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This is the tenth Atomic Spectrometry Update (ASU) to focus on advances in elemental speciation and covers a period of approximately 12 months from December 2016. This ASU review deals with all aspects of the analytical atomic spectrometry 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 does not cover fractionation, which is sometimes termed operationally defined speciation. As with all ASU reviews the focus of the research reviewed includes those methods that incorporate atomic spectrometry as the measurement technique. However, because speciation analysis is inherently focused on the relationship between the metal(loid) atom and the organic moiety it is bound to, or incorporated within, atomic spectrometry alone cannot be the sole analytical approach of interest. For this reason molecular detection techniques are also included where they have provided a complementary approach to speciation analysis. As in previous years, As speciation continues to dominate the current literature with a significant number of publications concerning Hg and Se speciation and ‘biomolecules’, in which category a number of papers covered in the Se section could also belong. The number of elements covered in these updates also continues to rise with speciation analysis of over 20 elements reported this year. [ABSTRACT FROM AUTHOR]

In this paper the reactivity of K15H[Zr(α2-P2W17O61)2]·25H2O (1), a Zr(iv)-substituted Wells–Dawson polyoxometalate, is examined towards a series of Gly–Aa, Aa–Gly or Aa–Ser dipeptides, in which the nature and the size of the Aa amino acid side chain were varied. The rate of peptide bond hydrolysis, determined by 1H NMR experiments, in Gly–Aa dipeptides is strongly dependent on the molecular volume and the chemical structure of the Aa side chain. When the volume of the aliphatic side chain of the Aa residue in Gly–Aa increased, a clear decrease in the hydrolysis rate was observed. Replacing one α-H in the C-terminal Gly residue of Gly–Gly by a methyl group (Gly–Ala) resulted in a 6-fold reactivity decrease, pointing towards the importance of steric factors for efficient peptide bond hydrolysis. The rate constants for peptide bond hydrolysis in Gly–Aa dipeptides at pD 5.0 and 60 °C ranged from 208.0 ± 15.6 × 10−6 min−1 for Gly–Ser to 5.0 ± 1.0 × 10−6 min−1 for Gly–Glu, reflecting the influence of the different nature of the amino acid side chains on the hydrolysis rate. Faster hydrolysis was observed for peptides containing Ser and Thr since the hydroxyl group in their side chain is able to facilitate amide bond hydrolysis by promoting an N→O acyl rearrangement. Peptides containing positively charged side chains at pD 5.0 show enhanced hydrolysis rates as a result of the secondary electrostatic interactions with the negatively charged surface of the polyoxometalate, which stabilize the peptide–polyoxometalate complex. A slow hydrolysis rate was observed for Gly–Glu, because of the preferential coordination of the carboxylate group in the side chain of Glu to Zr(iv), which prevents coordination of the peptide carbonyl group and its activation towards hydrolysis. [ABSTRACT FROM AUTHOR]