Journal of Analytical Atomic Spectrometry最新文献

This study investigates the potential of femtosecond laser ablation coupled with multicollector inductively coupled plasma mass spectrometry (fs-LA-MC-ICP-MS) for copper isotopic analysis in gold matrices applied to cultural heritage. Elemental analyses, which have commonly been used so far, provide information on the circulation of metal stocks based on elemental signatures but fail to pinpoint the precise source of gold. In contrast, isotopic analyses can offer a more accurate means of identifying the source of the metal, yet their application to gold matrices remains a challenge. For the first time, we successfully determined copper isotope ratio in gold matrices and achieved repeatabilities of 0.12‰ to 0.26‰ (2SD) for δ⁶⁵Cu analyses carried out over up to 8 days, demonstrating the feasibility of copper isotopic analyses in gold coins at the micron-scale. This work was conducted using isotopically characterised in-house matrix-matched gold standard with copper concentrations varying from 4.5 wt% to 9.6 wt%. Our results open new avenues of research for provenance studies of precious museum artefacts and archaeological finds, with potential applications in authentication analyses on similar gold materials. The micro-sampling performed by femtosecond laser ablation minimises the damages on such ancient artifacts. However, the Cu concentrations had to be of at least 4 wt% with our analytical set up and a special care must be taken on the laser beam focusing in order to obtain accurate δ⁶⁵Cu measurements in gold matrices.

The effect of anode geometries on the analytical performance of the solution-cathode glow discharge (SCGD) source was investigated using tungsten rods with varying diameters and conical angles for atomic emission spectroscopy (AES). Under optimal operational parameters (electrolyte solution: HNO₃ at pH 1.0, discharge current: 65 mA, solution flow rate: 1.9 mL min⁻¹, and discharge distance: 2.0 mm), the highest emission intensity and stability for Na, Rb, K, Li, and Cs were obtained at the tungsten rod with a diameter of 2.4 mm, with relative standard deviations (RSD) of 1.14%, 0.93%, 1.01%, 1.25%, and 0.94%, respectively, while achieving the best detection limits (DLs). Additionally, when the anode tip had a conical angle of less than 30°, thermal melting resulted in discharge instability. A conical angle greater than 90° induced thermal spreading, leading to instability. Higher emission intensity stability and lower DLs were achieved with a conical angle of 60°. These results may provide new insights for enhancing the performance of SCGD systems.

A portable platform for the visual determination of F⁻ and Al³⁺ was developed by combining FeNPs@g-C₃N₄ nano-enzyme and a smartphone. The FeNPs@g-C₃N₄ nano-enzyme with excellent peroxidase activity was synthesized through the in situ growth of Fe nanoparticles (FeNPs) on graphite-phase carbon nitride nanosheets (g-C₃N₄), which could catalyze H₂O₂ to oxidize TMB to blue oxide (oxTMB). The peroxidase activity of the FeNPs@g-C₃N₄ nano-enzyme could be inhibited by F⁻, and then restored by Al³⁺ because of the coordination reaction between Fe³⁺/Al³⁺ and F⁻. Furthermore, the solution color could be dynamically manipulated by changing the concentrations of F⁻ and Al³⁺. Under optimal conditions, the developed method gave low detection limits of 2.43 nM for F⁻ and 7.66 μM for Al³⁺. The cooperation of nano-enzyme and smartphone has greatly shortened the detection time and reduced the cost of detection, providing a new strategy for the on-site and convenient detection of F⁻ and Al³⁺ in tea, and showed significant application potential in food safety evaluation.

Nanoparticle-Enhanced Laser-Induced Breakdown Spectroscopy (NELIBS) is a LIBS variant that, in its original implementation, is based on intensifying the emission intensity of the sample under investigation by depositing nanoparticles on its surface. In this work, we evaluated the feasibility of this approach for the analysis of historical samples by carrying out NELIBS of a bronze archaeological object. Our purpose was exploiting the emission enhancement to perform single-shot analysis of ancient metallic samples and to improve the LOD (Limit Of Detection) of minor and trace elements while also reducing the sample damage. To this end, we carried out LIBS and NELIBS analysis of one bronze helmet fragment (VII century BCE), and we adopted two different analytical approaches i.e., calibration lines drawn with a set of copper-based standard alloys, and Calibration-Free (CF). When depositing NPs on the surface of the archaeological sample, some critical issues arose, which have the potential to limit the applicability of NELIBS to metallic samples with surfaces altered by corrosion and burial deposits, such as those of ancient artifacts. We discussed these issues and proposed experimental and analytical approaches to mitigate their detrimental effects on the analysis. Our results showed that the LOD decreased for all the elements analyzed in the standard alloys and in the archaeological sample, though not in the same extent, and confirmed that, while requiring some special care for experimental optimization and data analysis, NELIBS can be a powerful approach in heritage science studies.

High-Energy Resolution Fluorescence Detection X-Ray Fluorescence (HERFD-XRF) imaging and HERFD X-ray Absorption Near Edge Structure (XANES) spectroscopy are used to quantify and characterize trace platinum (Pt) in gold solidi from the Late Roman and Byzantine Empires. Historically, the elemental analysis of coins has been pivotal in distinguishing authentic artifacts from forgeries, elucidating minting practices, and understanding economic shifts. Notably, a new gold source with high platinum content appeared in the fourth century CE, transforming the Roman economy. Traditional methods struggled to detect platinum due to the overwhelming gold matrix. This study demonstrates the effectiveness of HERFD techniques in resolving this challenge. Three gold solidi, minted between 654 and 659 CE, were analyzed alongside reference gold materials with known Pt concentrations. The HERFD-XRF imaging revealed spatial distributions of platinum, highlighting non-uniformities within the coins. Additionally, HERFD-XANES spectroscopy identified the oxidation states and chemical speciation of platinum. Results demonstrate that platinum in the solidi primarily exists as metallic Pt, with some surface oxidation. The findings align with previous measurements but reveal higher Pt concentrations and significant inhomogeneities. This research confirms the reliability of HERFD methods for quantifying trace elements and provides new insights into the raw material sources and minting techniques of ancient gold coins. The non-destructive nature of this approach allows for extensive analyses, offering valuable data for historical, economic, and archaeological studies. This innovative application of HERFD-XRF imaging and XANES in cultural heritage research underscores the potential for detailed material characterization and conservation, enhancing our understanding of ancient economies and trade patterns.

Determination of metal elements in columbite ores is of great importance in understanding the potential economic significance and the origin of deposits. LA-ICP-MS is recognized as a green and efficient method for the bulk analysis of trace elements in natural samples. However, a major issue is the lack of matrix-matched reference materials for columbite ores. In this study, we developed an advanced method to produce pressed ultrafine-powder pellets with appropriate concentrations by applying a wet-mill method. The optimized scheme achieves a typical grain size of d₉₀ = 1.74 μm, forming pressed powder pellets with great cohesion and homogeneity, suitable for LA-ICP-MS. The relative standard deviation (RSD) values obtained from repeated measurements are <10% for more than 50 elements, comparable to those of homogeneous reference glasses. A systematic investigation of glass reference materials, commercial iron ore pellets, and our synthetic columbite ore pellets revealed significant matrix effects in various materials when using nanosecond laser ablation. Although the use of a femtosecond laser ablation system can partially suppress the matrix effect that occurs during the laser ablation process, the matrix effect in the ICP caused by differences in chemical composition remains challenging to resolve. The use of a “wet” plasma mode enhanced the matrix effect. Our results highlight the importance of matrix-matched reference materials in quantitative analysis of columbite ores and other ore samples. Utilizing the matrix-matched calibration method, we successfully determined trace elements in pressed powder pellets of iron ore (MAKR-NP) and columbite ore (LSC), with discrepancies of less than 10% for most elements.

Matrix-assisted ionization (MAI) of inorganic analytes is a nascent research domain that holds promise for rapid, potentially facility-deployable analytical applications. We present results of MAI uranium isotopic analysis (²³⁵U/²³⁸U) obtained on the timescale of minutes utilizing simple sample preparation and an ambient ionization time-of-flight mass spectrometer (ToF MS). Experimental MAI-ToF MS characterization of uranium Certified Reference Materials (CRMs) was used to establish method calibration and validate quantitative ²³⁵U/²³⁸U determination spanning depleted, natural, and low-enriched uranium isotopic compositions. Secondary standard analyses with total uranium mass loadings of 5–500 ng per analysis yield accurate calibrated ²³⁵U/²³⁸U results and relative uncertainties of 4.7–17.2% (approx. ±95% confidence level), with weighted-mean uncertainties approaching 1.5%. This method permits accurate determination of uranium isotopic composition in a sample with uranium content as low as 200 pg for equal atom ²³⁵U:²³⁸U. Instrument detection limits constrain the minimum uranium mass required to identify the presence of highly enriched uranium (HEU ≥20% ²³⁵U) as only 500 pg using the method presented here. MAI-ToF MS quantitation of relatively extreme isotope ratios (²³⁵U/²³⁸U ≤ 0.01) is limited by detection of minor ²³⁵U (LoD 100 pg ²³⁵U/analysis ≈ 10 ng total U/analysis), and subsequent method optimization is anticipated to further reduce these limits. These findings underscore the potential of MAI-ToF MS for isotopic characterization of uranium and other inorganic species for both basic and applied science.

Methylmercury (MeHg⁺) is a highly toxic compound with significant neurotoxic effects, necessitating precise and reliable quantification methods for its assessment in biological tissues. In this study, we developed and optimized a methodology combining Microwave-Assisted Extraction (MAE), derivatization by phenylation, and preconcentration through Liquid Phase Microextraction (LPME), coupled with Gas Chromatography-Pyrolysis-Atomic Fluorescence Spectrometry (GC-PYRO-AFS) for the selective quantification of MeHg⁺ in mouse brain tissue. The optimized method demonstrated high sensitivity and reproducibility, enabling the accurate detection of MeHg⁺ at trace levels without significant matrix effects. This methodological advancement is particularly important in the field of toxicology, as it addresses the limitations of traditional techniques by reducing analysis time and cost while improving accuracy. The ability to precisely quantify MeHg⁺ concentrations in biological tissues facilitates the study of toxicokinetic behaviors, the proposal of distribution mechanisms, and the evaluation of toxicological impacts, ultimately contributing to the development of biomarkers for human health risk assessment.

Since the establishment of the single-element Ti-in-zircon thermometer in 2005, it has been extensively applied to estimate the crystallization temperatures of zircon due to its simplicity and convenience. Then, the thermometer was modified in the subsequent work, considering the effect of pressure as well as the activities of SiO₂ and TiO₂, even though whether or not the other competitive trace elements can also influence the predicted temperatures remains ambiguous. Here, an advanced high-dimensional temperature prediction model has been developed, which is based on the XGBoost algorithm and utilizes comprehensive trace element concentrations within zircon, achieved through training and comparing various machine learning algorithms. This model integrates a multitude of factors, not only the activities of SiO₂ and TiO₂, but also the intricate composition of trace elements and their interactivities. Four evaluation metrics, namely R², RMSE, MAE, and EV, were utilized to assess the algorithms' capabilities. The results show that it is imperative to consider all the trace elements within zircon as an integrated system, rather than only a few specific elements for accurate temperature prediction. Moreover, an in-depth analysis of the high-dimensional model was conducted by introducing SHAP, and it exhibits either positive or negative relationships between the trace elements and temperature. Finally, this model was applied to zircons crystallized in various temperature ranges from all over the world, which unveil features characterized by “both unity and diversity”. In summary, the XGBoost model is strongly recommended for temperature prediction in comparable regions and temperature ranges.

The oxidation state of iron (e.g., Fe³⁺/ΣFe) in minerals is a direct proxy for the oxygen fugacity of magma and fluid, which plays a key role in the formation of various types of ore deposits. Although many techniques have been developed to determine the Fe³⁺/ΣFe ratio in minerals, the electron microprobe flank method is particularly notable for its easy accessibility and high efficiency. However, the application of this method is limited by a shortage of suitable calibration standards. In this study, we collected a series of natural, euhedral garnet grains and gem-quality garnet fragments, which were carefully crushed and separated under a binocular microscope. Following a detailed examination of their major element compositions and Mössbauer spectroscopy measurements for their Fe³⁺/ΣFe ratios, we report ten new garnet samples (three belonging to the andradite–grossular series and seven to the almandine–pyrope–grossular series) that can be used as reference materials to calibrate the Fe³⁺/ΣFe ratio of garnet using the flank method. The andradite–grossular samples are highly enriched in Fe³⁺, exhibiting Fe³⁺/ΣFe ratios ranging from 0.89 ± 0.03 to 1.00 ± 0.03, while the almandine–pyrope–grossular samples contain minimal Fe³⁺ with Fe³⁺/ΣFe ratios ranging from 0.01 ± 0.02 to 0.03 ± 0.01. One andradite sample (And1902) and one almandine sample (Ald1906) were identified as ideal for determining the flank positions for Fe L_α and Fe L_β. These two end-members, along with the other eight samples, can be employed to quantify the relationship between Fe L_β/L_α at flank positions and the Fe²⁺ or ΣFe content. The results indicate that the Fe²⁺ contents and Fe³⁺/ΣFe ratios of the ten garnet samples align with those obtained through Mössbauer spectroscopy, with an uncertainty of ±1 wt% for Fe²⁺ and ±0.05 for Fe³⁺/ΣFe, respectively. Consequently, these well-characterized natural garnet samples can serve as reliable reference materials when synthetic garnet standards are unavailable.