Atomic spectrometry update: Elemental speciation

This is the second Atomic Spectrometry Update (ASU) to focus specifically on developments in elemental speciation and covers a period of approximately 14 months from November 2008. The International Union for Pure and Applied Chemistry (IUPAC) have evaluated speciation and provided a definition: speciation analysis is the analytical activity of identifying and/or measuring the quantities of one or more individual chemical species in a sample; the chemical species are specific forms of an element defined as to isotopic composition, electronic or oxidation state, and/or complex or molecular structure; the speciation of an element is the distribution of an element amongst defined chemical species in a system. This review will therefore deal with all aspects of the analytical speciation methods developed for: the determination of oxidation states; organometallic compounds; coordination compounds; metal and heteroatom-containing biomolecules, including metalloproteins, proteins, peptides and amino acids; and the use of metal-tagging to facilitate detection via atomic spectrometry. The review will not specifically deal with operationally defined speciation, but will highlight other reviews which cover the work in this area. As with all ASU reviews, the coverage of the topic is confined to those methods that incorporate atomic spectrometry as the measurement technique, but molecular methods are also included in this review where appropriate. Clearly by their nature some speciation methods will involve the determination of molecular structure and there is an increasing trend for this type of approach, as is highlighted in the current review. As the contents of this Update show, there is considerable activity in the development and application of methods of elemental speciation analysis, which for some elements and combinations of techniques is a mature field as shown by the extent to which relevant topics have been the subject of review articles. Activity in the area of new instrumental hardware specifically developed to meet the twin needs of quantitation at low concentration, in parallel with species identification, is a noteworthy development during this review period. Other strong areas of interest continue to focus on the speciation analysis of As, Cr, Hg, Se and Sn.