Journal of Analytical Atomic Spectrometry最新文献

An experimental study on the packing thickness (PT) dependent plasma emission caused by laser ablating thin-layer microgranular samples in air was conducted using three sets of size-selected copper grains (median size d₅₀ = 53 μm, 72 μm, and 100 μm, respectively). For each size-selected case, the PT parameter was tuned from 0.15 to 1.00 mm through varying the amount of grains packed into a vessel with a steel bottom wall and the emission spectra of laser-induced plasma were measured at various PT. It is found that there is a striking threshold phenomenon in the measured behavior of PT-dependent plasma emission. Specifically, when PT is less than a threshold PT_th, the emission intensity exhibits an exponential decreasing with incremental thickness; however, when it exceeds PT_th, the emission intensity becomes almost constant. It is also found that the PT_th slightly depends on grain size but the ratio of PT_th to d₅₀ seems to be size independent. Combining the mechanical fundamentals of granular materials, we interpreted the findings by considering a PT-dependent effect of the vessel's bottom on the formation circumstance of a laser-induced plasma. This work has practical significance in assessing a threshold thickness above which laser-induced breakdown spectroscopy, as an analytical technique to quantify elements embedded in microgranular materials, is viable regardless of PT difference.

Chlorine isotopic ratio measurements are useful for stable isotope tracing, isotopic abundance measurements in nuclear chemistry, and accurate determination of concentrations using isotope dilution methods. Accurate and precise determination of Cl isotopic ratios using inductively coupled plasma mass spectrometry (ICP-MS) methods is challenging due to major polyatomic interferences of ¹⁶O¹⁸O¹H⁺ and ³⁶Ar¹H⁺ on ³⁵Cl⁺ and ³⁷Cl⁺, respectively. Previous work has demonstrated that using tandem mass spectrometry (ICP-MS/MS) with either H₂ or O₂ gas in the collision/reaction cell can significantly improve the precision, but not necessarily the accuracy, of chlorine isotopic measurements over single-quadrupole techniques. In this work, we further investigate ICP-MS/MS, using O₂ as a reaction gas, as a technique for accurate determination of Cl isotopic ratios. Using the methodology developed herein we measure both natural and enriched chlorine isotopic ratios in diverse samples matrices, targeting ³⁷Cl isotope enrichment efforts, without the need for complex front-end chemistry (i.e., ion exchange chromatography), while maintaining a typical accuracy and precision better than ∼1%. The reduced need for time-consuming sample processing afforded by this method results in higher sample throughput (>80 measurements/day) relative to other analytical techniques (e.g., thermal ionization mass spectrometry, accelerator mass spectrometry, etc.). This work demonstrates that ICP-MS/MS with O₂ as a reaction gas can be a useful tool for making rapid and accurate chlorine isotopic ratio measurements.

This study presents the development, validation and use of an approach for precise and accurate cadmium (Cd) isotopic analysis at low concentration levels using multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). The MC-ICP-MS unit used was equipped with a standard sample introduction system, thus using an ICP operated under wet plasma conditions, and Faraday cup amplifiers equipped with a 10¹³ Ω resistor. One-column anion exchange chromatography allowed isolation of Cd with 80–99% recovery and absence of an effect of potential on-column fractionation on the isotope ratio results was demonstrated. Use of both an internal (using Ag) and an external (measured in a sample-standard bracketing sequence) standard was relied on for correction of the bias introduced by instrumental mass discrimination. A long-term precision of 0.09‰ (2SD) for δ^114/110Cd was achieved at a Cd concentration of 10 ng mL⁻¹. The method developed was validated by analysing NIST SRM 2711a (Montana soil) and NRC TORT-3 (Lobster hepatopancreas) reference materials, yielding results consistent with literature values. Subsequently, the method was applied to two Antarctic marine organisms Adamussium colbecki and Trematomus bernacchii, collected during both the 1990s and 2020s, to investigate its potential for identifying changes in the biogeochemical cycle of Cd over time and reveal natural or anthropogenic sources. A preferential uptake of the lighter Cd isotopes in both species was observed, indicated by negative δ^114/110Cd values ranging between −0.24 and −0.09‰. This finding is consistent with previous studies that have reported Cd fractionation during its uptake by marine organisms, with a preference for the lighter isotopes. No significant differences in δ^114/110Cd values were observed between organs of the same species or between the same species collected in the different decades, suggesting minimal Cd isotope fractionation during internal transfer and consistent Cd sources over time. Comparison with literature data suggests that the Cd source in Antarctic biota may be predominantly of natural origin, with δ^114/110Cd values indicating isotopically heavier Cd than that found in Cd-polluted areas. However, further Cd isotope ratio data from various Antarctic sample types are necessary to further evaluate the Cd sources in marine samples.

In situ U–Th–Pb geochronology of monazite is widely used to reveal geological histories. Well characterized matrix-matched reference materials are crucial for achieving accurate results in microbeam U–Th–Pb dating. In this paper, the internal structure, chemical composition and U–Th–Pb dates of M6 monazite are investigated using multiple analytical methods to evaluate its potential as a reference material for in situ monazite U–Th–Pb dating. The results show that M6 monazite has an average ThO₂ content of 10.7 ± 1.1% (2SD; SD = standard deviation) and Th/U ratio of 28.4 ± 3.3 (2SD). In situ U–Th–Pb dates from laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and secondary ion mass spectrometry (SIMS) laboratories are reproducible and homogeneous at the spatial level of 30 μm. Seven ²⁰⁷Pb/²³⁵U dates from isotope dilution-thermal ionisation mass spectrometry (ID-TIMS) yield a mean date of 485.7 ± 2.3 Ma (2SD), which is our recommended date for M6 monazite. Furthermore, SIMS oxygen isotope determinations show good measurement reproducibility (7.70‰ ± 0.41‰, 2SD) and the LA-MC-ICP-MS analyses yield homogeneous Sm–Nd isotopic composition (¹⁴³Nd/¹⁴⁴Nd = 0.511829 ± 0.000045, 2SD; ¹⁴⁷Sm/¹⁴⁴Nd = 0.2302 ± 0.0139, 2SD), demonstrating that M6 monazite has the potential to be a reference material for in situ O and Sm–Nd isotopic analyses.

In this work, we present a study aimed at the statistical distribution of characteristic signals of laser-induced plasmas. This work mainly focuses on observing statistical distribution for repetitive measurement of spectra, plasma plume imaging, and sound intensity. These were captured by using various laser irradiances, spanning between 1.72 and 6.25 GW cm⁻² for a 266 nm laser. Their distributions were fitted by Gaussian, generalized extreme value (GEV), and Burr distributions, as typical representation models used in LIBS. These were compared using the Kolmogorov–Smirnov (KS) test by its null hypothesis on whether these models are suitable or fail to describe the statistical distribution of the data. The behavior of the data distribution has shown a certain connection to the plasma plume temperature. This was observed for all the used ablation energies. Performances of the statistical models were further compared in the outlier filtering process, where the relative standard deviation of the filtered data was observed. The results presented in this work suggest that an appropriate selection of a statistical model for the data representation can lead to an improvement in the LIBS performance.