Steve J. Hill

This is the 18th Atomic Spectrometry Update (ASU) to focus on advances in elemental speciation and covers a period of approximately 12 months from January 2025. This ASU review deals with all aspects of 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. As with all ASU reviews, the focus of the research reviewed includes those methods that incorporate atomic spectrometry as the measurement technique, although molecular detection techniques are also included where they have provided a complementary approach to speciation analysis. The number of publications covered this year has fallen to the lowest number since this ASU has been published. However, there is still a good breadth of elements covered, with the most popular elements still being As, Hg and Se, and the focus of many papers is on elucidating mechanisms and transformation pathways, particularly in plants and animals/humans, rather than concentrating on the speciation method. A number of papers covering speciation analyses of elements related to nuclear power generation have been published, which reflects the increasing demand for this power source in the global efforts to decarbonise. There has also been a report on the use of XRF spectroscopy as a detector for LC and three papers of note that describe comprehensive methods for metallobiomolecules. Once again, the quality of the abstract for many of the papers is poor, with detail on the methodology, key results with data included, conclusions and implications thereof missing. This is likely to lead to fewer researchers reading the article or considering it for reviews such as those produced by the ASU.

This review covers advances in the analysis of advanced materials, metals, fuels and lubricants, nanostructures, ceramics, refractories, organic and inorganic chemicals, catalysts and nuclear materials by a range of techniques including X-ray, ICP, LIBS, mass spectrometry, synchrotron-based techniques, plus non-destructive and ablation surface techniques.

This is the 17th Atomic Spectrometry Update (ASU) to focus on advances in elemental speciation and covers a period of approximately 12 months from January 2024. This ASU review deals with all aspects of 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. As with all ASU reviews, the focus of the research reviewed includes those methods that incorporate atomic spectrometry as the measurement technique, although molecular detection techniques are also included where they have provided a complementary approach to speciation analysis. The number of publications covered this year has increased since last year but remains relatively low compared to many of the years that this ASU has been published for. However, there is a good breadth of elements covered, with the most popular elements still being As, Hg and Se, although there is little novelty in the analytical approaches employed, which reflects the maturity of elemental speciation analysis, and over 25 elements are covered in total, including a growing number of papers covering essential macro and trace elements, such as Fe and Mn and P, and S as a heteroatom in proteins. The advent of ICP-MS/MS instrumentation, allowing for the cost-effective quantification of S as SO at m/z 48, thus negating the ¹⁶O₂ interference is probably behind the rise in papers on this element once again, the quality of the abstract for many of the papers is poor, with details on the methodology, key results with data included, conclusions and implications thereof missing. This is likely to lead to fewer researchers reading the article or considering it for reviews such as those produced by the ASU.

This is the 16th Atomic Spectrometry Update (ASU) to focus on advances in elemental speciation and covers a period of approximately 12 months from January 2023. 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. 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. The number of publications covered this year has increased since last year but remains relatively low compared to many of the years that this ASU has been published for. However, there is a good breadth of elements covered, over 20 this year, with the most popular elements still being As, Hg and Se whilst Ge and Tc both make their first appearances this year. Another item to note is the decreasing quality of the abstract for many of the papers, with detail on the methodology, key results with data included, conclusions and implications thereof missing. This is likely to lead to fewer researchers reading the article.

This is the 15^th Atomic Spectrometry Update (ASU) to focus on advances in elemental speciation and covers a period of approximately 12 months from January 2022. 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. 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. This year the number of publications covered has fallen again along with the number of elements covered, most likely due to effects of the Covid-19 pandemic restricting laboratory access. The most popular elements remain as As, Hg and Se and the range of matrices under study is still broad with biological, environmental and foods being the most popular.

This is the 14^th Atomic Spectrometry Update (ASU) to focus on advances in elemental speciation and covers a period of approximately 12 months from December 2020. This ASU 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. As with all ASUs, 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. This year, the number of publications covered has fallen, quite possibly due to the SARS-CoV-2 pandemic restricting laboratory access, but the number of elements covered remains high at over 30. The most popular elements are still As, Hg and Se, whilst more workers are using some form of separation to reduce the dissolved ion signal when undertaking analysis for NPs. There has also been an increase in the number of papers reporting on field deployable miniaturised devices for elemental speciation, a trend which will surely continue as the associated technologies develop more robust and less power hungry portable excitation sources.

This is the 13^th Atomic Spectrometry Update (ASU) to focus on advances in elemental speciation and covers a period of approximately 12 months from December 2019. 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. 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. This year the number of publications concerning As speciation remains similar to those covered last year, as do those for studies on Se speciation. The recent growth in work concerning Hg speciation has halted, although this is still a popular topic with the number of reports concerning Fe, halogen and sulfur speciation also rising. The number of elements covered this year reaches 30, showing the breadth of the elemental speciation field and how such work is now becoming more routine.

The transport of arsenic from soil through to edible crop is important when assessing the potential health risks from a food source. Samples of soil, irrigation water and the rice plant, Oryza sativa, were collected from an agricultural site in the Middle East. Total As, its speciation and DNA fractionation were evaluated using HPLC-ICP-MS in samples which included the root, stem, leaf and grain of the rice plant. Methodology was validated through the use of CRMs. The highest concentration of As was found in the root of the plant and the lowest in the grain. The concentrations found for As were: soil (aqua-regia extractable; 2.88 μg g⁻¹), irrigation water (0.58 μg L⁻¹), roots (8.28 μg g⁻¹), stem (4.00 μg g⁻¹), leaves (2.93 μg g⁻¹) and grain (1.02 μg g⁻¹). Levels of inorganic As^V and As^III were identified in the soil and plant material, while organo-arsenic species (DMA, MMA) were below the limit of detection. The ‘plant available’ levels of As in the soil (14%) were determined as part of a full, validated BCR three-step sequential extraction procedure. Since As can behave as a phosphate analogue, a method was developed for the extraction of vegetative DNA to determine the different forms of As associated with, or integrated within, the DNA fractions. Measurement of As in the DNA extracts were above the LOD (0.019 μg kg⁻¹) for the root, stem and leaf samples. The concentration of both weakly and strongly associated As with DNA obtained from the root, stem and leaf decreased with decreasing total As concentrations. A narrow, near-constant ratio for the strongly associated As value (As/total As DNA) in all root, stem and leaf DNA samples (41.3 ± 0.3%) was further evidence for the incorporation of As into the DNA.

This is the 12^th Atomic Spectrometry Update (ASU) to focus on advances in elemental speciation and covers a period of approximately 12 months from December 2018. 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. 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. This year the number of publications concerning As speciation has fallen by about half, as have studies on Se speciation. Growth areas continue to be Hg and ‘biomolecules’, with the number of reports concerning halogen and sulfur speciation also rising. The number of elements covered this year is again over 20, showing the breadth of the elemental speciation field.

This is the 11^th Atomic Spectrometry Update (ASU) to focus on advances in elemental speciation and covers a period of approximately 12 months from December 2017. 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. Therefore, 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 the speciation analysis of over 20 elements reported this year.