Abstract:Lunar glass beads, formed through impact and volcanic processes, are used in SIMS U-Pb dating to provide valuable insights into the Moon’s volcanic activity and impact history. However, lunar glass beads exhibit a wide range of chemical compositions deviating from the commonly used glass reference materials. The lack of glass reference materials with high FeO content presents a challenge for correcting matrix effects in SIMS analyses of impact glasses with variable FeO contents. This study prepared and preliminarily characterized a new synthetic glass reference material (LMG-4) with compositions analogous to those of Chang’e-5 soils and mare basalts, plotting in the center of the published compositional range of Chang’e-5 impact glass beads. This glass exhibits significantly higher FeO and lower SiO2 contents than other available reference glasses, fulfilling the requirements for high-FeO glass reference materials. U-Pb-Si-O isotope ratios and Fe2+/ΣFe ratio were determined using bulk ID-TIMS, MC-ICP-MS, IRMS, and potassium dichromate volumetric method. The homogeneity of LMG-4 is confirmed through EPMA and SIMS spot analyses. This new synthetic glass reference material offers a potential solution for correcting matrix effects in U-Pb-Si-O isotope analyses of high-FeO glass using in situ microanalytical techniques.

Abstract:Lunar glass beads, including volcanic and impact origins, have become key targets for in-situ U-Pb dating using secondary ion mass spectroscopy (SIMS) to trace the thermal evolution and impact history of the Moon. However, the accuracy of SIMS U–Pb dating results is questionable without careful evaluation of matrix effect because of the largely variable major element contents of lunar glass beads which are also significantly different from the commonly used glass standards. In this study, we used seven glass standards with large variation of compositions, including three MPI-DING glasses, two USGS glasses, ARM-3 glass, and LMG-4 glass with composition simulating the Chang’e-5 lunar soils, to investigate the U-Pb fractionation behavior in SIMS analyses. Our results revealed more than a threefold variation in Pb+ ion yields, which positively correlated with the total FeO content (FeO(t)), and an eightfold variation in U+ ion yields, which negatively correlated with FeO(t). The relative sensitive factor (RSF) of (206Pb+/238U+)/(206Pb/238U) shows a variation of over 28-fold. Therefore, the traditional U/Pb calibration method based on only a single standard is insufficient to correct such a significant matrix effect. We propose a calibration protocol based on a linear relationship between ln((206Pb+/238U+)/(206Pb/238U)) and ln(UO2+/U+), or alternatively, ln(206Pb+/238U+/206Pb/238U) vs. ln(UO+/U+), and ln(206Pb+/UO+/206Pb/238U) vs. ln(UO2+/UO+). This method requires at least two glass standards with a large range of FeO(t) to effectively correct for matrix effects. Additionally, we recommend revised 206Pb/238U values for those glass standards that lack values determined by isotope dilution thermal ionization mass spectrometry (ID-TIMS), based on the observed fractionation rule in this study.

Abstract:Accurate determination of platinum group elements (PGEs) in active pharmaceutical ingredients (APIs) is critical due to stringent regulatory requirements and the potential toxicological effects of these elements. In this study, a microwave-assisted wet digestion (MAWD) method was developed to allow interference-free determination of PGEs, including Os, in APIs by inductively coupled plasma mass spectrometry (ICP-MS). Five widely used API samples were selected and a study of interferences was performed. The evaluated conditions included the composition of the digestion solution, and sample mass. The calibration and washing solution mediums were also evaluated: 5% HCl solution or a stabilizing solution (composed of acetic acid, thiourea and ascorbic acid). Furthermore, carbon interference (up to 2000 mg L-1 of C), which is critical for PGE determination by ICP-MS, was evaluated, and it was observed that C concentrations higher than 800 mg L-1 caused interferences for PGE determination, with the exception of Os. The method was validated according to the United States Pharmacopeia (USP). The optimized conditions for the proposed MAWD method were 500 mg of sample and a mixture of HNO3+HCl (1+1, 6 mL) as digestion solution. The 5% HCl solution was suitable for the determination of all PGEs, except for Os. In the case of Os, the stabilizing solution, added to samples, blanks, standards, and as washing solution, was necessary for its quantitative determination. The proposed procedure allowed quantitative PGE recoveries, including Os, using an efficient and relatively simple sample preparation method based on MAWD. Furthermore, the limits of quantification were suitable for PGE determination according to USP requirements.

Abstract:Lunar regoliths typically exhibit complicated mineralogy, texture, composition, and fine grain size, making them difficult to characterize using traditional mineralogical analytical methods. SEM-based automated mineralogy allows for quantitative and non-completely destructive assessment of bulk composition, mineralogical characteristics, and igneous rock types of lunar soils. Here, we use the TESCAN Integrated Mineral Analyzer (TIMA) to characterize a total of 79604 particles of Chang’e-5 returned lunar soil with a wide particle size range (>240 μm to <2 μm). The results showed that lunar soil mainly consists of pyroxene (36 wt. %), plagioclase (22 wt.%), glass (19 wt.%), olivine (9 wt.%), ilmenite (5 wt.%), SiO2 polymorphs (0.5 wt.%), apatite (0.2 wt.%) and troilite (0.2 wt.%), agreeing with those of the previous XRD and Raman analyses. The analytically calculated bulk compositions of the SiO2 (40.8 wt. %), MgO (6.8 wt.%), Al2O3 (10.8 wt.%), CaO (12.1 wt.%), and FeO (22.7 wt.%) were also consistent with those of the previous result obtained by wet chemical methods. The mineral association showed that basaltic pyroxene-plagioclase-olivine-ilmenite assemblages were the most common lithic clasts within lunar soil. These results indicate that Chang’e-5 lunar soil predominantly consists of local mare basalt. This study demonstrates the role of automated mineralogy technology in providing rapid, quantitative, and reliable mineralogical and compositional data, which are fundamental for investigating the bulk mineralogical and chemical characteristics of rare returned extraterrestrial materials.

Abstract:In forensic science, trace evidence establishes links between victims, suspects, and crime scenes. Head hair commonly serves as a reliable biomarker because it contains a permanent record of elements from an individual's body. By substituting CF4 reaction gas for polytetrafluoroethylene powder, this work modifies and re-optimizes a previous method for determining the sex of humans by directly analyzing hair samples via electrothermal vaporization with detection by inductively coupled plasma optical emission spectrometry. Hair samples were washed in portions of doubly deionized water, dried, and ground into a fine powder before analysis. Data processing included the use of an Ar emission line to compensate for sample loading effects on the plasma via point-by-point internal standardization. The peak areas were then integrated before multivariate analysis by principal component analysis (PCA) and linear discriminant analysis (LDA). Using the same predictor elements as the original method (Mg, S, Sr, and Zn), LDA and PCA remained effective at accurately predicting the sex of female and male samples despite using a different chemical modifier and instrumental operating conditions, indicating method robustness. This work thus offers an alternative method that uses a more affordable and accessible carrier agent at no cost to the original method's reliability.

Abstract:Polygonati Rhizoma (PR), for which rapid geographical origin identification is crucial to ensure its efficacy and product authenticity, is a traditional Chinese medicine with multiple pharmacological effects such as hypoglycemic and anti-tumor effects. This study presents a rapid identification method of sliced PR geographical origin based on auto-focus laser-induced breakdown spectroscopy (LIBS) combined with interpretable machine learning. The spectral data of sliced PR samples from 8 producing areas were obtained by using the self-built auto-focus LIBS system without further sample processing. Various data preprocessing methods, feature variable selection methods, and classification algorithms were evaluated. The results showed that the combination of wavelet transform (WT), Model-Free (MF) algorithm, and area normalization (AN) outperformed each method used individually. Among the feature selection methods, iteratively retaining informative variables (IRIV), variable iterative space shrinkage approach (VISSA), and the successive projection algorithm (SPA), the fewest feature variables were selected by SPA. However, by combining with Linear discriminant analysis (LDA), K-nearest neighbors (KNN), Multilayer perceptron (MLP), and Support vector machine (SVM), a good prediction accuracy of 95.00% was still achieved by SPA-SVM. Furthermore, according to the importance analysis by the SHapley Additive exPlanations (SHAP) algorithm, Ca was the most essential element to distinguish sliced PR samples from different geographical origins, followed by other elements in the order of Fe, Ti, Sr, C, Mn, Mg, Li, Ba, K, H, Si, and Na. This study provides a simple, rapid, and reliable analytical approach for PR authentication, which has broader applications in medicinal material and food product verification.

Abstract:Gallium is a technology-critical element whose concentration increases owing to industrial activity. To study anthropogenic contamination in maritime Antarctica (Nelson Island, South Shetland Islands), it was necessary to develop an analytical method to determine the trace Ga content in Antarctic flora. The determination of Ga using electrothermal atomic absorption spectrometry (ETAAS) is a seemingly routine analytical task; however, the commonly used atomic lines of 287.4?nm and 294.4?nm appear to be unsuitable for analytical use. In this study, the fundamental aspects of Ga determination were investigated, and an atomic line at a wavelength of 417.2?nm was recommended for the analysis of environmental samples. The Ga content in mosses, lichens, mushrooms, and grass samples from Antarctica are published here for the first time. Based on the Ga content of lichens as biomonitors of atmospheric pollution, it can be assumed that contamination of the studied locality through atmospheric deposition is low.

Abstract:Certified Reference Materials (CRMs) are a widely recognized tool for the comparability of measurements taken in different times and spaces through their “traceability chain”. However, aqueous CRMs used as calibrants which allow tracing to the SI units are urgently needed especially for the speciation analysis CRMs due to the difficulty of development and certification for them. Herein, we presented two new aqueous trimethyllead reference materials. In the certification campaign, two important steps were included: 1) a traceability chain to the standard reference material GBW08619 which is a primary Pb(II) calibrant solution was set up; 2) isotopic variations of lead in trimethyllead (TML) and GBW08619, were introduced to the certified values and combined uncertainties. This paper describes in detail the homogeneity and stability studies, impurity assessment with nuclear magnetic resonance spectroscopy (NMR) and high-performance liquid chromatography - inductively coupled plasma mass spectrometry (HPLC-ICP-MS), traceability assurance protocol and the inter-laboratory co-certification campaign for the certification of their TML contents. Consequently, two CRMs (GBW(E)080971: (92.73±3.15) μg g-1 as Pb, k=2 and GBW(E)080972: (0.740±0.030) μg g-1 as Pb, k=2) are now available.

Abstract:Zircon U-Pb geochronology has been widely used for determining the age of geologic processes. However, for very ancient zircon samples (e.g., ~3.8 Ga), the quality of U-Pb dating results may be affected by the relatively high-grade of Pb loss caused by the crystal damage through radioactive decay of U and Th. Here, we present a comparative study to explore the effect of thermal annealing (TA) and chemical abrasion (CA) on zircon U-Pb geochronology using zircon samples from some of the oldest igneous rocks on Earth (the Acasta Gneiss and the Muzidian Gneiss complexes), with the goal of getting better constrained zircon U-Pb ages of ancient rocks. Prior to the laser ablation dating experiments, all zircon samples and reference standards were thermally annealed (850 ℃ ~ 1050 ℃/48 h), and a subset of thermally annealed zircon samples was then selected for chemical abrasion treatment (partial dissolution using hydrofluoric acid at 170 ℃ for12 h), in order to remove radiation damaged domains. The results show that the U-Pb ages of CA zircon grains appear to be more concordant with smaller MSWDs than those of the TA and untreated zircon grains, indicating that the partial dissolution treatment of thermally annealed zircon grains effectively removed domains with Pb loss, leaving the rest of the zircon crystal lattice relatively unaffected. Therefore, for complex and ancient (> 3.8 Ga) zircon samples, chemical abrasion prior to laser ablation is shown to be useful for reducing Pb loss and data scatter. Thermal annealing appears to improve the matrix match between the unknown and reference zircon grains, which is especially useful for the dating of high U, young zircon samples. Additionally, our results show no systematic difference in the trace elements and Hf isotopic compositions between treated and untreated zircon samples, which demonstrates that the treatments do not have negative effect on the trace elements and Lu-Hf isotopic compositions in zircons.

Abstract:The direct determination of sulfur isotope ratios 34S/32S (δ34S), in atmospheric precipitation by triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS) is challenging owing to intense interference from polyatomic species of mass that affects all sulfur isotopes. Additionally, high background levels of sulfur often pose a challenge for accurately determining δ34S at low concentrations in atmospheric precipitation samples. To address these challenges, a reliable method based on mass shift ICP-MS/MS was developed in this study. The δ34S ratio was determined at m/z 48 and 50 instead of at m/z 32 and 34 by using O2 as a reactive gas to shift the 32,34S+ ions to 32,34S16O+, thus avoiding on-mass interferences at m/z 32 and 34. The sulfur concentration in the background blank, which mainly originated from the Ar and O2 gas used during analysis, was reduced from 22.1 μg L–1 to 0.82 μg L–1 by purifying Ar and O2 using a gas trap. The δ34S measurements were not significantly affected by the sulfur concentration of the sample between 200 and 1000 μg L–1, and the atmospheric precipitation matrix did not affect δ34S determination using ICP-MS/MS. Therefore, the proposed method does not require strict matrix and concentration matching, simplifying the analytical process. The results obtained from atmospheric precipitation using the proposed method are consistent with those obtained by isotope ratio mass spectrometry, thereby validating the proposed method.