Current trends: a perspective from 30 years of Atomic Spectrometry Updates

Atomic Spectrometry Updates (ASU) were incorporated into JAAS in 1986, but their history goes back to the late 1960s when the Atomic Spectroscopy Group of the Society for Analytical Chemistry, SAC (now part of the Analytical Division of the RSC) initiated a process to establish an annual publication to review the rapidly expanding field of atomic spectroscopy (http://www.asureviews.org/origins.php). This reached fruition in 1972, with the publication of the first of the Annual Reports in Analytical Atomic Spectroscopy (ARAAS). The historical development of ARAAS and ASU, the roles of the founders and their early aspirations are documented in a previous Editorial written for the 25^th Anniversary of JAAS.¹ Over the course of the last 30 years the Board of ASU has been populated by a changing roster of experts in the field of atomic spectrometry, including members from academia, industry and the public services. The ASU Editorial Board (Fig. 1) is an international organisation, with eight current members from outside the UK. There have been eight Chairs since Malcolm Cresser in 1986 – Doug Miles, 1989; Andy Ellis, 1995; John Marshall, 1998; Steve Hill, 2001; Phil Potts, 2005; Andrew Taylor, 2008; Hywel Evans, 2011 and currently Owen Butler, 2014 onwards.

Fig. 1 Some of the members of the ASU Board at their Annual Board Meeting in Hertfordshire on 2 July 2015. The members, starting at the foot of the steps, working up the steps and across the balcony, are: Mike Foulkes, James Murphy, Phil Potts, Jeff Bacon, Christine Davidson, Owen Butler, Bridget Gibson, Jorge Pisonero, Marina Patriarca, Raquel Garcia, Simon Branch (at top of steps), Martin Day, Andrew Taylor, Mike Sargent (in front), Andy Ellis (behind), Clare Smith, Margaret West, Steve Hill, Doug Miles, Robert Clough, Les Ebdon, Christine Vanhoof, Warren Cairns, Jenny Cook, Julian Tyson and Ian Whiteside.

The ASU operation comprises six separate reviews, which critically appraise advances that have taken place over the previous 12 months. They are published in alternate issues of JAAS: Environmental Analysis; Clinical and Biological Materials, Foods and Beverages; Atomic Spectrometry and Related Techniques; Elemental Speciation; X-ray Fluorescence Spectrometry; and Metals, Chemicals and Functional Materials. Each review is headed by a Topic Group Leader who assesses over 10 000 abstracts gleaned from the scientific literature over the preceding year. Selected abstracts are distributed to a team of writers who use their expertise in the field to decide what material to include. This process, from searching the literature and compiling a database, to selecting and distributing the material, writing and editing is handled completely in-house by members of the ASU Editorial Board. One of the unique aspects of ASU is the team of referees who oversee the quality of the reviews and suggest improvements in an annual cycle of overview and feedback. In addition, the annual Editorial Board Meetings provide an opportunity for an exchange of ideas between the six writing teams and ensure ongoing quality assurance.

A fundamental aspect of the ASU reviews is the critical appraisal of published research by experts to highlight developments and provide an easily accessible summary of the breaking trends in the field. The inbuilt continuity of the ASU Board lends a unique aspect to this process, such that new developments in atomic spectroscopy instrumentation and methodology are put into context, from initial conception to a level of maturity where they are widely applied. An obvious example is the development of inductively coupled plasma-mass spectrometry (ICP-MS) which, coupled with a variety of sample introduction methods, has now evolved into a pre-eminent technique for rapid multi-element and isotopic analysis in many fields, including clinical, geochemical, industrial and environmental applications. Space exploration, such as the recent missions to Mars and beyond, has stimulated research into techniques such as laser induced breakdown spectroscopy for direct, remote analysis of difficult samples. Similarly, improvements in portable X-ray fluorescence (XRF) instrumentation have resulted in its wide adoption by the mining industry to collect large amounts of multi-element data rapidly in the field, to the extent that it is now regarded by some exploration geologists as the modern equivalent of the geological hammer. In addition, developments and innovations in sample preparation and sample introduction methods have improved the speed and sensitivity of analysis, which has been of particular relevance to environmental testing laboratories that operate increasingly within commercial and legislative constraints.

The evolution of ICP-MS into a mature technique, allied with advances in sample preparation and separation, has led to new applications. The ease of coupling various chromatographic techniques, as a result of bespoke instrumental modifications and dedicated software for chromatographic peak integration, means that elemental speciation data are now readily accessible. The number of target analytes has increased from the more traditional species containing As, Hg, Pb, Se and Sn to ones incorporating almost any element, reflecting the importance of speciation information, particularly in water quality testing.

The drive to analyse ever smaller masses with superior spatial resolution has been a theme running through instrumental development since the earliest days of JAAS and ASU. Single particle analysis provides a means of quantifying engineered nano-particles be they derived from catalysts, drug delivery, vehicles, anti-microbial agents or sunscreens, and of assessing their impact in the wider environment. Characterisation of these materials or their suspensions has been achieved using field flow fractionation coupled with ICP-MS or, more simply, discrete single particle analysis using the high temporal resolution of this technique. This has enabled particle size distribution to be measured as well as analysis of purity. Spatial resolution using laser ablation (LA) coupled with ICP-MS now enables 2-dimensional mapping of clinical and geological samples; similarly high resolution depth analysis of surfaces and coatings can be achieved using glow discharge MS. Multi-collector (MC) ICP-MS is now becoming the method of choice for precise isotope ratio analysis. For example, LA coupled with MC-ICP-MS is a powerful technique for geochronological studies involving complex-zoned minerals or those requiring large datasets such as detrital mineral provenancing. When coupled with gas chromatography, compound-specific isotope ratio measurements can be used to elucidate pollutant pathways through ecosystems, to understand biotransformation mechanisms and determine pollutant sources. Another emerging technique is non-chromatographic speciation analysis, often in conjunction with miniaturised vaporisation, ionisation and detection systems. Further progress in this area could dramatically reduce instrumentation costs and lead to field deployment for continuous, temporal and spatial monitoring of target analytes in environmental testing regimes.

In the clinical field, innovations in sample preparation methods such as dispersive liquid–liquid micro-extraction have allowed the scaling down of preparative procedures in the trend towards ‘green’ chemistry. With improved analytical sensitivity new areas of investigation are being opened up, such as the release of metals like Co, Cr and Ti from metal implants. The wider development and use of reference materials, with concentration ranges for a large number of trace elements in biological fluids and tissues, has improved confidence in data; a good example being the speciation of As, Cr, Pb, Se, Sn in clinical samples, food and the environment, which has driven legislation. In a similar vein, the development of geochemical reference materials is also seen by many as an ongoing requirement in driving forward measurement confidence and comparability. The development of elemental and isotopically labelled conjugate molecules, DNA probes and intrinsically labelled biological molecules has facilitated the technique of elemental tagging for the relative and absolute quantification of biological molecules using ICP-MS. This rapidly expanding area has now advanced to the stage where it can be used as an assay technique at levels of detection suitable for clinical analysis.

Innovations in XRF instrumentation and techniques have also provided new ways of exploring the micro- and nano-world. Imaging techniques offered by μ-XRF facilities at synchrotron beamlines enable scientists to map subcellular metabolisms in animal and plant tissue. A hard XRF nano-probe with cryogenic capabilities has demonstrated improved spatial resolution and throughput for material systems including inorganic and organic photovoltaic systems, advanced batteries, fuel cell components, nano-electronic devices and advanced building materials. Analysis of nano-materials, particles and thin films have also benefited from advances in Total Reflection XRF and related techniques, whilst conventional laboratory-based systems embrace detector development from improved sensor array fabrication and readout devices. Non-destructive analysis is now essential for the examination of archaeological specimens, artwork, museum artefacts and forensic samples where sample preservation and integrity is paramount and is increasingly being used to probe the makeup of heterogeneous particles emitted in the atmosphere.

These developments in instrumentation and methods over the last 30 years have all been documented by the ASU Reviews. The ASU Editorial Board has evolved in terms of its operational procedures, focus of the reviews and composition of writing teams over this period. However, ASU's fundamental objective of providing a series of critically informed reviews reflecting advances in the changing world of atomic spectroscopy in 12 month cycles remains the same. As JAAS reflects on its scope and coverage² the ASU reviews will continue to adapt to meet the needs of readers.

References

1. S. Hill, J. Anal. At. Spectrom., 2010, 25, 1501–1502.
2. F. Vanhaecke, J. Anal. At. Spectrom., 2010, 25, 1015–1016.

---