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  • 1  Quantitative Analysis of Gold Nanoparticles in Single Cells with Time-resolved ICP-MS
    Jinhui Liu Lingna Zheng Junwen Shi Xing Wei Xue Li Mingli Chen Meng Wang Jianhua Wang Weiyue Feng
    2021, 42(3):114-119. DOI: 10.46770/AS.2021.102
    [Abstract](286) [HTML](0) [PDF 4.24 M](6957)
    Abstract:
    Single-cell inductively coupled plasma mass spectrometry (SC-ICP-MS) has been introduced for the analysis of intracellular essential elements and nanoparticles (NPs) at the single cell level. However, it is still quite challenging for accurate and reliable determination. In this work, a high-efficiency sample introduction system was used for single cell analysis with ICP-MS. The system includes a microconcentric nebulizer, a low-volume single pass spray chamber, and a syringe pump. The transport efficiency of single cells was greatly improved to ~12%. In addition, 197Au signals in individual HepG2 cells, after incubation with gold nanoparticles (AuNPs) at the concentrations of 0.1, 0.5, and 1 μM for 12 h, were analyzed by time-resolved ICP-MS with dwell times of 100 μs and 5 ms, respectively. The 197Au signal-to-background ratio (S/B) at 100 μs dwell time was much higher than at 5 ms. For quantitative analysis, AuNP standard reference materials were used for calibration. The SC-ICP-MS data using NP calibration were in good agreement with those using solution ICP-MS analysis, validating the developed SC-ICP-MS method.
    2  Design, Function, and Implementation of China's First LIBS Instrument (MarSCoDe) on the Zhurong Mars Rover
    Xiong Wan Chenhong Li Hongpeng Wang Weiming Xu Jianjun Jia Yingjian Xin Huanzhen Ma Peipei Fang Zongcheng Ling
    2021, 42(6):294-298. DOI: 10.46770/AS.2021.608
    [Abstract](438) [HTML](0) [PDF 14.32 M](5946)
    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.
    3  Temperature Difference Between Gas Species in Absorption Measurements Using Diode Laser Absorption Spectroscopy and Its Effect on Temperature Reduction
    Akira Kuwahara Yasuaki Aiba Takuya Nankawa Makoto Matsui
    2021, 42(3):134-140. DOI: 10.46770/AS.2021.006
    [Abstract](152) [HTML](0) [PDF 2.25 M](5292)
    Abstract:
    The observation of isotope shifts due to a difference in mass number by diode laser absorption spectroscopy (DLAS) is a powerful approach for the isotope analysis of radionuclides. The spectral resolution for the detection of slight shifts can also be enhanced by a temperature reduction using adiabatic expansion. In our previous studies, we reported that the translational temperature was successfully decreased to approximately 180 K in xenon isotope analysis using a supersonic plasma jet. However, there remains a considerable uncertainty regarding the significant temperature reduction compared with the temperature of argon atoms at the edge of the supersonic plasma jet, which is at 790 K. In this study, temperature differences between two species of three mixed gas patterns (neon/argon, argon/strontium, and argon/xenon) were investigated using low-pressure glow discharge plasma. The temperature differences for the mixed gas patterns were clearly observed and are sufficient evidence to support our previous results. The relationship between temperature differences and energy levels of lower states used as absorption transitions is also discussed.
    4  In situ Investigation of the Valence States of Iron-bearing Phases in Chang’E-5 Lunar Soil using FIB, AES, and TEM-EELS Techniques
    Bing Mo Zhuang Guo Yang Li Dan Zhu Xiaojia Zeng Xiongyao Li Jianzhong Liu Yanxue Wu
    2022, 43(1):53-59. DOI: 10.46770/AS.2022.014
    [Abstract](575) [HTML](0) [PDF 4.58 M](5228)
    Abstract:
    Nanophase iron (np-Fe0) is a major product of space weathering and its presence significantly alters the reflectance spectral characteristics of lunar soil. Previous studies have established that the np-Fe0 particles originate from the reduction of ferrous ions in the plasma, in-situ decomposition of olivine and pyroxene, and disproportionation of ferrous ions in solid ferrosilicates. In this study, sample charging effects were eliminated and in situ nanoscale valence state analysis of iron-bearing phases in Chang’E-5 lunar soil was conducted by combining focused ion beam (FIB) microscopy, Auger electron spectroscopy (AES), and transmission electron microscopy-electron energy loss spectroscopy (TEM-EELS) techniques. The results indicate that the contents and valence states of iron in the np-Fe0 particles, amorphous matrix, and ferrosilicates differ. The np-Fe0 particles were found to be composed of pure metallic iron, whereas ferrous and ferric iron ions were present in olivine crystals and the amorphous matrix, respectively. The discovery of both metallic and ferric iron in the amorphous matrix of Chang’E-5 lunar soil offers new insights regarding the disproportionation reaction of Fe2+ on the lunar surface. This study demonstrates that the combination of FIB, AES, and TEM-EELS is an effective and precise approach for analyzing the valence states of iron-bearing phases in lunar soil, which can be extended to other extraterrestrial samples and other multivalent elements.
    5  Accurate Measurement of Chromium Isotopic Compositions in Geological Reference Materials by Double-Spike MC-ICP-MS
    Kai Shi Guangliang Wu Jian-Ming Zhu Xiangli Wang
    2021, 42(3):128-133. DOI: 10.46770/AS.2021.008
    [Abstract](171) [HTML](0) [PDF 1.82 M](5021)
    Abstract:
    The δ53/52Cr values of twenty-five geological reference materials (GRMs) were determined including igneous rocks, coal, shale, stream/ocean sediments and soils, with high-precision double spike MC-ICP-MS (Neptune Plus). Previously measured GRMs, including MUH-1, OKUM, DTS-2B, and JB-3, were used to monitor the long-term analytical precision and accuracy. The resulting method yielded a long-term precision of ≤ 0.06‰ based on these GRMs, and the δ53/52Cr values were excellently consistent with their previously reported values. Most of the seventeen new GRMs reported here yielded δ53/52Cr values within a narrow range from -0.20‰ to 0.01‰, with an average of -0.14 ± 0.10‰(2SD), which was the same as the unfractionated Bulk Silicate Earth (BSE). However, SCO-2 (shale) yielded a δ53/52Cr value of 0.19 ± 0.03‰ (2SD) and GBW07334 (ocean sediment) yielded a δ53/52Cr value of 0.01 ± 0.05‰ (2SD), which were different from the BSE. Thus, SCO-2 and JH-1 (-0.20 ± 0.02‰) can serve as good candidate GRMs for interlaboratory comparisons.
    6  Concentrations of Total As and As Speciation in Chinese Rice Wine and Associated Risk Assessment in Main Producing Provinces
    Yatao Huang Ningyu Lei Xuefei Mao Min Wang Christophe Blecker Philippe Maesen Bei Fan Fengzhong Wang
    2021, 42(3):141-147. DOI: 10.46770/AS.2021.017
    [Abstract](161) [HTML](0) [PDF 2.25 M](4992)
    Abstract:
    Rice and rice products have been identified as significant sources of As. Concerns have been raised about the presence of As in rice wine. This study collected 79 rice wine samples from China. High-performance liquid chromatography-inductively coupled plasma mass spectrometry was used to determine total As and As species concentrations. The average concentration of total As was 14.6 μg L-1, and the concentration of As (III) (arsenite), As (V) (arsenate), dimethylarsinic acid (DMA), and arsenobetaine (AsB) were 2.86 μg L-1 (0.970–6.08 μg L-1), 7.22 μg L-1 (2.24–22.9 μg L-1), 3.92 μg L-1 (1.58–7.82 μg L-1) and 0.620 μg L-1 (ND-0.950 μg L-1), respectively. MMA (monomethylarsonic acid) and AsC (arsenocholine) were not detected. The THQs (target hazard quotients) for chronic noncarcinogenic risks (skin lesions as the point of departure) were below 1, suggesting that the Chinese population did not encounter a significant noncarcinogenic risk. However, the mean values of MOE (margin of exposure) for lung cancer were below 100 (62.1 to 75.1) for male drinkers, indicating a potential carcinogenic risk. By comparing the As species of rice wines and the main raw material, it was found that the methylation increased DMA during fermentation.
    7  In Situ Micro-XRD Methods for Identifying Glass and Minerals in Extraterrestrial Samples
    Jiaxin Xi Lingya Ma Haiyang Xian Gaofeng Wang Jieqi Xing Jingming Wei Jianxi Zhu Hongping He
    2022, 43(1):19-27. DOI: 10.46770/AS.2022.016
    [Abstract](159) [HTML](0) [PDF 8.97 M](4962)
    Abstract:
    Glass or amorphous state materials are vital components of lunar regolith and have attracted considerable attention. The analytical data on the texture and structure of glassy and crystallized materials can be used to reconstruct the geological history of the Moon. However, it is often challenging to distinguish glass from crystals based on morphology and elemental composition, especially in complex extraterrestrial samples that have been subjected to significant impact and metamorphism. In this study, micro-X-ray diffraction (μXRD) techniques were used to identify crystalline minerals and glassy phases in lunar breccia samples extracted in the Chang'e-5 mission. The samples were processed using different operating methods to identify a technique that would minimize damage to their original appearance and structure and yield optimal results. The diffraction results, which possessed two-dimensional patterns were classified into dominant dispersion halos, concentric diffraction rings, independent diffraction spots, and coexisting rings and spots. The results correspond to four types of sample states, namely, the amorphous material, polycrystal, single crystal, and a mixture of polycrystals and single crystals. By identifying the crystallization state and phases of various samples in a non-destructive and intuitive manner, μXRD can facilitate in situ analysis of special samples generated during important geological events, thereby promoting the understanding of complex origins and evolution of extraterrestrial bodies.
    8  Protected Geographical Identification of Honey by Spark Discharge-assisted Laser-induced Breakdown spectroscopy (LIBS)
    Diana Corina Fechner Tiago Var?o Silva Maurilio Gustavo Nespeca Alan Lima Vieira José Anchieta Gomes Neto Dário Santos Júnior Roberto Gerardo Pellerano Edilene Cristina Ferreira
    2021, 42(3):148-153. DOI: 10.46770/AS.2021.022
    [Abstract](162) [HTML](0) [PDF 3.84 M](4800)
    Abstract:
    Honey is a natural food that is valued worldwide for its nutritional and therapeutic values. Therefore, authentication of honey according to the geographical origin is a guarantee of the genuine properties. In this article, an evaluation of spark discharge-assisted laser-induced breakdown spectroscopy (SD-LIBS) for certification of the geographical origin of honey is reported. Forty-nine samples of multifloral honey produced in four Argentine provinces were considered. The results showed the best classification performance was obtained using smoothing, generalized least squares weighting (GLSW) and mean centering for spectral preprocessing, added to the k-nearest neighbor (k-NN) or Support Vector Machine (SVM) classification algorithms, which provided 100% of correct classification. More importantly, the results of Partial Least Squares – Discriminant Analysis (PLS-DA) pointed to N, Ca, K, Cu, Fe and Mn as key elements for the certification of geographical origin. In addition, the greatest potential of N stands out for the discrimination of the origin of honey. These findings confirm SD-LIBS as a promising tool for authentication of honey quality, providing a simple, fast and environmentally friendly solution. The method can be useful for industry, the market and others related to food authenticity.
    9  Simultaneous in-situ determination of major, trace elements and Fe3+/∑Fe in spinel using EPMA
    Lihui Jia Yi Chen Qian Mao Di Zhang Jiangyan Yuan Xiaoguang Li Shitou Wu Danping Zhang
    2022, 43(1):42-52. DOI: 10.46770/AS.2022.002
    [Abstract](220) [HTML](0) [PDF 5.44 M](4738)
    Abstract:
    Spinel, an important mineral in basalts and ultramafic rocks on Earth, Mars, and the Moon, is sensitive to petrologic and geochemical processes, and redox evolution. Due to the small grain size of extraterrestrial samples, investigations on the composition of spinel samples including presence of trace elements and ferric iron have been hindered by the lack of appropriate in-situ analytical techniques with high spatial resolution and the shortage of reference materials. This paper presents a combined method of simultaneously measuring the major and trace elements, and Fe3+/∑Fe ratio in spinel samples using electron probe microanalysis (EPMA). Our new EPMA method is performed under double beam condition at a beam current of 200 nA for trace elements (Ti, V, Mn, Co, Ni, and Zn) and 60 nA for major elements (Mg, Fe, Al, and Cr) with an acceleration voltage of 25 kV. In addition, large analyzing crystals and peak overlap corrections were applied to reduce the detection limits and improve the analytical precision. The detection limits of 16–55 μg/g (3σ) for trace elements were achieved, and the estimated accuracies for the major elements and trace elements were within ± 2 and ± 6% (1σ), respectively. We selected seven spinel samples from the Luobusha and Stillwater intrusions to evaluate the validity of our method. They were sufficiently homogeneous with a relative standard deviation (RSD) of ± 2.0% (1σ) for the major elements (except MgO in 16SW3-9) and ± 7.0% (1σ) for the trace elements. The EPMA results obtained for the major and trace elements of the most homogeneous spinel LBS13-04 were compared with those measured using X-ray fluorescence and laser ablation inductively coupled plasma mass spectrometry. These values were in good agreement with the uncertainty of the methods. Thus, this spinel is highly suitable as a reference material for in situ microanalysis. The Fe3+/ΣFe ratios of high Cr# (57.7-79.1) spinel standards determined using M?ssbauer spectroscopy varied from 0.07 to 0.27, which were used for secondary standard calibration method to determine the spinel Fe3+/ΣFe ratio with an accuracy of < ± 0.04 (2σ). Our results offer a high-precision EPMA method that can simultaneously determine the major and trace elements together with the Fe3+/ΣFe ratio in spinel. This method provides robust and precise data on spinel for small, precious, and rare terrestrial or extraterrestrial samples, which can be used to understand the formation and evolution of rocky planets.
    10  Elemental Imaging of Alumina Ceramic Tube Using Laser Ablation- Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS)
    Qing Li Yan Fang Jianghua Liu Chengrong Zhang Zheng Wang
    2021, 42(3):154-159. DOI: 10.46770/AS.2021.019
    [Abstract](178) [HTML](0) [PDF 2.70 M](4720)
    Abstract:
    Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is an attractive analytical technique for the direct analysis of samples found in the geology, biology, and the environmental and material sciences. However, few reports have discussed the difficulty found in the analysis of curved surface samples by LA-ICP-MS where the main focus is on the curved surface. In this work, LA-ICP-MS was used to map the elemental images of curved surface samples by segmentation and recombination. In addition, the influence of parameters, such as laser spot size, laser fluence, repetition rate, scan speed, dwell time and washout time on lateral resolution were investigated. The developed method was applied to the imaging analysis of lanthanum in an alumina ceramic tube, and the results showed that lanthanum was not uniformly distributed in the tube.
    11  Quantitation and Imaging Analysis of Biological Samples by LA-ICP-MS
    Jianzong Zhou Xin Ni Jiangbin Fu Yatai Li Wei Guo Lanlan Jin Yue’e Peng Shenghong Hu
    2021, 42(4):210-216. DOI: 10.46770/AS.2021.068
    [Abstract](181) [HTML](0) [PDF 4.30 M](4668)
    Abstract:
    Analysis of the elemental abundance and distribution in biological tissues by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) adds to clarifying the basic questions of metabolic research and enables bioaccumulation and bioavailability studies in ecological and toxicological risk assessment. In this work, a method based on matrix-matched gelatin calibration LA-ICP-MS for the determination of essential and toxic elements in biological samples was developed. By using a mold-prepared procedure, the elemental inhomogeneity distributions in the synthesized gelatin gels were improved, which was verified by using the 3D (surface- and depth-mapping) LA-ICP-MS protocols. The limits of detection (LODs) ranged from 0.014 μg g?1 (Ba) to 48 μg g?1 (K). The results of the analysis of biological reference materials (RMs) were in good agreement with the certified values. Furthermore, a reliable bio-mapping LA-ICP-MS method is proposed for studying the metabolism of heavy metals in rat liver injected with CdS/PbS quantum dots. Our results show that the high concentration of Pb and Cd co-exist (positive correlation as high as 78%) in hepatocytes and sinusoids, which indicates that the PbS/CdS quantum dots are not dissociated into toxic heavy metal ions (i.e., Pb2+, Cd2+) in the metabolic process of the liver.
    12  High-precision Measurement of Trace Level Na, K, P, S, Cr, and Ni in Lunar Glass Using Electron Probe Microanalysis
    Di Zhang Yi Chen Wei Yang John H. Fournelle Jianglong Ji Bin Su Qian Mao Lihui Jia Jiangyan Yuan Xiaoguang Li
    2022, 43(1):28-41. DOI: 10.46770/AS.2022.001
    [Abstract](137) [HTML](0) [PDF 5.31 M](4517)
    Abstract:
    Lunar glass can provide critical information on the genesis of lunar rocks and the evolution of the Moon's interior. Several minor and trace elements in lunar glass, such as Na, K, P, S, Cr, and Ni, can be measured by electron probe microanalysis (EPMA) and are informative for understanding glass type, impact volatilization, and magmatic evolution processes. However, the analytical accuracy and precision of these trace-level elements in glass can be impeded by beam sensitivity, peak shift of X-ray and secondary fluorescence effects. Using EPMA, we constructed an optimized analytical method with high accuracy and precision to analyze trace elements simultaneously with major elements in lunar glass. The method was developed using the CAMECA SXFive EPMA at the Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS). The optimal analytical conditions for Na, K, P, S, Cr, and Ni in lunar glass were as follows: 20 kV accelerating voltage, 100 nA beam current, 10 μm beam diameter, linear background mode, using large-area analytical crystals and aggregate counting strategy and a 10-min total counting time. Replicate analyses on basalt and komatiite glass standards show that the analytical results are consistent with the reference values. Variations in the levels of the analyzed trace elements fall within ± 10%. The detection limits (3σ) for Na, K, P, S, Cr, and Ni can be lowered to 17-96 ppm. Our method can prohibit sample damage of lunar glass even after a 10-min analysis time. Therefore, this optimized method can provide precise trace and major element analysis of lunar glass and help to trace its origin.
    13  Accurate analysis of Fe isotopes in Fe- dominated minerals by excimer laser ablation MC-ICP-MS on wet plasma conditions
    Kaiyun Chen Honglin Yuan Zhi’an Bao Nan Lv
    2021, 42(5):282-293. DOI: 10.46770/AS.2021.703
    [Abstract](211) [HTML](0) [PDF 4.40 M](4474)
    Abstract:
    The Fe isotope ratios can be a useful tracer of geochemistry, biogeochemistry, and the environmental redox state. In this study, we investigated the feasibility of Fe isotopic analysis in Fe-dominated minerals by 193 nm excimer ns laser ablation combined with Nu Plasma 1700 high resolution MC-ICP-MS without matrix-match calibration. Several important instrument parameters were investigated, such as the effect of the addition of nitrogen gas and water vapor, the effects of analytical parameters such as ablation mode, laser fluence, pulse repetition rate, spot size on Fe isotopic mass bias during analysis were investigated as well. The results showed that the effects of ablation mode, spot size, laser pulse repetition rate, and line scan speed can be neglected, while laser fluence and matrix effects had significant influence on the Fe isotopic mass bias at dry plasma condition. These problems can be minimized using consistent lower fluence (1.5?3.5 J·cm-2), as well as the wet plasma conditions can significantly reduce the matrix effect in Fe isotopic analysis. Fortunately, with the water vapor and nitrogen gas addition after the ablation cell, an accurate and precise Fe isotope in pyrite, manganite, hematite, and chalcopyrite analysis by ns-LA-MC-ICP-MS can be achieved with non-matrix-matched calibration. The obtained accuracy and reproducibility of the in situ determinations of δ56FeIRMM-014 were both better than ± 0.10‰ (2 SD). This study indicated that there was a serious matrix effect in the Fe isotopic analysis of Fe-dominated minerals by ns- LA-MC-ICP-MS, and nitrogen gas mixed with water vapor-assisted ns- LA-MC-ICP-MS were an appealing option for the in situ Fe isotope analysis of Fe-dominated minerals with non-matrix-matched calibration.
    14  Rapid analysis of 129I in natural water samples using accelerator mass spectrometry
    Mengting Zhang Xiaolin Hou Zhiyong Zhang Luyuan Zhang Ning Chen Miao Fang
    2021, 42(4):190-196. DOI: 10.46770/AS.2021.071
    [Abstract](137) [HTML](0) [PDF 2.23 M](4470)
    Abstract:
    A rapid and simple co-precipitation method for iodine separation from natural samples was developed for determination of 129I using accelerator mass spectrometry (AMS). The method includes three steps, i.e. decomposition of organic iodine, iodine separation and target preparation using co-precipitation, and sensitive measurement of 129I/127I ratio using AMS. The recovery of iodine was higher than 90% for most natural water samples in the decomposition step using K2S2O8. Iodine in the digested sample was then co-precipitated as AgI-AgCl-Ag2SO3-Ag2SO4 with a typical recovery of 95-98%. It was observed that addition of 0.2 mg 127I carrier can significantly improve the measurement uncertainty of low-level 129I samples by enhancing iodine ion current. The overall recovery of iodine in the entire procedure was higher than 80%, and a detection limit of 1.0×105 atoms (or 2.2×10-17 g) for 129I was achieved. The developed method was validated by certified reference material (IAEA-418) and five types of natural water samples in comparison with results using the conventional solvent extraction method. Analytical results showed good agreement with the reference values for all samples, confirming the reliability of the developed method. The simple operation, with no need for organic solvent and small amount of iodine carrier addition make the developed method suitable for rapid and reliable determination of low level 129I in natural water samples.
    15  Rapid Elemental Determination and Discrimination of Coins Using Laser-induced Breakdown Spectroscopy
    Haochen Peng Yuzhu Liu Ying Chen Xu Lu Guoqing Chen Yu Chen
    2021, 42(4):203-209. DOI: 10.46770/AS.2021.128
    [Abstract](137) [HTML](0) [PDF 4.46 M](4451)
    Abstract:
    Damaged coins can be identified effectively via spectral analysis based on LIBS, which is of great significance for coin recycling. This paper takes the Renminbi (RMB), the Chinese currency, as the example, including the denominations of YI FEN, ER FEN, WU FEN, YI JIAO, WU JIAO and YI YUAN. Some characteristic lines of Mg, Al, Fe, Cr, Cu, Sn, Ni, Na and Ca were observed in the spectra, as well as the molecular bands of AlO. Principal component analysis (PCA) was used to reduce the dimension of the spectra of the different RMB coins. The samples after dimension reduction are classified by k-Nearest Neighbors (KNN), and 4 categories were obtained with a classification accuracy of 100%. Further, new spectra of different denomination RMB coins were added to the original data for the same analysis. The results are in good agreement which shows the potential of the combination of LIBS, PCA and KNN for the analysis and identification of different coins.
    16  New Possibilities for the Determination of Volatile Organic Compounds by Their Molecular Ions in Air Using Microsecond-Pulsed GD TOFMS
    Anna Gubal Victoria Chuchina Yegor Lyalkin Natalya Ivanenko Nikolay Solovyev Alexander Stroganov Alexander Ganeev
    2021, 42(3):120-127. DOI: 10.46770/AS.2021.031
    [Abstract](161) [HTML](0) [PDF 2.92 M](4440)
    Abstract:
    A recent trend in glow discharge analysis, previously considered as a ‘purely inorganic’ technique, is related to the effective ionisation of volatile organic compounds (VOCs). This approach was demonstrated to be capable of analysing VOCs in both model gas mixtures and ambient air. In the current study, the possibility of the direct determination of VOCs of different classes of organic compounds (including toluene, p-xylene, chlorobenzene and 1,2,4-trimethylbenzene) in ambient air using microsecond pulsed glow discharge time-of-flight mass spectrometry (μs-Pulsed GD TOFMS) with copper hollow cathode was demonstrated. The ionisation processes with the formation of molecular ions M+, which can be used for quantification, were discussed. The fragmentation of detected molecular ions of VOCs was found to be quite low, which benefits both qualitative and quantitative determination. The ease of identification and relative simplicity of the mass spectrum is promising for the analysis of VOC mixtures. One of the possible applications of the designed method is the direct determination of VOCs in human exhaled breath for the diagnosis of lung diseases, including lung cancer. However, revealing its potential applicability for this purpose requires further research.
    17  An Improved Method of Adhesion Force Measurement by Atomic Force Microscopy (AFM)
    Hong Jin Xiongyao Li Yuanyun Wen Hong Tang Xiaojia Zeng
    2022, 43(1):13-18. DOI: 10.46770/AS.2022.011
    [Abstract](195) [HTML](0) [PDF 8.62 M](4434)
    Abstract:
    The adhesion properties of lunar dust grains are a key to determine its motion state. Atomic force microscopy (AFM) is conducted to evaluate the adhesion properties of such ultrasmall grains. However, an efficient method to measure the adhesion properties of lunar grains has not yet been developed because of the difficulties in eliminating the effect of adsorption of water and gases on the grain surface. In this study, an improved method was proposed to measure the adhesion force of grains while effectively eliminating the gas molecule adsorption effect. In the proposed method, using a focused ion beam, a small grain was mounted onto the tip of an AFM probe then used to measure the adhesion force of the grain. To determine the effects of environmental pressure and temperature, the adhesion force between a silica ball and a silica wafer was measured under different conditions. Based on the results, the gas molecule adsorption effect can be effectively eliminated during adhesion force measurement through AFM at a temperature of 200 ℃ and an environmental pressure of <2.4 ×10?4 Pa, at which strong adhesion of the grain is achieved. The proposed method is suitable for the measurement of adhesion force in lunar grain samples.
    18  Determination of Trace Cd and Pb in Edible Salt and Soy Sauce by ETAAS Using Fluorescent Carbon Nanoparticles (FCNs) as Matrix Modifier
    Yunfang Wu Shusen Liu Yanwei Xu Lin Yu Zhe Yang Honghui Wang Yuansheng Guo
    2021, 42(3):160-165. DOI: 10.46770/AS.2020.196
    [Abstract](201) [HTML](0) [PDF 1.84 M](4429)
    Abstract:
    Lead (Pb) and cadmium (Cd) are non-essential but extremely noxious metallic elements, and the study of their impact on environmental pollution is of utmost importance. In this report, an economical and environmentally friendly matrix modifier, fluorescent carbon nanoparticles (FCNs), is utilized for the electrothermal atomic absorption spectrometry (ETAAS) determination of trace Pb and Cd in edible salt and soy sauce. FCNs have been characterized for use with UV-Vis spectroscopy, ?uorescence (FL), Fourier transform infrared spectrum (FT-IR) and transmission electronic microscopy (TEM). In comparison to traditional matrix modifiers, FCNs can effectively eliminate matrix interference. Using the proposed FCNs, the ETAAS method achieved a linearity of 10–50.0 μg L-1 for Pb and 0.4–4.0 μg L-1 for Cd; a limit of detection (LOD) for Pb in edible salt of 0.0140 mg kg-1 and in soy sauce of 0.0470 mg kg-1, and for Cd in edible salt of 0.0015 mg kg-1 and in soy sauce of 0.0005 mg kg-1. The method of additions chemical matrix modifier was used for Pb and Cd detection in this study. Excellent accuracy (93.0–101.0% recovery) and precision (0.19–0.85 %) of this procedure were obtained for soy sauce and edible salt. This work provides a new and economical strategy for the determination of trace Pb and Cd and is expected to facilitate future studies in the use of FCNs as a matrix modifier.
    19  Determination of Selenium by Platinum-coated Tungsten Coil Trap Hydride Generation-Atomic Absorption Spectrometry
    Dilek Yildiz
    2021, 42(4):197-202. DOI: 10.46770/AS.2021.026
    [Abstract](107) [HTML](0) [PDF 2.18 M](4291)
    Abstract:
    A highly sensitive analytical technique was developed in which gaseous hydrogen selenide generated by sodium tetrahydroborate reduction was transported and trapped on a resistively heated platinum-coated W-coil trap for in situ preconcentration. The selenium concentration was determined using hydride generation-atomic absorption spectrometry (HG-AAS). The surface of the W-coil was covered with platinum using the electrodeposition technique in the presence of H2 and Ar. According to the results of Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy (SEM-EDX) images, the ratio of Pt was 54.74% on the W-coil trap surface. Various experimental conditions, such NaBH4 and hydrochloric acid concentration, and carrier gas flow rate, were optimized. In addition, the effect of the hydride-forming elements was quantitatively evaluated. The limit of detection for Se was 21.1 ng/L. The proposed method was also applied to the determination of selenium in certified reference material (SRM 1640a Trace Elements in Natural Water) which showed that the analysis could be performed with a relative error of about 8%. The precision of the method was evaluated and a relative standard deviation (%RSD) lower than 10% was obtained.
    20  Depth Profile Analysis of Molybdenum Disulfide Film by Glow Discharge Mass Spectrometry
    Mengli Wang Bin Zhao Shangjun Zhuo Yueqin Zhu Lei Huang Rong Qian
    2021, 42(4):183-189. DOI: 10.46770/AS.2021.070
    [Abstract](172) [HTML](0) [PDF 1.64 M](4119)
    Abstract:
    In this work, the depth profile analysis capability with direct current glow discharge mass spectrometry (dc-GD-MS) was evaluated by examining molybdenum disulfide (MoS2) films on Al and steel substrates. The optimized glow discharge conditions for obtaining an ideal flat crater and an efficient signal intensity were a discharge current of 1.0–1.5 mA and a discharge pressure of 4.7 mPa. The dc-GD-MS depth profile analysis provided depth resolutions of 0.55 μm for the MoS2/Al sample and 0.70 μm for the MoS2/Steel sample. The interface of 4.46 μm for MoS2/Al and 4.55 μm for MoS2/Steel determined by dc-GD-MS was close to the thicknesses of 4.85 μm and 5.45 μm, respectively, as measured by field emission scanning electron microscopy (FE-SEM). A high-carbon steel standard sample (NIST SRM 1264a) was used to validate the reliability and accuracy of the method. Relative errors of less than 12% were obtained compared with the certified concentration and the relative standard deviation (RSD, n = 20) of typical elements within 10%. The dc-GD-MS depth profile analysis provided an efficient and reliable approach for the depth analysis of the MoS2 film.

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