Journal of Analytical Atomic Spectrometry最新文献

Sulfur isotope microanalysis of calcite using secondary ion mass spectrometry (SIMS) enables high spatial resolution investigations of microstructures and biological influences – areas where conventional bulk analytical methods fall short. This technique relies heavily on matrix-matched reference materials. However, the development of SIMS applications in calcite is currently limited by the scarcity of such standards; only one calcite standard is available, and it lacks systematic assessment of isotopic homogeneity. In this study, a biogenic calcite sample (Jas-outer-Mariana) underwent 295 SIMS sulfur isotope analyses and was found to exhibit homogeneous sulfur isotopic compositions, with an external reproducibility of <0.41‰ (1σ), making it a promising SIMS reference material. Matrix effects were evaluated using various carbonate samples, including abiotic aragonite (Vs001/1-A), low-organic-matter biogenic calcites (G-Mariana and B-Indian), and a high-organic-matter biogenic calcite (C-Mariana). The results reveal substantial matrix effects on the secondary ion yields of sulfur and its isotopes, particularly between low- and high-organic-matter calcites, likely due to the presence of organic matter and organic sulfur. This study highlights both the potential and the limitations of in situ sulfur isotope analysis in calcite by SIMS and emphasizes the need for caution when interpreting data from high-organic-matter samples.

In this paper, we discuss strategies for analysing medium- and high-entropy ceramics (REE₃NbO₇) that contain 4 and 5 different rare-earth elements. In the coming years, it may be necessary to shift from laboratory-based analysis of ceramic powders to on-site examination of thermal barrier coatings, particularly those employed in aircraft engines. To address this, we employed a portable X-ray fluorescence spectrometer capable of in-field non-destructive simultaneous quantification of Gd, Er, Tm, Yb and Y. The major problem with portable systems is the overlap of Gd, Er, Tm, and Yb lines. Therefore, we conducted a complete comparative study of the strategies that allow for the acquisition of analytical signals in the energy-dispersive spectra. In order to critically evaluate the need for deconvolution, a technique often suggested in the literature, we used wavelength-dispersive X-ray fluorescence. This XRF variant was used to obtain spectra with higher resolution, and thus different levels of line overlap. In this work, we highlighted peculiarities of the deconvolution process in higher- and lower-resolution X-ray fluorescence spectra. The study revealed that the portable spectrometer is capable of accurately quantifying the concentrations of Gd, Er, Tm, Yb, and Y in both medium- and high-entropy ceramics. A comparative analysis showed that quantitative analysis of medium- and high-entropy ceramics does not require deconvolution of energy-dispersive spectra. It is shown that the samples synthesised using the reverse precipitation method allow one to obtain reliable calibration curves and avoid matrix effects using a portable X-ray fluorescence spectrometer, despite the fact that the concentrations of the major components vary 3 times. However, it was found that experimental conditions in a vacuumed wavelength-dispersive X-ray fluorescence spectrometer reduced trueness by approx. 9%. Nevertheless, this system proved to be a suitable substitute for ICP-OES in laboratory practices. The portable version, on the other hand, holds promise for in-field use.

In situ analysis of the chemical composition and a certain physical property of steel has a wide application prospect in many industrial fields, especially those involving the material's manufacturing and service. In this work, a novel approach based on laser-induced breakdown spectroscopy (LIBS) combined with a multi-task convolutional neural network (MT-CNN) is proposed for the simultaneous analysis of multiple chemical elements and the surface flatness of a steel material. To verify its superior performance, the MT-CNN model was compared with single-task CNN (ST-CNN) models. The comparative results indicate that the MT-CNN model is more effective in improving generalization performance and model robustness, as well as in reducing the risk of overfitting, which is attributed to the inherent information-sharing capability of the MT-CNN architecture. To uncover the black-box nature of the MT-CNN model, sensitivity analysis of wavelength variables was conducted to map the interpretability of the variables in predicting each task by the MT-CNN model. It was found that the importance of the variables can be explained by considering the formation and emission mechanisms of plasma generated by laser ablation of the steel surface and the correlations among the certified values of target quality indicators. The building framework of the proposed approach could be extended to resolve the issues associated with the in situ and simultaneous analysis of multiple quality indicators, including the chemical and physical properties of a target material.

This reply to the comment by Rose et al. demonstrates the validity of the results reported and conclusions drawn in DOI: 10.1039/d3ja00150d.

The polarization characteristics of element emission lines, influenced by local magnetic fields and atomic transition mechanisms in plasma, offer a promising approach to enhance the accuracy of laser-induced breakdown spectroscopy (LIBS) in complex matrices. To address the interference of soil matrix components in chromium detection and improve the stability of quantitative analysis, a polarization-resolved correction model has been derived based on Fresnel equations and Malus's law. This model establishes the relationship between the polarization state of plasma emissions and the complex refractive index at Brewster angle incidence, and insights have been provided on how laser polarization and angle influence plasma excitation efficiency and emission properties. 150 sets of LIBS and polarization-resolved LIBS (PRLIBS) data were collected by using soil samples spiked with five reference concentrations of Cr. Robust correlations between spectral line intensities and reference concentrations were established through linear fitting analysis, and the stability of spectral recognition was demonstrated. The results indicate that the polarization-corrected model significantly improves the linearity between the emission line intensities and the reference concentrations. Compared to conventional LIBS, the stability of the three characteristic emission peaks of Cr is markedly enhanced. By optimizing spectral line intensities through polarization orientation adjustment, the model effectively suppresses matrix-induced interference signals. This method demonstrates superior feasibility and reliability for in situ soil analysis, providing a powerful tool for accurate detection of heavy metals in environmental monitoring.

Due to the high dimensionality and non-linearity of the near infrared (NIR) spectral data, measuring outliers becomes difficult. During the near-infrared spectrum collection process, outliers usually appear due to factors such as uneven distribution of samples, environmental changes, measurement instrument deviations, improper operation, etc. These outliers will bias the direction predicted by the model, making the model prediction results unreliable. Therefore, it is necessary to eliminate the outliers in the process of near-infrared modeling to improve the accuracy of the model. This paper proposes an outlier detection algorithm based on high-dimensional subspaces. This algorithm first introduces a new method for determining local subspaces, which combines local sparsity with adaptive neighborhood selection to determine the local subspace. At the same time, we use the concept of jump degree to adaptively determine the anomaly threshold, thereby achieving the recognition of outliers. In order to investigate the effectiveness of the algorithm, a comparison was made with commonly used PCA-Mahalanobis distance, spectral residual (SR), and leverage method in terms of projection performance, to test the accuracy of the algorithm in distinguishing outliers. In addition, to verify the accuracy in processing high-dimensional data, we compared LoOP and SOD with our method. The experimental results showed that the subspace-based outlier detection method effectively improved the performance of outlier identification and calibration for NIR analysis.

We present the design of a spectral imaging inspection instrument based on a Digital Micromirror Device (DMD). The instrument utilizes an enhanced optical path that is compatible with the near-ultraviolet spectrum. The optical path design leverages the flexibility and high reliability of DMDs to enable precise control over spatial light modulation and spectral wavelength selection. Additionally, we evaluated the instrument's spectral range and spatial resolution using a mercury lamp and a resolution plate. The results indicate that the instrument operates within the 250–500 nm range, with a spatial resolution of up to 35 μm. Finally, we use the plasma generated by the Laser-Induced Breakdown Spectroscopy (LIBS) instrument as the observed sample. Instrumental observations reveal subtle spatio-temporal variations in the plasma across different spectral lines.

Cadmium (Cd), rhenium (Re) and thallium (Tl) are dispersed metals that serve as geochemical tracers for various geological and environmental processes. Both Cd and Tl exhibit high toxicity and slow metabolic clearance rates, posing risks to plants, animals, and humans. Determining their concentrations in natural samples is challenging due to their low abundance, especially in water samples where concentrations are typically in the range of ng L⁻¹ to μg L⁻¹. In this study, we developed a simple, efficient and robust method for the simultaneous separation and quantification of Cd, Re and Tl from a single sample aliquot using an anion exchange resin. Concentrations were subsequently measured by isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP-MS). The validity of this method was demonstrated through repeated analysis of reference materials BHVO-2, BIR-1a and GBW07105 (GSR-3). The results are consistent with previously published values within errors, including precision and accuracy. Additionally, the standard deviations of our concentration measurements are less than 1.49% for Cd, 3.83% for Re, and 1.63% for Tl in in-house water samples. The optimized approach was applied to river samples collected from the Pearl River tributaries. These investigations demonstrate that our sample purification and ID-ICP-MS measurement methods are effective for the quantitative determination of Cd, Re, and Tl concentrations in both rock and river samples. Our study enhances understanding of the aquatic geochemistry of Cd, Re, and Tl, thereby enhancing our ability to predict trace-element dynamics in hydrosystems.

Iron (Fe) isotopes serve as a powerful tracer for studying planetary evolution, magmatic processes, redox conditions, biological activities, and other key geological processes. However, the application of stable Fe isotopes in depleted-Fe samples has been significantly constrained by pervasive argon-related isobaric interferences inherent to conventional multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). This study purified rock samples with varying Fe concentrations and precisely measured Fe isotope ratios using the collision cell pathway in the low-resolution mode of the Nu Sapphire instrument. We systematically evaluated the effects of total Fe concentration in solution, Fe signal intensity mismatch between samples and standards, and HNO₃ molarity differences on measurement precision and accuracy. For precise Fe isotope ratio measurements using sapphire, strict analytical conditions must be met: (1) matched nitric acid concentrations between samples and bracketing standards (1% deviation induces 0.2‰ Fe isotope offset); (2) consistent Fe signal intensities (5% concentration mismatch introduces 0.05‰ bias); and (3) suppression of matrix interferences to minimize isotopic fractionation. The results demonstrate that the Nu Sapphire can achieve precise measurements with as little as 1 μg of Fe, representing a tenfold improvement relative to conventional instruments. The Fe isotopic data obtained for 13 geological references show good agreement with previous studies. Therefore, the exceptional sensitivity of Nu Sapphire facilitates high-precision Fe isotope ratio measurements for iron-depleted samples, offering broad application potential.

The application of monodisperse microdroplets for non-matrix-matched quantification in LA-ICP-TOFMS was investigated for inorganic and organic matrices. Suppression behavior in droplet signals caused by addition of typical major elements of geological samples (Al, Si, Ca, Ti, and Fe) in the μg g⁻¹ range was studied using microdroplets introduced via a falling tube and compared to solution nebulization. Signal suppression patterns observed for microdroplets could be attributed to neither mass load effects nor in-plasma oxide formation, nor reproduced via solution nebulization, suggesting a fundamentally different behavior of microdroplets in the plasma. Radial diffusion profiles were acquired to assess in-plasma behavior of droplets and laser-induced aerosol from NIST SRM 610 (glass). Diffusion profiles overlapped and showed similar full width at half maxima (FWHM) for microdroplets and the laser-induced aerosol, with minor spatial shifts in intensity maxima, likely due to not complete on-axis droplet introduction into the plasma. Quantification based on microdroplet calibration yielded relative deviations from reference values below ±20% across certified reference materials and an in-house prepared gelatine standard. Quantification of gelatine samples using NIST SRM 610 (glass) as an external standard resulted in larger deviations compared to droplet-based calibration, which yielded values in agreement with digestion data. These results demonstrate the suitability of monodisperse microdroplets for non-matrix-matched calibration in LA-ICP-TOFMS, particularly for elements non-certified or uncommonly reported in reference materials used in LA-ICP-MS.