2021, 42(6):294-298. DOI: 10.46770/AS.2021.608
Abstract:MarSCoDe (Mars Surface Composition Detector) is China's first instrument for Mars material analysis, which accompanies the Zhurong Mars rover landing on Utopia Planitia and will detect interested Martian rock and soil targets based on laser-induced breakdown spectroscopy (LIBS) technique. MarSCoDe consists of a bioxial pointing mirror (BPM), an optical head, a calibration targets assembly (CTA), a spectrometer module (SM) and a payload controller. The MarSCoDe is scheduled to analyze twelve major elements. To achieve accurate quantitative analysis and classification of Mars targets, a PSO (particle swarm optimization)-based calibration scheme is adopted to correct the spectral shift due to the temperature change on Mars, and then a convolutional neural network (CNN) was proposed to implement the analysis of elements. Finally, the mineral types of Martian objects will be identified according to the alkali silica ratio. The detection results of the MarSCoDe will provide further information about the evolution of Mars.
2021, 42(6):299-309. DOI: 10.46770/AS.2021.710
Abstract:Trends and advances in the development and application of inductively coupled plasma tandem quadrupole mass spectrometry (ICP-QMS/QMS) with a reaction cell is reviewed mainly based on publications from January 2018 to July 2021. ICP-QMS/QMS has been applied in various research fields covering the sciences of biology, energy, environmental, food/medical, geology, materials, and radionuclide. The objectives of analysis cover the determination of elemental concentration, ion-gas reaction, isotope analysis, single particle analysis, and chemical speciation analysis. Measurement of most elements in the periodic table are reported except for H, N, O, F, rare gas, and some of the radionuclides. In addition to the default reaction/collision gases (i.e., He, H2, O2, and NH3), N2O, CO2, CH4, CH3F, C2H4, and C2H6 have been used as reaction gases to improve the capability of separating spectral interferences or to study the ion-molecule reactions. Typical applications of ICP-QMS/QMS analysis in the major research fields are also discussed.
2021, 42(6):310-327. DOI: 10.46770/AS.2021.707
Abstract:Electrothermal or graphite furnace atomic absorption spectrometry (ETAAS or GFAAS) is one of the most widely used techniques for determining elements in different matrices (e.g., foodstuffs, pharmaceuticals, biological specimens, nanomaterials, polymers, fuels and environmental media). Numerous elements can be simply and quickly determined with high precision and accuracy, low detection limits, and at moderate cost. The technique is also suitable for direct solid and slurry sample analysis. A crucial feature of this technique is that it can perform simultaneous or sequential multi-element analysis. Over the years, many instruments have come on the market for multi-elemental analysis using mostly line source (LS) GFAAS and high-resolution continuum source (HR-CS) GFAAS. This review covers publications from 2000 to 2020 related to the simultaneous or sequential multi-elemental analysis by LS-GFAAS and HR-CS-GFAAS. Mainly the applications, the limits of detection, the use of internal standardization and other aspects regarding the matrix, pyrolysis and atomization temperatures and modifiers are discussed. Finally, a critical comparison is made between the LS-GFAAS and HR-CS-GFAAS techniques.
2021, 42(6):328-334. DOI: 10.46770/AS.2021.802
Abstract:The method of isotope dilution and tracing, based on ethylation-purge and trap-gas chromatography (GC)-inductively coupled plasma mass spectrometry (ICP-MS), has been widely used for the accurate analysis of methylmercury (MeHg) and for tracking its environmental fates (e.g., formation/degradation). However, the tedious ethylation derivatization and purge and trap processes limit analytical throughput. In this work, an automatic ethylation derivatization and purge and trap method, followed by GC separation, pyrolysis, and ICP-MS detection, was developed for MeHg analysis. The throughput and detection limits of this proposed method for MeHg were 7.5 min/sample and 0.03 ng L-1, respectively, with a relative standard deviation of 3.7%. The accuracy of the developed method was validated by the analysis of a spiked water sample and a certified reference material (DORM-4, Fish protein) using isotope dilution (Me201Hg). In addition, anaerobic Geobacter sulfurreducens PCA-mediated methylation of Hg2+ and demethylation of MeHg was monitored by using double-enriched isotope tracing (199Hg2+ and Me201Hg). This automatic ethylation-purge and trap-GC-ICP-MS method is promising for routine MeHg analysis with isotope dilution/tracing.
2021, 42(6):335-348. DOI: 10.46770/AS.2021.803
Abstract:U–Pb geochronology of carbonate by laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) is a rapidly growing research field due to its great potential to solve geological problems related to basin, tectonic, magmatism, and environmental evolution. In this paper, grid diagram was used to improve analytical efficiency. Two analytical modes of mixed collectors and multiple ion counting collectors were used on a Thermo Fisher Neptune Plus for carbonate U–Pb dating. Jet sample cone and X skimmer cone with Ar-N2 plasma (small addition of nitrogen into the sample gas flow) was used to enhance signal sensitivity of U and Pb. Our results showed that the sensitivity with Jet + X cones and adding nitrogen was a factor of two and eight greater than using standard sample cone and H skimmer cone in Ar-N2 plasma and Ar plasma, respectively. The fluence, repetition rate and spot size of the laser were investigated to assess effects on U–Pb results of different laser parameters. Medium energy fluences (~6 J/cm2) and medium ablation frequency (6 or 8 Hz) are suitable laser parameters for most samples to gain good U–Pb dating results for carbonate. Our new technique was evaluated by investigating five carbonate standards with U–Pb ages ranging from 2.4 to 254 Ma, in good agreement with their reference values. Our improved method was successfully applicable to date carbonate concretion, hydrothermal calcite vein, and peperite, which yielded new age results coinciding with stratigraphic relationship, structure analysis, and other dating methods.
2021, 42(6):349-358. DOI: 10.46770/AS.2021.099
Abstract:Laser-induced breakdown spectroscopy (LIBS) was applied for the characterization of the methane-air laminar diffusion flame, revealing the spatial distribution of its composition. From the measurement, it was found that distribution of the atomic and ionic N emissions produced by the flame had obvious differences, which were mainly distributed in the air area and flame area, respectively. A comparison of the LIBS spectra of air, methane gas, and methane-air laminar diffusion flame showed that the atomic N emissions were mainly produced by the excitation of N2, and the ionic N emissions were more related to the N-containing combustion products. In addition, the correlation between typical emissions and the flame temperature measured by thermocouple was estimated to show that the tendency of the changes in temperature can be characterized by C2 emission intensities. This work provides a new method for real-time online flame temperature measurement, and also provides a reference for revealing the formation process and conversion pathway of each component in the flame.
2021, 42(6):359-364. DOI: 10.46770/AS.2021.098
Abstract:Rare earth elements (REE) are important tools in geological studies. Accurate determination of REE concentrations can be affected in geological samples with low REE levels and/or high levels of interfering barium. Development of chemical separation methods allowing to isolate REE from other matrix components is a thorough approach to overcome this issue. In this study, a simple, RE resin-based separation method was developed and tested for a variety of sample solutions (mixed element solutions, shale, carbonate and granite). The method shows a good REE recovery and is efficient for the removal of matrix element, and notably Ba. The method is suitable for precise determination of the Eu contents in rock samples with high barium content.
2021, 42(6):365-373. DOI: 10.46770/AS.2021.724
Abstract:With the increasing popularity of alternative breads, investigating their health benefits and risks is vitally important. The bioaccessibility of potentially toxic elements (PETs) in these breads could indicate a potential risk to consumers. The continuous online leaching method (COLM) involves the sequential leaching of a mini-column of food by artificial saliva, gastric juice, and intestinal fluid with real time monitoring of elements being released. Because the dissolution equilibrium is shifted to the right from continuous exposure to fresh reagent, it assesses bioaccessibility in three gastrointestinal matrices in less than 30 min and includes valuable kinetic extraction information. In this study, a gluten-free (GF) and a rye bread were analyzed for As, Cd, and Pb before and after toasting. Toasting lowered all PTE concentrations by a factor of 1.5 (As in rye bread) to 2.5 (Cd in rye bread). Most of the PTEs present were bioaccessible whether the bread was toasted or not. In the case of As, a significant portion is in the form of As(III) and As(V). COLM analysis allowed for Pb sourcing, revealing two potential sources of Pb being released separately in gastric juice from rye bread based on their significantly different 206Pb/207Pb and 208Pb/206Pb isotope ratios. Comparison with Pb ratios reported in previous literature revealed that some of the gastric-mobile Pb in rye bread came from the Pb historically added to gasoline in North America. This source completely vanished upon toasting rye bread.
2021, 42(6):374-382. DOI: 10.46770/AS.2021.906
Abstract:A valid method for trace silver (Ag) detection in geological samples was developed in this study using aerosol dilution inductively coupled plasma-mass spectrometry after extraction with inverse aqua regia. This was proposed primarily to reduce the interference from Nb and Zr during mass spectrometric measurements. Almost 93% of Nb and Zr was removed after the extraction. By mixing an appropriate amount of Ar with the sample aerosol using an aerosol dilution system prior to plasma, the residual Nb oxides and Zr oxides or hydroxides could be successfully removed. The relative yields of the interfering oxides and hydroxides were as low as 0.087% (NbO/Nb) and 0.013% (ZrOH/Zr), which were 3–5 times lower than those in the traditional mode without the addition of Ar. Moreover, the signal-to-noise ratio of Ag was five times higher than that in the traditional mode. The proposed method was applied to the determination of Ag in 68 standard reference materials (SRMs) of soil, sediment, and rock. The results for 47 of these geological SRMs were in good agreement with the reference values. The Ag levels in three SRMs (GSP-2 Granodiorite, STM-2, and SGR-1b) are being reported for the first time herein. For these SRMs, 10 separate aliquots of the sample were digested and analyzed over a period of three months, and analysis revealed that the determined values were reasonable. Thus, the proposed method shows significant potential for the accurate determination of trace Ag in various geological samples.