Journal of Analytical Atomic Spectrometry最新文献

Advancements in scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX) technologies have reached the point where rapid, fully quantitative, non-destructive and high-resolution acquisition of effectively all major element chemical information from polished sample material is possible. Here, we discuss optimisation parameters and demonstrate the data quality that can be achieved for SEM-EDX analysis of magmatic glass samples; glass represents a particular challenge due its lack of stoichiometry and potential for beam-induced element mobilisation. We test our approach through analysis of reference materials and demonstrate the advantages of SEM-EDX for several volcanic glasses that were previously investigated with electron probe micro-analysis (EPMA). SEM-EDX analysis is typically undertaken at a much lower beam current than EPMA, allowing for non-destructive analysis of geologic material that are sensitive to a higher beam current, such as sodium-rich glass. With careful instrument set-up, robust standardisation, and optimal experiment parameters, SEM-EDX analysis can achieve major and minor element data comparable with that collected via EPMA, with the exception of low abundance elements (those below 0.2 wt%). In addition, SEM-EDX analysis typically uses a smaller beam diameter and so permits analysis of smaller features than EPMA. Our results show that this technique can be potentially used as a quantitative tool on a wide range of geological materials with faster analysis, improved spatial resolution and cost advantages making it a complementary or alternative analytical method to EPMA.

We have developed a new method for measuring mass dependent Si isotope fractionation via critical mixture double-spiking. Samples need to be spiked before column chemistry to guarantee full equilibrium between the sample and double-spike (²⁹Si–³⁰Si spike). An iterative addition of the double-spike to the sample, usually 2–4 times, is needed to generate a solution very close to the critically spiked mixture. We use a double-pass cyclonic quartz spray chamber, as it gives the highest signal-to-noise ratio. In conjunction with 6 μg ml⁻¹ Si solution to yield intense Si isotope beams, this setup results in an ∼25 V (with 10¹¹ Ω resistor) signal on ²⁸Si⁺, while on-peak noise is less than 0.06 V. A typical sample analysis comprises 8 repeats (n = 8) of an individual sample measurement (for each repeat n = 1, 168 second analysis time) normalised to bracketing measurements of critically double-spiked NIST SRM 8546 (commonly known as NBS28). Each of these n = 8 analyses consumes about 13 μg of sample Si and yields a mean δ^30/28Si with a precision of approximately ±0.03‰ (2 s.e., 2 × standard error of the mean). Over a 16 month period, the reproducibility of the 11 mean δ^30/28Si values of such n = 8 analyses of the silicate reference material BHVO-2 is ±0.03‰ (2 s.d., 2 × standard deviation), which is 2 to 8 times better than the long-term reproducibility of traditional Si isotope measurement methods (∼±0.1‰, 2 s.d., δ^30/28Si). This agreement between the long-term and short-term variability illustrates that the data sample the same population over the long and short terms, i.e., there is no scatter on the timescale of 16 months additional to what we observe over twenty hours (the typical timescale in one analytical session). Thus, for any set of n repeats, including n >8, their 2 s.e. should prove a useful metric of the reproducibility of their mean. Three international geological reference materials and a Si isotope reference material, diatomite, were characterised via the critical mixture double-spiking technique. Our results, expressed as δ^30/28Si_NBS28, for BHVO-2 (−0.276 ± 0.011‰, 2 s.e., n = 94), BIR-1 (−0.321 ± 0.025‰, 2 s.e., n = 27), JP-1 (−0.273 ± 0.030‰, 2 s.e., n = 19) and diatomite (1.244 ± 0.025‰, 2 s.e., n = 20), are consistent with literature data, i.e., within the error range, but much more precise.

X-ray spectra are pivotal for understanding chemical bonding and atomic interactions in materials. Particularly, valence-to-core (VtC) electronic transitions and satellite peaks within X-ray spectra provide insights into valence states and chemical environments. This study focuses on the multi-vacancy satellite peaks, Si Kβ^III and Kβ^IV, and their application in analyzing silicate minerals in igneous rocks. A wavelength dispersive X-ray fluorescence (WD-XRF) spectrometer, commonly employed for chemical analysis of geological samples, was utilized in this study. The Si Kβ^III and Kβ^IV peaks were selected due to their VtC transitions and multi-vacancy origin, offering enhanced sensitivity to the chemical environment. We examined 41 certified reference materials (CRMs) of igneous rocks, demonstrating the capability of these satellite peaks to reveal detailed chemical and structural information. A strong correlation was found between the chemical composition of silicate minerals and the intensities along with chemical shifts of the Si Kβ^III and Kβ^IV peaks. We developed a regression model to predict mineral concentrations, validating the method with CRMs. The results suggest that the spectral region of the Si Kβ^III and Kβ^IV peaks serves as a distinctive fingerprint for identifying silicate minerals in igneous rocks.

The detection of impurities in diatomite is a critical issue during the silicon extraction process. Impurities can significantly impact the properties of silicon, compromising the performance of Si solar cells. In the present work, we applied a sensitivity-improved calibration-free LIBS measurement approach to assess the quality of diatomite. Based on the recording of two spectra with different delays between the laser pulse and the detector gate, the method enables the quantification of major, minor, and trace elements. The limits of detection for minor and trace elements were evaluated. Furthermore, we investigated the morphology and properties of the diatomite surface using Energy-Dispersive X-ray Spectroscopy and Scanning Electron Microscopy analysis. This research contributes to process optimization in the fabrication of electronic grade silicon from diatomite for photovoltaic technology and other applications.

The storage and management of nuclear waste materials require the detection of uranium, but traditional analytical methods are unsuitable for radioactive environments. The enhancement methods of uranium in glass matrices using fiber-optic laser-induced breakdown spectroscopy are still underdeveloped. Using an optical diagnostic system coupled with fast photography, shadowgraphy, and optical emission spectroscopy, the evolution of laser-induced plasma generated from a glass matrix under spatial confinement is studied. The plasma evolution image illustrates the temporal consistency between the compression of plasma width and the enhancement of luminescence intensity. Two enhancements were observed when the plate spacing was smaller than the plasma, which might be due to the high density of the core plasma or a synergistic effect of plasma expansion and shockwave confinement. Under spatial confinement, there is a 3–4-times enhancement in the intensity of uranium spectral lines and a 2–4 times enhancement in the signal-to-noise ratio. Several calibration curves are established under spatial confinement based on U II 409.01 nm, U II 367.01 nm and U I 358.48 nm. The lowest limit of detection (LOD) of uranium reaches 95 ppm, which supports the application of FO-LIBS in the detection of uranium-containing nuclear waste materials.

The rapid determination of per and polyfluoroalkyl (PFAS) persistent organic pollutants is of growing interest but remains instrumentally challenging. Traditional techniques require some preliminary knowledge of the target species and often time-consuming multistep procedures. Often, the concentration and compositional range of sample contamination is unknown. This is a limitation in investigating the level and fate of a new material's environmental footprint. The liquid sampling – atmospheric pressure glow discharge (LS-APGD) is a microplasma ionization source which provides combined atomic and molecular (CAM) information about analytes. To extend upon the demonstrated applications of the ionization source, the LS-APGD was coupled to an Orbitrap Fourier transform mass spectrometer (FT-MS) to characterize its capabilities towards the analysis of PFAS compounds, including perfluorooctanoic acid (PFOA) and perfluorooctyl sulfonic (PFOS) acid, extending to the perfluoro sulfonamides, acrylates, and telomer alcohols (FTOH). Across the board, these compounds pose incredible analytical challenges regarding the diverse matrices where they are found, their ubiquitous nature (including the laboratory), the lack of a universal ionization method, and the necessity for complex preconcentration/separation prior to MS analysis. The efforts here set the basic characteristics for such analyses, with the caveat that this laboratory is not outfitted for high-sensitivity PFAS analysis, setting up opportunities for more in-depth developments in the future. The mass spectral features for the respective compound types are very uniform, with those of PFOA, PFOS, sulfonamides, and acrylates dominated by their respective M–H (deprotonated) pseudomolecular ions. FTOH compounds were determined by identifying a common characteristic fragmentation pathway. The simplicity of the spectra and high mass resolution/accuracy suggest that determinations might be made without chemical separations. Linear response curves are realized for all species, with limits of detection of 20 pg mL⁻¹ (PFOA) and 310 pg mL⁻¹ (PFOS) obtained, without pre-concentration, for 60 μL infusions. In contrast to the established electrospray ionization (ESI-MS) methods, the CAM/Orbitrap coupling provides species selectivity across the entire breadth of the PFAS compounds and the potential for mixture discrimination without prior chromatographic separation or preconcentration.

A novel method for the speciation and quantification of polysulfide anions and molecular sulfur in lithium polysulfide solutions in organic solvents is reported. The technique is based on hyphenation of high-performance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICP-MS). A sector-field mass-spectrometer was utilized which made it possible to quantify various sulfur compounds without the need for single component standards and conduct the direct detection of the main isotope of sulfur regardless of interferents such as highly abundant ¹⁶O₂. Key aspects of separation and sample preparation were considered which allowed complete separation of derivatized polysulfide anions. Gradual adjustment of essential parameters and hardware is described. Variation of plasma settings allowed for obtaining chromatograms with desired analyte peak shapes. The optimized method was applied for the quantification of various lithium polysulfide mixtures in organic solvents showing the accessibility of the corresponding polysulfide distributions with this technique.

Rutile is an accessory mineral that is widely distributed in magmatic, metamorphic, and sedimentary rocks. Thus, rutile U–Pb geochronology and geochemistry (e.g., Zr-in-rutile thermometry) can provide important information on the geological evolution of a region. Accurate and precise in situ U–Pb dating and trace element content measurement require well-characterized reference materials to correct matrix-dependent elemental fractionation. We present a natural rutile reference material (the KNW rutile) for microbeam U–Pb age and trace element determination. The KNW rutile was collected from a pegmatite in Kragerø, Norway, which is ∼20 km east of the location where the R10 rutile was sampled. It is ∼21 mm × 10 mm × 8 mm in size, with a total mass of ∼30 g. The KNW rutile has a homogeneous U–Pb age, as shown by numerous LA-ICP-MS spot analyses (weighted mean ²⁰⁶Pb/²³⁸U age = 1089.5 ± 3.3 Ma; MSWD = 2.7; n = 229). KNW rutile contains very little common Pb with only 12 of 241 spot analyses showing an amount of common Pb (f₂₀₆: 0–20%). Seven ID-TIMS analyses produced a concordia age of 1088.2 ± 1.5 Ma (MSWD = 0.63) and a weighted mean ²⁰⁶Pb/²³⁸U age of 1088.2 ± 1.9 Ma (MSWD = 0.19), which is our recommended U–Pb age. The degree of homogeneous distributions of eleven trace elements was evaluated using LA-ICP-MS and EPMA. V, Cr, Nb, Sc, Zr, and Hf are sufficiently homogeneously distributed, whereas Ta, U, Pb, Fe, and W are heterogeneous. The determination of reference values for Zr and other trace elements as well as their uncertainties at the 95% confidence level followed International Organization for Standardization (ISO) guidelines and the certification protocol of the International Association of Geoanalysts (IAG) closely. The KNW rutile has a Zr content of 1183 ± 198 μg g⁻¹ (95% confidence level). The KNW rutile is a useful addition to the reference materials previously distributed for microbeam U–Pb age and trace element determination.

Laser-induced breakdown spectroscopy (LIBS) quantitative analysis is susceptible to matrix effects, especially in samples with significant differences in texture, such as soil and coal. Adding additional information such as the physicochemical properties of the sample and plasma images based on the original spectrum is an effective measure to reduce substrate effects. In this study, a new strategy to mitigate the impact of matrix effects and a high-accuracy quantification method for elements in soil by LIBS called PCA-GS-ELM are proposed. No additional equipment is required to obtain auxiliary information. Principal component analysis (PCA) is employed to extract spectral differences between different samples, and the differential spectrum is combined with the original spectrum to form the generalized spectra (GS), which is then input into the extreme learning machine (ELM) model. The model is trained to simultaneously focus on the element characteristic spectral lines and matrix differences between samples. In the experiment, a self-developed portable high-frequency LIBS is used. In the quantitative analysis of six major elements in 13 soil samples, the PCA-GS-ELM method has significantly improved accuracy. The RMSEP for Si, Al, Ca, Fe, Mg, and Ti is 0.946, 0.278, 0.394, 0.08, 0.169, and 0.034 wt%, respectively. The results demonstrate that the proposed generalized spectral method can mitigate matrix effects and enhance the performance of multivariate analysis methods.

In this work, the potential for direct major component analysis of lithium–nickel–manganese–cobalt oxide variants in solid samples by graphite furnace atomic absorption spectrometry (SS-GF AAS) was critically evaluated, always with the aim of developing a simple and rapid method that relies only on the use of aqueous standards for calibration. The accuracy of the developed method was evaluated against an established wet chemical acid digestion method using an inductively coupled plasma optical emission spectrometer (ICP-OES). The most challenging aspect was the selection and use of suitable standards, whereby the analytical performance criteria of liquid standards, single oxide solid standards and multi-element solid standards had to be determined. With the result that multi-element liquid standards can be used for calibration, very good agreement with the certified reference values and with the values obtained by ICP-OES was achieved in all cases. The precision of the method was better than 12% with an optimum sample mass of 0.2–0.4 mg. The results show that not only the major components in pure NMC compounds (e.g. starting materials) can be reliably analysed, but also the cathode coatings made from recycled battery materials. This demonstrates the range of applications of the methods and their suitability under industrial conditions, for example in the analysis of recyclates. The technology is almost predestined for use in industrial laboratories in order to quickly and accurately determine the stoichiometric composition of cathode coatings from aged lithium batteries and to ensure battery shredding by type.