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Abstract: This ASU review focuses on developments in applications of atomic spectrometry to the characterisation of metals, chemicals and functional materials. While each of these application categories is very distinct in terms of the analytical challenges posed, there are a number of common themes than can be identified from an examination of the relevant literature appearing over the review period. The traditional atomic spectrometry techniques (e.g. AAS, OES, XRF, ICP-MS) are relatively mature, but reports continue to appear that seek to address perceived limitations in sensitivity in certain applications, but increasingly more frequently in relation to sample handling and preparation/extraction methodologies, validation and creation of SRMs and methods. However, it is equally clear that because of that very maturity such techniques are more often cited as analytical reference methods to support the development of other approaches (e.g. GD-OES, GD-MS, PIXE, PIGE, RBS, SEM-EDS, SIMS, TXRF, micro- and macro-XRF, XAS, XPS) that provide either direct sampling or depth and lateral elemental profiling capabilities. Consequently, a variety of techniques may now be routinely applied within an individual study to characterise samples to the extent it is hard to comment critically on the particular analytical novelty that lies at the heart of the work. It is fair to say that in some cases, the significance of the research now involves revealing the features of the sample (including examining surface modifications, coatings, thin films and multilayers, or even the characteristics of a device, functional component, or object, or complex mixture) rather than in the development of the analytical approach itself. That said, certain trends in technique development still expand the range of applications that can be addressed. For example, interest in LIBS continues to command attention and is heavily cited in most application sections of this review. The technique offers certain unique advantage for elemental analysis in rapid direct sampling, portability and operating in remote and harsh environments (including industrial production) where low level detection is not essential. Clearly sensitivity remains the Achilles' heel for LIBS but developments in measurement technique such as pulse delay are resulting in better optimised procedures. The development in laser solid sampling technology is providing benefits applicable to other techniques such as ICP-MS and newer variants such as laser ionisation MS. Indeed, lasers, flames, plasmas and other electrical discharges have been used regularly in the fabrication of samples. The atomic spectrometry techniques with which they have been associated are now employed to study such production processes in situ. The development of nanomaterials has given rise to new approaches to particle size distribution and single particle characterisation where the atomic spectrometric determination produces a size rather than a concentration. There is evidence too in the review of research work going on to understand the environmental consequences of the widespread use of new technologies using data analysis approaches to examine source, provenance or impact. Consequently, while the fundamental analytical questions: “What?” and “How much?” continue to be relevant to researchers increasingly these must now be qualified in many situations by providing answers to enquiries such as “Where?” and “How big (or small)?”.

Open Access

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Abstract: With the development of fourth-generation high-brightness synchrotrons on the horizon, the already large volume of data that will be collected on imaging and mapping beamlines is set to increase by orders of magnitude. As such, an easy and accessible way of dealing with such large datasets as quickly as possible is required in order to be able to address the core scientific problems during the experimental data collection. Savu is an accessible and flexible big data processing framework that is able to deal with both the variety and the volume of data of multimodal and multidimensional scientific datasets output such as those from chemical tomography experiments on the I18 microfocus scanning beamline at Diamond Light Source.

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Abstract: We present Ba L3-X-ray Absorption Fine Structure (XAFS) data from a suite of barium carbonates (witherite, alstonite, barytocalcite), hydroxides, sulfate(vi) (barite) and a Ba-bearing organic compound to explore whether Ba L3-XAFS could be used to fingerprint structural states in biominerals such as celestite, aragonite and calcite. Although there is a general similarity between all X-ray Absorption Near Edge Structure (XANES), subtle differences are observed in detail, which allow almost all phases to be distinguished. The XANES are considered as composites of four components, termed ‘A’ (5255 eV), ‘B’ (5258 eV), ‘C’ (5268 eV) and ‘D’ (5273 eV). ‘A’ is observed in barium hydroxides and most visible in the first derivatives of the XANES data. The minimum after the Ba L3 white line lies at 5257 eV for most materials but higher (5261 eV) for barium hydroxides due to the influence of the ‘A’ component. ‘B’ is present in aragonite-group minerals (witherite and alstonite) and may be a fingerprint of that structural state. ‘C’ and ‘D’ overlap and form a board hump at ∼ 5270 eV, but the relative proportions of ‘C’ and ‘D’ are variable between phases and are to some degree diagnostic. Refinement of Extended X-ray Absorption Fine Structure (EXAFS) allows estimates of first shell (Ba–O) bond distances in all materials, which are within 4% of average distances estimated from diffraction studies. Subsequent shells (Ba–S for barite; Ba–metal in witherite, alstonite and barytocalcite) can be resolved. The state of Ba:Ca order in alstonite and barytocalcite is successfully modelled and both are found to be fully ordered. The significant static disorder in Ba-bearing minerals is accommodated successfully by large Debye–Waller values in the refinements. Combinations of XANES and EXAFS allow all phases to be identified, with the exception that the two hydrated barium hydroxides cannot be distinguished from each other. The XANES of a celestite (SrSO4 containing ∼ 100 ppm Ba) is comparable to the barite spectra after only seven cycles (collected over < 5 h), showing that XANES can be resolved in samples with low Ba concentrations. However we were unable to analyse successfully an aragonitic Porites coral skeleton (containing ∼ 3–4 ppm Ba) using the current instrumentation due to the proximity in energy of Ca Kα secondary X-radiation to the Ba Lα energy and which overloaded the X-ray detector. The use of multilayer crystal detectors will be required to resolve the Ba Lα energy in calcium carbonate samples containing low Ba concentrations. Alternatively Ba EXAFS may be accessible through the Ba K edge.

Open Access

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Abstract: Some plant growth promoting bacteria (PGPB) are enigmatic in enhancing plant growth in the face of increased metal accumulation in plants. Since most PGPB colonize the plant root epidermis, we hypothesized that PGPB confer tolerance to metals through changes in speciation at the root epidermis. We employed a novel combination of fluorophore-based confocal laser scanning microscopic imaging and synchrotron based microscopic X-ray fluorescence mapping with X-ray absorption spectroscopy to characterize bacterial localization, zinc (Zn) distribution and speciation in the roots of Brassica juncea grown in Zn contaminated media (400 mg kg−1 Zn) with the endophytic Pseudomonas brassicacearum and rhizospheric Rhizobium leguminosarum. PGPB enhanced epidermal Zn sequestration relative to PGBP-free controls while the extent of endophytic accumulation depended on the colonization mode of each PGBP. Increased root accumulation of Zn and increased tolerance to Zn was associated predominantly with R. leguminosarum and was likely due to the coordination of Zn with cysteine-rich peptides in the root endodermis, suggesting enhanced synthesis of phytochelatins or glutathione. Our mechanistic model of enhanced Zn accumulation and detoxification in plants inoculated with R. leguminosarum has particular relevance to PGPB enhanced phytoremediation of soils contaminated through mining and oxidation of sulphur-bearing Zn minerals or engineered nanomaterials such as ZnS.