2022, 43(2):99-106. DOI: 10.46770/AS.2021.1110
Abstract:Here we report the Si isotope compositions of four potential reference materials, including one fused quartz glass (Glass-Qtz), one natural quartz (Qinghu-Qtz), and two natural zircons (Qinghu-Zir and Penglai-Zir), suitable for in-situ Si isotopic microanalysis. Repeated SIMS (Secondary Ion Mass Spectrometry) analyses demonstrate that these materials are more homogeneous in Si isotopes (with the spot-to-spot uncertainty of 0.090-0.102‰), compared with the widely used NIST RM 8546 (previously NBS-28) quartz standard (with the spot-to-spot uncertainty poorer than 0.16‰). Based on the solution-MC-ICP-MS determination, the recommended ??30Si values are ?0.10 ± 0.04 ‰ (2SD), ?0.03 ± 0.05 ‰ (2SD), ?0.45 ± 0.06 ‰ (2SD), and ?0.34 ± 0.06 ‰ (2SD), for Glass-Qtz, Qinghu-Qtz, Qinghu-Zir, and Penglai-Zir, respectively. Our results reveal no detectable matrix effect on SIMS Si isotopic microanalysis between the fused quartz glass (Glass-Qtz) and natural quartz (Qinghu-Qtz) standards. Therefore, we propose that this synthetic quartz glass may be used as an alternative, more homogenous standard for SIMS Si isotopic microanalysis of natural quartz samples.
2022, 43(2):107-116. DOI: 10.46770/AS.2021.827
Abstract:Incidental ingestion of soil containing Cr, As, Cd, Sb, and Pb has been attracting global attention as it can significantly impact human health. Many bioaccessibility methods have been developed to simulate the amount of contaminants extracted by gastrointestinal fluids following incidental ingestion. Although the continuous online leaching method (COLM) offers various advantages over conventional batch bioaccessibility methods, such as reduced analysis time, elemental source apportionment, and isotopic analysis, it has not yet been applied to soil and directly compared to validated, published methods. This study uses the COLM with simulated gastrointestinal fluids from the United States Environmental Protection Agency (US EPA), United States Pharmacopeia (USP), and unified bioaccessibility method (UBM) to measure the bioaccessibility of Cr, As, Cd, Sb, and Pb in NIST 2710, NIST 2710a, NIST 2711a, and BGS 102. When the US EPA gastrointestinal fluid was used, no significant difference was observed between the COLM bioaccessible + residual, aqua regia extraction, or certificate concentrations for all the elements and soils studied. Furthermore, COLM bioaccessibility was within the acceptable range of control limits and bioavailability (animal) studies for most reference materials. In addition, no statistically significant difference was observed between either the US EPA batch method or the stomach phase of the UBM batch method and the stomach stage of the COLM, indicating that the COLM could be incorporated into current bioaccessibility analyses to improve soil contamination characterization in the future.
2022, 43(2):117-125. DOI: 10.46770/AS.2021.910
Abstract:This study proposes a highly efficient method for the direct determination of Zn isotopes in Zn-rich minerals, without the use of column chromatography, via multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Experiments (with or without column chromatography) were performed to evaluate the feasibility of directly obtaining non-deviated Zn isotopic ratios by MC-ICP-MS. For Zn isotopes determined without the use of column chromatography, the instrumental mass bias was corrected using the standard sample bracketing with Cu as the internal standard. The effects of acidity and concentration mismatch and the matrix effect were strictly assessed in a wet-plasma mode. The Long-term reproducibilities of δ66Zn and δ67Zn better than ± 0.03‰ (n = 42, 2 standard deviations (2s)) and ± 0.05‰ (n = 42, 2s), respectively, were achieved by repeatedly measuring the NIST Standard Reference Materials (SRM) 682 solution doped with trace matrix elements over four months. Zn-rich minerals determined without employing column chromatography displayed little drift in δ66Zn and δ67Zn values compared with minerals determined using column chromatography, with Δ66Znwithout?with (Δ66Znwithout-with = δ66Znwithout - δ66Znwith) ranging from -0.04 to +0.01‰ and Δ67Znwithout?with ranging from -0.06 to +0.01‰. These results suggest that non-deviated Zn isotopic ratios in Zn-rich minerals can be achieved without column chromatography due to the low contents of undesired matrix elements.
2022, 43(2):126-133. DOI: 10.46770/AS.2021.607
Abstract:Direct current glow discharge mass spectrometry (dc-GDMS), which relies on sector field mass analyzers, is not commonly used for depth profiling applications because of its slow data acquisition. Nevertheless, dc-GDMS has good reproducibility and low limits of detection, which are analytical features that are encouraging for investigating the potential of dc-GDMS for depth profiling applications. In this work, the diffusion of traces of chromium and nickel was profiled at the interface of a steel-aluminum bilayer using a new sensitive dc-GDMS instrument. The depth profile of the non-treated sample was compared with that of a heat-treated specimen at 400°C for 30 min. Scanning electron micrographs, energy dispersive X-ray spectroscopy (EDS), and electron probe microanalysis (EPMA) were used to study the diffusion process. The results of the study show that both chromium and nickel are enriched at the steel-aluminum interface, with higher concentrations of both elements for the heat-treated specimen. Two peaks for both chromium and nickel were clearly present at the interface, with a high concentration of chromium in the aluminum layer. This observation is likely a consequence of elemental diffusion from the interface towards the aluminum layer. The presence of the third layer, steel beneath the aluminum layer, might also have contributed to this observation.
2022, 43(2):134-144. DOI: 10.46770/AS.2022.033
Abstract:A well-formed natural zircon crystal ~10 g in weight from Sri Lanka was introduced as a reference material for the geochemical microanalysis of U–Pb–O–Hf isotopes. For the U–Pb system, a total of 96 secondary ion mass spectrometry (SIMS) and 174 laser-ablation inductively coupled plasma mass spectrometry analyses showed that zircon ZS was homogeneous within a ~20 μm area level. According to chemical abrasion isotope dilution thermal ionization mass spectrometry, the U–Pb system is concordant within the uncertainties, yielding a weighted mean 206Pb/238U age of 560.6 ± 1.3 Ma (2 standard deviation (SD), n = 18) and a weighted mean 207Pb/206Pb age of 561.1 ± 3.5 Ma (2SD, n = 18). The U and Th concentrations were 570 ± 40 μg g-1 (1SD) and 132 ± 28 μg g-1 (1SD), respectively. The homogeneity of the O isotopes was confirmed by 261 SIMS analyses, and that of Hf isotopes was determined by 100 laser-ablation multi-collector inductively coupled plasma mass spectrometry (MC–ICP–MS) analyses. A weighted mean δ18O value of 13.69‰ ± 0.11‰ (2SD, n = 12) obtained by laser fluorination isotope ratio mass spectrometry (IRMS) and a weighted mean 176Hf/177Hf value of 0.281668 ± 0.000010 (2SD, n = 7) by solution MC–ICP–MS are recommended as the best reference values for zircon ZS.
2022, 43(2):145-153. DOI: 10.46770/AS.2021.1109
Abstract:Cadmium isotope fractionation is a promising indicator for tracing the source, transport, and transformation of Cd in the environment; therefore, a high-precision method for the Cd isotope analysis of environmental samples is urgently required. In this study, eight environmental reference materials (NIST 2711a, GSS-1, GSS-4, GSS-5, GSD-11, GSD-12, GSD-30, and BCR-679) with different matrices were digested under microwave irradiation and purified via anion exchange. Thereafter, their Cd isotope ratios were analyzed using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) with double-spike correction. The samples digested under microwave irradiation exhibited high Cd recovery (> 96%). One step of anion-exchange-based purification can remove most interfering elements without any detectable loss of Cd. If the purified solution contained Zn/Cd > 0.04, Zr/Cd > 0.01, Mo/Cd > 0.2, Pd/Cd > 4 × 10?5, In/Cd > 0.02, or Sn/Cd > 0.1, a secondary step using the same purification procedure would be necessary. The measured δ114/110Cd values of reference materials (from ?0.558 to 0.550‰) were in adequate agreement with those of previous studies, suggesting that this method can be used to analyze the Cd isotope ratios in soil, sediment, and plant samples. In addition, the large variation in the Cd isotope ratios of these reference materials implies that the Cd isotope ratio is promising for identifying pollution sources and the biogeochemical cycle of Cd.
2022, 43(2):154-163. DOI: 10.46770/AS.2022.099
Abstract:Rapid and accurate analysis of the coal properties is essential for its clean and efficient utilization. However, the complexity of the physical-chemical characteristics of coal complicates accurate quantification of its properties using rapid spectroscopic technologies. Herein, a synergistic method is proposed to achieve optimum results for coal proximate analysis using spectra obtained via laser-induced breakdown spectroscopy (LIBS) and near-infrared reflectance spectroscopy (NIRS). Firstly, the ash content was analyzed by LIBS, and the moisture content was analyzed by NIRS. The calorific value and volatile content were then analyzed using the fusion data obtained from LIBS and NIRS, combined with the ash and moisture results. Finally, the fixed carbon content was calculated by subtracting the mass percentage fractions of ash, moisture, and volatile matter from 100%. The results indicated that the proposed method achieved good quantitative performance for coal proximate analysis. The root mean square errors of prediction for ash, moisture, calorific value, volatile matter, and fixed carbon were 0.743%, 0.304%, 0.187 MJ/kg, 0.662% and 0.972%, respectively. Thus, we believe that the proposed method based on the synergy of LIBS and NIRS opens avenues for efficient prospective analysis of coal properties.
2022, 43(2):164-173. DOI: 10.46770/AS.2022.062
Abstract:Herein we report procedures based on multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) for high-precision Fe isotopic analysis using a 57Fe-58Fe double spike technique. Iron purification was achieved using AG1-X8 in HCl media following previously or newly established procedures. In the new procedure, smaller columns with 4 mm diameter were used, containing 0.4 mL AG1-X8, thus greatly reducing the operation time and the amount of acid and resin consumed compared to the previously established method using 1 mL resin. Potential trace Ni interference on 58Fe was suppressed by increasing the total Fe ion intensity to ≥ 120 V. Measurements of GSB Fe solutions doped with mono-elements demonstrated that a mass bias correction by the 57Fe-58Fe double spike was robust if Ca/Fe ≤ 1.0, Al/Fe ≤ 1.0, Cu/Fe ≤ 1.0, Co/Fe ≤ 0.1, Ni/Fe ≤ 10-4, and Cr/Fe ≤ 10-4. Monitoring of pure Fe standard solutions, viz. IRMM-014 and NIST3126a, and geological reference materials, viz. JP-1, BHVO-2, W-2a, GSP-2, and COQ-1, over nine months yielded δ56Fe (relative to IRMM-014) values of 0.003 ± 0.013‰ (2 SD, N = 20), 0.368 ± 0.011‰ (2 SD, N = 30), 0.019 ± 0.018‰ (2 SD, N = 15), 0.109 ± 0.017‰ (2 SD, N = 30), 0.049 ± 0.018‰ (2 SD, N = 17), 0.155 ± 0.018‰ (2 SD, N = 14), and -0.066 ± 0.022‰ (2 SD, N = 20), respectively, consistent with the recommended values within quoted errors. Based on repeated analyses of the standards, the long-term precision of our double spike method is better than 0.02‰ for δ56Fe on average, proving its ability to distinguish small isotope fractionation among high-temperature samples.
2022, 43(2):174-185. DOI: 10.46770/AS.2021.609
Abstract:The aim of this review is to provide a brief introduction to recent research advances in in-situ online detection of atmospheric pollutants based on laser-induced breakdown spectroscopy (LIBS) under atmospheric environments. Atmospheric pollution has drawn much public attention, and there is increasing demand for rapid and accurate evaluation of atmospheric environments. LIBS has the advantages of in-situ online detection, simultaneous multi-element analysis, and noncontact measurement, making it a highly competitive analytical technique in the field of environmental monitoring. In terms of the different target samples, some typical research cases, including atmospheric particulate matter, atmospheric pollution sources, halogens in VOCs, atmospheric sulfur, and stable isotope abundance, are presented to illustrate the current development and problems of LIBS detection in this field.
2022, 43(2):186-200. DOI: 10.46770/AS.2021.912
Abstract:Electron probe microanalysis (EPMA) is an in-situ and non-destructive analytical technique with high spatial resolution and an increasingly important analysis tool in materials science and geosciences. This study summarizes the principles and functions of EPMA, and the problems and difficulties, along with the recent advances in quantitative analysis of EPMA. A routine EPMA procedure includes preparing samples, setting analytical conditions, acquiring data, and evaluating results. Caution is required in all steps to obtain high-quality analytical results. The problems and difficulties commonly encountered in EPMA are discussed and the corresponding measures and solutions required to resolve them are proposed. Specific analytical methods are suggested to make accurate analysis of some specific minerals. We also summarized the challenges and solutions in light element analysis, trace element analysis, EPMA U-Th-Pb total dating, combined analysis with wavelength- and energy-dispersive X-ray spectroscopy, submicron spatial resolution analysis at low accelerating voltages, iron oxidation state analysis, and standard reference materials.