Atomic spectrometry update. Atomic mass spectrometry

Abstract

This Update is part of a series of annual reviews which cover various aspects of analytical atomic spectrometry. This year’s review follows the same format as last year’s. Although an attempt is made to consider all relevant refereed papers, conference abstracts, reports, book chapters and patents for inclusion, the content of the review is highly selective. The selection of papers is based on criteria applied to focus sharply on the most significant developments in instrumentation and methodology or improved understanding of the fundamental phenomena involved in the MS process. The increasing importance of speciation and the blurring of boundaries between atomic and molecular MS require a high degree of judgement to be made in considering papers for inclusion. The main ruling criterion for all speciation papers is that the work should involve or be intended for the study of natural systems. For example, the study of synthetic metal clusters is generally not included, whereas the determination of organometallic compounds in environmental samples is.

Applications of atomic MS are not covered in this Update and readers are referred to the Updates on Industrial Analysis: Metals, Chemicals and Advanced Materials, Environmental Analysis and Clinical and Biological Materials, Food and Beverages. Other fundamental reviews appear on X-ray fluorescence spectrometry and atomic emission, absorption and fluorescence spectrometries.

Throughout this review, the term molecular ion will be restricted to denote only the positive or negative radical ion formed by removal or capture, respectively, of an electron. In contrast, addition of a proton or cation to a neutral molecule gives molecular adduct ions. Deprotonated molecules are considered as fragments.

Although reproducibility or precision is a key figure of merit in MS, there is no agreed format for quoting it. The reader can assume that values of precision given in this Update as a percentage correspond to the RSD unless otherwise specified. For isotope ratios, however, values of precision are generally given as the SD of a permil value.

It is a widespread phenomenon that analytical techniques in general, and MS in particular, spawn a large number of abbreviations and acronyms. A glossary of all abbreviations used in this Update appears at the end of the review. Most abbreviations are not defined in the text but those which are unlikely to be commonly known are defined in the text when used first and again in the glossary.

The developments highlighted in this review indicate the very wide area of applications for which atomic MS can be used. From the measurement of very low isotopic abundances to the measurement of element concentrations at any scale, from bulk analysis to depth profiling and localized analysis, there is likely to be an MS procedure which can provide analytical performance competitive with any other technique. The excellent review by Lobinski et al. on the use of MS in bioinorganic analytical chemistry discussed recent developments in ESMS, ICP-MS and MALDI-MS for metal speciation analysis and provided numerous examples of applications to environmental, plant, animal and medical studies. Reviews on the speciation of As and Hg in environmental samples included MS detection within a wider consideration of all aspects of the analysis. An extensive review of iron isotope measurements and applications showed that while the processes that govern iron isotope variations in nature are just beginning to be understood, it is clear that the system has direct relevance to important problems in geosciences and biology. The field is developing rapidly with applications to geochemistry, cosmochemistry and biochemistry. The various sections of the review covered Fe isotope nucleosynthesis, sample preparation and analysis by SIMS, RIMS, TIMS and MC-ICP-MS, and Fe isotope behaviour in a wide range of environments, both extraterrestrial and terrestrial (low temperature aqueous and biological systems, and high temperature systems).