ISBN 0854048952. Search PubMedThis book is a collection of papers presented at the 7th International Conference on Plasma Source Mass Spectrometry in Durham, 2000. As the title indicates this is also a book that pictures plasma source mass spectrometry at the beginning of the new millennium, and the book does that well covering topics that are ‘hot’ right now. The papers are presented in six sections: “Sample Preparation and Introduction”, “Mass Analyser Instrumentation”, “Reaction Cells for ICP-MS”, “Applications”, “Isotope Ratio Measurement” and “Speciation”. As such, the book is an excellent supplement to more traditional textbooks on plasma source mass spectrometry, covering in detail topics like reaction cell and time-of-flight ICP-MS, topics that are not covered in such detail in traditional textbooks.
Another topic covered by this book, although not as a separate section, is the use of uncertainty budgets. Several papers deal with this important tool to characterize, evaluate and optimize analytical methods. It is interesting to note how calculation of uncertainty on analytical results is slowly becoming an integral part of plasma source plasma spectrometry, probably due to the fact that plasma source spectrometry is now used for many routine applications where estimation and determination of uncertainty are required.
In general, the papers are written in an informal language and the authors have been given more freedom to discuss and justify their research than is usually allowed in most analytical journals. This is refreshing and makes the papers easier and more interesting to read. It furthermore allows the authors to include detail that would otherwise have been left out.
The books contain many good papers, but the four papers in the section “Reaction Cells for ICP-MS” are especially interesting and together they provide a good basis for understanding the theory behind the reaction cell technology. Another related paper on Inductively Coupled Plasma-Ion Trap Mass Spectrometry by Furuta et al. shows that this technique, like reaction cell ICP-MS, can be used for interference-free determination of Se-80, Ar 2+ being separated from the 80Se + in the ion trap. This instrument is commercially available in Japan and might in the future become a true alternative to reaction cell ICP-MS.
Eight papers have been included in the speciation section, covering both liquid chromatography-ICP-MS and gas chromatography-ICP-MS. The paper by Feldman el al. is an excellent example on the use of speciation analysis to provide new information on the metabolic pathways of arsenic compounds. The special Orkney Island sheep, from which the samples were taken, eat 3 kg of seaweed daily, which equals a daily uptake of 50 mg of arsenic, mainly as arsenosugars. Feldman et al. show that the sheep excrete the arsenic as dimethylarsinic acid, a finding they use to propose pathways for the metabolism of arsenosugars in a mammalian organism.
The first paper in the section on “Applications” is by Prohaska et al. entitled “Application and Quality in ICP-MS Analysis”. This paper provides a good and interesting summary on the history of mass spectrometry and ICP-MS, starting with J. J. Thomson building the first mass spectrometer at the beginning of the 20th century. This summary makes one realize the tremendous progress we have witnessed in the field of mass spectrometry during last 100 years, from the discovery of atoms plus isotopes and the acquisition of the first mass spectrum to mass spectrometric measurements being routine in many laboratories all over the world. What the next 100 years will bring, we can only guess about.
Stefan Stürup
Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire, USA
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