Spectrochimica Acta Part B: Atomic Spectroscopy最新文献

Separation and preconcentration procedures are often necessary to eliminate interferents, enhance sensitivity, and improve detection limits. Conventional solid-phase extraction (batch) finds extensive applications in the determination of various analytes, particularly in low concentrations and complex matrices such as environmental, food, and biological samples. However, drawbacks include high reagent consumption, time-consuming sample processing and low analytical throughput. To address these issues and promote Green Analytical Chemistry (GAC), novel methods have emerged, with solid-phase and liquid-phase microextraction being notable examples. Thin Film Microextraction (TFME) represents an innovative approach involving a solid support coated with a thin layer of adsorbent material, attached to a rod and immersed in the sample solution. Extracted analytes can be quantified either after desorption (elution) or directly on the thin film. This article aims to explore TFME's potential when combined with Laser-Induced Breakdown Spectroscopy (LIBS) for Cd, Cr and Ni determination using lignin as adsorbent material deposited on a solid substrate by dip coating. Under optimized conditions, limits of detection obtained were 1.76 μg kg⁻¹ (Cd), 5.72 μg kg⁻¹ (Cr), and 3.27 μg kg⁻¹ (Ni). The accuracy of the proposed method was evaluated through the analysis of a certified reference material (ERM® CA713), drinking and tap water.

CSigma laser-induced breakdown spectroscopy (Cσ-LIBS), as the other methods for quantitative elemental analysis by LIBS based on plasma characterization, is negatively affected by the inhomogeneity of laser-induced plasmas. In the present work, we propose a new procedure for Cσ-LIBS which addresses the plasma inhomogeneity problem. The key features of the method are: (1) the extension of the concept of apparent temperature to other plasma parameters (apparent plasma) and its use in both the ionization and excitation equilibria and (2) the addition to the theoretical Cσ curve of a linear contribution arising from the plasma regions of low optical depth. In ionization equilibrium, the inhomogeneity requires separated Cσ graphs and different apparent ionization temperatures for neutral atom and ion emissions. In excitation equilibrium, we account for the inhomogeneity by obtaining a different apparent temperature for each multiplet included in the Cσ graph. In this way, the procedure only requires the fitting of a limited number of parameters to describe the inhomogeneous plasma, as the multiplet temperatures $T_i$ are determined by a straightforward iteration procedure of fast convergence. The improved treatment of plasma inhomogeneity allows to include intense resonance lines in Cσ graphs, which were previously avoided. The development of the method has demanded accurate experimental Cσ graphs, obtained with seven certified aluminum alloys. The laser-induced plasma is generated in air at atmospheric pressure, the most common and versatile ambient gas condition for LIBS, which is known to produce a strongly inhomogeneous plasma. To validate the analytical application of the method, the samples are divided into three characterization samples and four analytical samples. The average deviation of the determined concentrations from the certified values has been 8.5% for elements with concentrations greater than 0.05 wt%.

NdFeB material has excellent comprehensive magnetic properties, which plays a crucial role in the field of rare earth magnetic materials, and is one of the important basic materials to support modern high-tech industries. In the production of NdFeB alloys, the control of rare earth elements (REEs) is directly related to the quality and resource utilization efficiency of NdFeB materials. Therefore, the prediction of REEs content in NdFeB alloys is of great research significance and application value for the quality control of products, the enhancement of production efficiency and reduction of energy consumption by the rare earth material industry. In this study, a combination of laser-induced breakdown spectroscopy (LIBS) and random forest (RF) was used to investigate the quantitative analysis of four REEs (Nd, Pr, Tb and Dy) in NdFeB alloys. Firstly, the original LIBS spectra were screened by principal component analysis-mahalanobis distance (PCA-MD). Then, the effects of different data processing methods on the screened LIBS spectra were explored, and next, the feature variables were extracted from the preprocessed spectral data by the variable importance measurement (VIM). In order to further verify the prediction performance of the model, the prediction results of the RF models based on the different methods were compared. Finally, a PCA-VIM-RF calibration model was established on the basis of the optimized spectra, selected feature variables and parameters. Leave-one-out cross validation (LOOCV) was used to optimize the parameters of PCA-MD method, spectral preprocessing method and variable importance thresholds during the construction of the calibration model. The results show that the PCA-VIM-RF model has better prediction performance than the RF calibration model based on the raw spectra. For the PCA-VIM-RF calibration method of Nd, Pr, Tb and Dy elements, the values of R²_CV are 0.9991, 0.9998, 0.9986, and 0.9984, respectively, the values of RMSE_CV are 0.06296%, 0.02788%, 0.04647% and 0.05252%, respectively. The values of R²_P are 0.9508, 0.9975, 0.9691 and 0.9457, respectively, and the values of RMSE_P are 0.6082%, 0.09205%, 0.5776% and 0.2631%, respectively.The above results indicate that LIBS combined with PCA-VIM-RF algorithm is a promising method for rapid quantitative analysis of REEs in NdFeB alloys without complicated sample preparation, which can provide some new ideas or strategies for the future research, development and quality control of rare earth materials.

The Nuclear Energy Agency (NEA) launched the Nuclear Education, Skills and Technology (NEST) Framework to pursue careers in the nuclear field, by exposing researcher working on these topics to international challenging project of real-world issue and by transferring the knowledge and expertise accumulated in the current generation to them through hands-on training.

In this framework the 2022 edition of the NEST project offered a training educational period at the Collaborative Laboratories for Advanced Decommissioning (CLADS) located at Tomioka, Futaba District, in the Fukushima prefecture (Japan).

Among the research sectors active at CLADS there is the application and development of the LIBS technique as diagnostics of analytical chemistry aiming at characterizing the debris inside the Tokyo Electric Power Company (TEPCO)’s FDNPS reactor cores after the tsunami of March 2011, which destroyed three of the six reactors of the plant. These debris need to be chemically characterized with techniques suitable to be implemented in compact, remote and radiation resistant devices, due to the residual radioactivity of the cores. The present study shows the results in realizing chemical bi-dimensional maps of samples in the form of compressed tablets of mixed oxides, with a complex distribution and concentration of chemicals simulating these debris. The results allowed to create detailed maps of the samples, with spatial resolution down to 0.5 mm and an excellent correspondence between the real spatial distribution of the materials and that reconstructed by LIBS.

Moreover, it was found a good correspondence between the nominal concentration of the chemicals and the concentration estimated by using LIBS.

This study shows the potentialities of LIBS in the realization of chemical maps on samples of interest for FDNPS, providing multi-elemental images of the samples under analysis.

Transport efficiency has become a critical parameter in single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) since it is involved in the calibrations to determine different measurands (element mass per particle, particle size and particle number concentration). Specific methods for its determination based on the use of particle standards have been developed and widely applied (particle frequency and particle size methods). A refined indirect method not relying on particle standards is also available (dynamic mass flow method). A number of discrepancies on the accuracy of these methods and their adequacy have become evident, making a revision of the topic pertinent. In fact, the application of the particle frequency and particle size methods determine the transport efficiencies corresponding to the particles or the dissolved element respectively, whereas the solvent transport efficiency is actually measured by the dynamic mass flow method. The use of each of these methods requires assuming different conditions that must be considered. These conditions, together with the sources of bias associated to each method are critically discussed to provide a holistic and harmonized view of transport efficiency in the context of SP-ICP-MS metrology.

As a representative soft ionization technique, electrospray ionization (ESI) is commonly applied for the analysis of organic and biological compounds and is less used in inorganic applications. This study introduces the performance of ESI high-resolution mass spectrometry (HRMS) in the detection of elements. The HRMS instrument was equipped with a sub-atmospheric pressure (SAP) ESI source to reduce sample consumption and simplify the sampling operations. In addition, in-source collision-induced dissociation (IS-CID) was introduced into the analysis to generate simple metallic ion species such as atomic ions and charged oxides and reduce organic peak interferences. Various solutions containing metal salts and organometallic compounds were analyzed, demonstrating a picogram-level absolute detection limit and accurate multi-element identification capability of the instrument. Furthermore, SAP-ESI-HRMS exhibits diverse analytical performances, enabling both elemental and organic analyses by simply regulating the IS-CID energy in the measurement.

This paper provides critical and constructive comments on the paper “Comparison of direct and indirect measures of transport efficiency in single particle inductively coupled plasma mass spectrometry” by K. E. Murphy, A. R. Montoro Bustos, L. L. Yu, M. E. Johnson, M. R. Winchester, which has been recently published in Spectrochimica Acta Part B. It details the author's reservations about the discussions and message of this paper. It calls the reader's attention to the paper conclusions and highlights which are not supported by the paper content/findings but they only mislead the reader with regards to the features and benefits of the dynamic mass flow (DMF) method reported for the first time by Cuello et al., Journal of Analytical Atomic Spectrometry, 2020, DOI: https://doi.org/10.1039/c9ja00415g and used by other groups and in interlaboratory comparisons at the metrological level for transport efficiency determination in spICP-MS measurements of particle number concentration.

The paper by Murphy et al. misses the key fact that DMF is not intended for use with any set up or condition but, if used under specified optimal operating set up and conditions (e.g. use of an ICP-MS system in equilibrium, a cooled spray chamber as reported by Cuello et al.) the method is invaluable for applications where use of the TEF and TES methods to determine transport efficiency is constrained by their reliance on reference materials which are limited or unavailable. The main use of DMF is the assignment of a SI traceable number concentration value to new, commercial nanomaterials and use those as quality control materials in spICP-MS experiments. This has not been highlighted explicitly in the paper under discussion. Instead, the findings rely heavily on data acquired by the DMF method using nineteen different conditions of which only one complies with the published recommendations and, unsurprisingly, for which the authors found the DMF to work. Indeed, some of the chosen operating conditions are unjustifiable given any knowledge of common ICP-MS usage. Yet this is used to justify condemning the DMF method and ignores the fact that close control of operating conditions is essential for many methods, particularly when striving for small uncertainty.

Self-absorption effect is always encountered in laser-induced breakdown spectroscopy (LIBS) and immediately distorts the calibration curves especially for the elemental determination of complex materials. With the aim to provide an expeditious approach for LIBS measurements susceptible to self-absorption effect, an exploratory study for sample preparation by powder mixing is implemented, and the self-absorption of laser-induced plasma beryllium emissions is investigated as a function of the dilution factor. For comparison, boric acid and wax powder are separately used as typical binding agent to mix with beryl powder to produce two sets of pressed pellets with sequential gradient of beryllium content variation. For the resonant lines most prone to self-absorption of Be II emission doublet at 313.042 nm and 313.107 nm, the beryllium spectral line shapes can be directly regulated and improved in the case of both sets of pellets as the dilution factor increases. In addition, the self-absorption effect for the strongly emitting beryllium spectral lines is further assessed by calculating the self-absorption coefficients based on the radiation transport equation. With regard to the both types of binder as diluent, when the dilution factor for beryl increases to 10 with a weight percent of 0.386% for beryllium in the pellet, the SA values may exponentially increase in general to around 0.8 and eventually asymptotically approaches to 1 without exception. Thus the self-absorption effect of laser-induced beryl plasma emissions can be readily overcome with sample preparation by powder mixing. By contrast with laser pulse irradiance in the present work, the dilution factor for powder mixing plays a dominant role in eliminating self-absorption effect. This research proposes a potentially effective approach to reduce self-absorption in laser-induced plasma emissions.