Glow Discharge Mass Spectrometry Research Articles

Novel hollow-electrode glow discharge mass spectrometry for the quantitative analysis of protein content in food.

Protein content in food is an important indicator of nutritional value and food safety. Therefore, it is of great significance to accurately detect protein content in food. In this work, a combustion furnace and novel hollow-electrode glow discharge ion source-quadrupole mass spectrometry (HGD-MS) were designed, which were used to construct a "combustion furnace + mass spectrometry" experimental platform to detect the protein content in food. Five food standard samples were selected for the analysis. The food samples were combusted in the combustion furnace at a high temperature (1300 °C) in an oxygen-rich environment. The gas products were passed into the novel hollow electrode glow discharge ion source-quadrupole mass spectrometer. A standard curve of y = 635.06x + 11 082, R2 = 0.9994 was plotted by detecting the NO+ ion intensity at a relative standard deviation (RSD) of 1.8% to 5.7%. Using the same method, food samples no. 6 and 7 were combusted and NO+ ion intensity was measured to verify the accuracy of the quantitation curve. Subsequently, the protein content was determined using a nitrogen-to-protein conversion factor of 6.25. This method provides a rapid, accurate, and environmentally friendly approach for determining protein content in food.

Determination and study of correlations of relative sensitivity factors in metal and metal oxide samples by glow discharge mass spectrometry

The determination of relative sensitivity factor (RSF) plays a crucial role in achieving accurate quantitative analysis in glow discharge mass spectrometry (GD-MS). In this study, the RSF of typical elements in 14 metal and metal oxide matrices were determined, and their correlation with discharge parameters, matrix effects, the first ionization energies and sample shapes were investigated. It was found that discharge gas flow exerted a minor influence on RSF values in a nickel (Ni) metal sample, whereas discharge current significantly affected RSF, with variations up to 57.00 % for cobalt (59Co). The results revealed that matrix effects were more pronounced in metal oxides, with the relative standard deviation (RSD) of RSF for typical elements ranging from 25.17 % to 101.04 %. RSF values for the same element across different metal oxides showed a correlation with lattice binding energy (U0). Particularly, RSF values for 12 elements including 23Na, 27Al, 28Si, 45Sc, 52Cr, 56Fe, 59Co, 88Sr, 130Te, 138Ba, 139La and 140Ce within 7 metal oxides showed a significant correlation with U0 of the metal oxides. In terms of sample shape, pin samples generally yielded higher RSF values than flat samples in both metals and oxides. RSF accuracy was confirmed with standard samples of zirconium (Zr 73 MR10002 and Zr IARM 705–18) and iron oxides (Fe2O3-1 and Fe2O3-2) with relative errors within 17.50 % except for 12C. Subsequently, these RSF values were effectively utilized for the quantitative analysis of samples collected from the China Space Station (CSS). This comprehensive analysis elucidates the multifaceted influences on RSF values, enhancing the precision of trace element quantification in GD-MS.

Surface Fluorination of Nuclear Graphite Exposed to Molten 2LiF-BeF2 (FLiBe) Salt and Its Cover Gas at 700 °C.

This study demonstrates that the reaction of Li2BeF4 (FLiBe) with graphite both in the liquid phase and the gas phase of the molten salt leads to the formation of covalent and semi-ionic carbon-fluorine bonds at the graphite surface and is accompanied by surface microstructural changes, removal of C-O groups, and deposition of metallic beryllium, based on XPS, Raman, and glow discharge mass spectroscopy characterization. At 700 °C, the observed surface density of C-F is higher after 240 h than after 12 h of exposure to molten FLiBe salt; the kinetics of covalent C-F formation is slower than that of semi-ionic C-F formation, and the relative amount of semi-ionic C-F content increases with depth. The graphite sample exposed to the cover gas exhibits less surface fluorination than the salt-exposed sample, with predominantly semi-ionic C-F. Based on these observations and the observed LiF/BeF2 ratio by surface XPS, the hypotheses that fluorination of the salt-exposed graphite occurs via a gas-phase mechanism or that it requires salt intrusion are refuted; future studies are warranted on the transport of C-F semi-ionic and covalent species in graphite at high temperatures.

Analysis of Blackening Reaction of Zn–Mg–Al Alloy Coated Steel Prepared by Anodizing Process

The rising demand for black-treated steel faces challenges with conventional black painting due to issues like scratching and peeling, impacting corrosion resistance and aesthetics. This study explores an alternative method, anodic oxidation, to blacken the surfaces of galvanized or coated steel plates. Parameters like temperature, duration, current density, and gas type were varied during the blackening process. The investigation aimed to identify key factors influencing the blackening. Scanning electron microscopy observed the morphology, while energy-dispersive X-ray spectroscopy and glow discharge mass spectrometry analyzed the chemical composition distribution. X-ray diffraction and X-ray photoelectron spectroscopy conducted compound crystal structure analysis. Results indicate higher temperatures, longer durations, and higher current densities improve blackening through anodic oxidation. Increased magnesium proportion on the surface leads to roughness and porous magnesium oxide formation, enhancing light absorption and explaining the observed blackening effect.

Separation behavior of trace impurities during deep purification of zone-fused germanium tailings via vacuum distillation

Germanium is an important semiconductor material. With its wide application in high precision industries such as infrared optics, photovoltaics and semiconductor devices, the purity of elemental germanium has been put forward with higher requirements. This research focuses on the environmentally friendly vacuum distillation purification of zone-fused germanium tailings (99.98 %) to separate low-boiling-point trace impurities such as Zn, In, and Mg. These impurities hinder the preparation of ultrapure germanium (7 N). We propose a novel vacuum distillation–based deep purification process to effectively separate trace impurities in the zone-fused germanium tailings. The initial germanium and purified germanium are comprehensively analyzed using glow discharge mass spectrometry. Our vacuum purification results indicate that the impurity content is below 0.05 ppm for all elements except As. The As content reaches 0.87 ppm with a removal ratio of 96.1 %, resulting in elementary germanium with 99.9995 % purity. This method considerably increases the recovery ratio of germanium-rich secondary resources to over 95 % while efficiently eliminating low-boiling-point trace impurities such as Zn, Mg, and Pb from the zone-fused germanium tailings. The findings suggest the method’s substantial potential for industrial application. This study offers valuable insights into the deep purification and front-end preparation of high-purity germanium.

Impurities related micro-defects in GaSb crystal grown by LEC method

The epitaxial growth of devices based on gallium antimonide (GaSb) is negatively impacted by defects related to impurities in the crystal. Liquid encapsulated czochralski (LEC) technology was used to grow 2-inch Te-doped GaSb (100) single crystal ingots, which were then processed into polished wafers in order to investigate the origins and consequences of defects related to impurities. Polished GaSb wafers were found to have surface micro-defects. Energy dispersive x-ray spectroscopy (EDAX) and scanning electron microscopy (SEM) measurements indicate that the micro-defects are associated with carbon and oxygen impurities. Glow discharge mass spectrometry (GDMS) is used to identify the origins of carbon and oxygen impurities. Based on the findings, an optimization process was developed to enhance the crystal quality, and a micro-defect-free GaSb single crystal was produced.

Melt-grown semi-insulating Mn:β-Ga2O3 single crystals exhibiting unique visible absorptions and luminescence

Several acceptor dopants have been explored in β-Ga2O3 to produce semi-insulating substrates and epitaxial films. Fe and Mg make up the majority of research thus far; however, other transition metals provide potential alternatives for optimized performance. β-Ga2O3 bulk single crystals were grown by the Czochralski and vertical gradient freeze methods with a nominal dopant concentration of 0.25 at. % Mn. Ultraviolet-visible-near infrared spectroscopy and photoluminescence revealed polarization- and orientation-dependent optical absorptions (pleochroism) coupled with an orange luminescence. All samples were electrically insulating, on the order of 109–1011 ohm cm at room temperature, indicative of acceptor doping. Actual dopant concentrations of the intentionally doped transition metal and background impurities were determined via glow discharge mass spectrometry, indicating the macroscale segregation behavior. High-temperature resistivity measurements indicated an experimental acceptor level of 1.7 ± 0.2 eV. Hydrogenation of samples resulted in an increase in the orange luminescence and O–H stretching modes observable in the infrared spectrum. Density functional theory calculations were performed to determine the likely site-occupancy and acceptor level of Mn in the bandgap.

The Rapid Determination of Multiple Impurities in Ultra-pure LaNi5 Alloy by Glow Discharge Mass Spectrometry

The Rapid Determination of Multiple Impurities in Ultra-pure LaNi5 Alloy by Glow Discharge Mass Spectrometry

Optimizing the temperature gradient for CdZnTe crystal growth using the vertical Bridgman–Stockbarger method

CdZnTe (CZT) is considered an ideal material for the growth of HgCdTe (MCT) epitaxial layers and nuclear detection devices. The crystal quality of CZT is the key factor in the MCT-based infrared plane array and the performance of nuclear devices. Herein, we report the growth of CZT by optimizing the temperature gradient vertical Bridgman–Stockbarger method. The crystalline character of the obtained CZT has been examined using optical microscopy, IR transmission microscopy, high-resolution X-ray diffraction, X-ray tomography (XRT), Fourier-transform infrared spectroscopy and glow discharge mass spectrometry. The etch pit dislocation density of the CZT sliced wafers (111)-B was less than 4.0 × 103 cm−2, the triangular shape inclusions in the CZT volume of the double-grinding wafers have a sparse distribution, and the size can be controlled to be less than 5 μm, the typical full-width at half-maximum of the Bragg diffraction peak was 17.4″. The XRT image of polished CZT wafers (111)-B showed a uniform structure without strain and defects. About 100 % of the CZT wafers showed transmittance >50 % at 20 µm and the detected impurities in the crystal were low, Li 4.9 ppb and Na 2.9 ppb, indicating the formation of high-quality CZT crystals. This work provides a scheme to improve the crystal quality of CZT for high-performance device applications.

Surface modification of s235 steel, molybdenum, and tungsten using electron beam scanning and electric discharge machining

The process of surface modification of structural steel s235, molybdenum, and tungsten samples was carried out using two techniques—high-energy electron beam line scanning in a vacuum in a device used for electron beam welding and electric discharge machining (EDM), in which samples are submerged in the dielectric fluid. Elemental surface distributions were then examined using two spectrometric techniques: secondary ion mass spectrometry (SIMS) and glow discharge mass spectrometry (GDMS). Samples were also examined using scanning electron microscopy with energy dispersive x-ray analysis (EDX). SIMS, GDMS, and EDX data show the segregation of manganese out of the electron beam scan line at the surface of s235 steel. In the case of EDM machined s235 steel, no surface segregation of manganese is seen, while the line treated with this machining is enriched in hydrogen, carbon, and copper, as contaminants of the dielectric fluid (kerosene) and the copper electrode are used. The SIMS data for tungsten show that the electron beam cleans up the impurities, while the EDM technique adds them. The data for molybdenum show that the electron beam cleans the surface of hydrogen and iron while enriching it with sodium and potassium. EDM-treated molybdenum appears to be contaminated with carbon and potassium but detects lower levels of hydrogen, sodium, and copper than the untreated surface.

Depth-profiling analysis of ZnO layers with three morphologies by direct-current glow discharge mass spectrometry

In the fabrication of high-quality materials, information regarding the element concentration and distribution in the depth direction is particularly important. In this study, the potential applicability of direct-current glow discharge mass spectrometry (dc-GD-MS) was explored for depth-profiling analysis of zinc oxide (ZnO) layers on steel substrates. The ZnO layers on steel substrates presented three morphologies of thin films, network textures and nanorods fabricated by magnetron sputtering (ZnO-1/steel), sol–gel method (ZnO-2/steel) and hydrothermal synthesis (ZnO-3/steel), respectively. The discharge conditions were optimized based on dc-GD-MS to obtain the ideal depth resolutions. The results revealed that compared with ZnO layers of ZnO-2/steel and ZnO-3/steel, the dc-GD-MS depth-profiling analysis of ZnO-1/steel presented superior performance with depth resolution of 0.22 μm and a clear interface between ZnO layer and steel substrate. dc-GD-MS depth-profiling analysis suggested that the ZnO layer morphology, thickness and sputtering rate could affect the depth resolution. Furthermore, the fuzzy synthetic evaluation method (FSEM) suggested that the layer morphology had a greater impact on the depth resolutions than thickness and sputtering rate under the optimized discharge conditions. The study presented an efficient and sensitive approach for determining the elemental concentrations and distributions of semi-conducting materials, offering novel insights into material fabrication.

The effect of dopant concentration and annealing treatments on N-type Iodine doped CdTe

We report properties of highly conducting n-type cadmium telluride single crystals doped with iodine (CdTe:I). These crystals were grown with dopant concentrations in the range of 1017 cm−3 to 1019 cm−3 by Modified Vertical Bridgman (MVB) melt growth. Post-growth dopant activation, including Cd annealing, Te annealing, and rapid thermal annealing (RTA), was applied to improve free carrier density. The structural, optical, and electrical properties were analyzed by Glow Discharge Mass Spectroscopy (GDMS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Photoluminescence Spectroscopy (PL), optical absorption, Hall measurements, Capacitance-Voltage (CV) measurements, and time-resolved photoluminescence (TRPL). The results indicate that Cd annealing is the most effective activation method to get 100 % donor activation (n ≈ 2 ×1018 cm−3), which is close to the room temperature solubility limit of iodine. This leads to the lowest resistivity and the highest mobility. Moreover, this data suggests a potential role of Cd vacancy-related defects on electrical self-compensation.

Chemical Composition and Microstructure Characterization of High Purity CuMn Alloy for Integrated Circuit

High purity copper and copper alloy targets are the key supporting materials for the interconnection of integrated circuits in advanced processes. In this article, the chemical composition and microstructure of Cu-0.6wt%Mn alloy were characterized by means of Glow Discharge Mass Spectrometry, Inductive Coupled Plasma Emission Spectrometer, Optical Microscope and Scanning Electron Microscope. The results show that the total impurity content for Cu-0.69wt%Mn alloy is less than 1 ppm. The three key impurities contents of Ag and Fe and Si could meet the requirement of electronic materials for integrated circuits by use of high purity raw material and appropriate melting and casting methods. Mn content at different positions along the diameter direction fluctuates slightly between 0.66~0.72 wt%, and completely distributed uniformly in the Cu matrix without any trace of aggregation. Due to the influence of raw materials and casting technology, defects such as porosity and carbon inclusion are easy to appear in as-cast microstructure. Therefore, it is necessary to develop new casting mould and casting processing to improve the quality of ingots.

Studies of Dopamine Oxidation Process by Atmospheric Pressure Glow Discharge Mass Spectrometry.

An atmospheric pressure glow discharge ionisation source was constructed and utilized to study the dopamine (DA) oxidation process coupling with mass spectrometry. During the DA oxidation process catalysed by polyphenol oxidase (PPO), six cationic intermediates were directly detected by the atmospheric pressure glow discharge mass spectrometry (APGD-MS). Combined with tandem mass spectrometry, the structures of the dopamine o-semiquinone radical (DASQ) and leukodopaminochrome radical (LDAC●) intermediates and structures of the isomers of dopaminochrome (DAC) and 5,6-dihydroxyindole (DHI) were further characterised with the introduction of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and deuterium oxide (D2O) to APGD-MS. Meanwhile, UV-Vis studies confirmed the important role of PPO in catalyzing the DA oxidation reaction. Based on APGD-MS studies, a possible mechanism could be proposed for DA oxidation catalysed by PPO. Furthermore, APGD-MS could provide possibilities for the effective detection and characterisation of short-lived intermediates, even in complicated systems.

Molecular Ion Spectra in Glow Discharge Mass Spectrometry of Toxic and Physiologically Active Elements in Hydroxyapatite

Molecular Ion Spectra in Glow Discharge Mass Spectrometry of Toxic and Physiologically Active Elements in Hydroxyapatite

Preparation of High-Purity Magnesium from Electrolytically Produced Crude Magnesium via Vacuum Distillation

Metallic Mg is an important strategic metal and its properties are greatly affected by impurities. Silicothermic reduction and electrolysis are the most used approaches to prepare metallic Mg. The products of these processes need to be further refined to obtain high-purity Mg metal. However, previous research has mainly focused on refining the crude Mg (CM) produced via silicothermic reduction, whereas no in-depth investigations have been conducted on refining the CM produced via electrolysis. Here, vacuum distillation was used to refine electrolytically produced CM. The content and morphological characteristics of the impurity elements in CM were studied via glow discharge mass spectrometry, mineral dissociation analysis, and electron probe microanalysis. The effect of different distillation temperatures and times on the quality of the refined Mg was investigated. The results show that the main impurity elements are Al, Fe, Si, Ti, Cr, S, Cl, and Ni. The content of impurities, such as Si, Al, Fe, Ni, Ti, and Cr, in the refined Mg is significantly reduced at a temperature of 1023 K and a time of 120 min, and the purity of the refined Mg reaches 99.99%, which meets the Mg9999 national standard for primary Mg ingots in China (GB/3499-2011).

On the way to SI traceable primary transfer standards for amount of substance measurements in inorganic chemical analysis

During its 25 years of existence, the Inorganic Analysis Working Group of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM IAWG) has achieved much in establishing comparability of measurement results. Impressive work has been done on comparison exercises related to real-world problems in fields such as ecology, food, or health. In more recent attempts, measurements and comparisons were focused on calibration solutions which are the basis of most inorganic chemical measurements. This contribution deals with the question of how to achieve full and transparent SI traceability for the values carried by such solutions. Within this framework, the use of classical primary methods (CPMs) is compared to the use of a primary difference method (PDM). PDM is a method with a dual character, namely a metrological method with a primary character, based on the bundling of many measurement methods for individual impurities, which lead to materials with certified content of the main component. As in classical methods, where small corrections for interferences are accepted, in PDM, many small corrections are bundled. In contrast to classical methods, the PDM is universally applicable to all elements in principle. Both approaches can be used to certify the purity (expressed as mass fraction of the main element) of a high-purity material. This is where the metrological need of National Metrology Institutes (NMIs) for analytical methods meet the challenges of analytical methods. In terms of methods, glow discharge mass spectrometry (GMDS) with sufficient uncertainties for sufficiently small impurity contents is particularly noteworthy for the certification of primary transfer standards (PTS), and isotope dilution mass spectrometry (IDMS), which particularly benefits from PTS (back-spikes) with small uncertainties, is particularly noteworthy for the application. The corresponding relative uncertainty which can be achieved using the PDM is very low (< 10−4). Acting as PTS, they represent the link between the material aspect of the primary calibration solutions and the immaterial world of the International System of Units (SI). The underlying concepts are discussed, the current status of implementation is summarised, and a roadmap of the necessary future activities in inorganic analytical chemistry is sketched. It has to be noted that smaller measurement uncertainties of the purity of high-purity materials not only have a positive effect on chemical measurements, but also trigger new developments and findings in other disciplines such as thermometry or materials science.Graphical Primary Transfer Standards (PTSs) are the link between the immaterial world of the International System of Units (SI) and the material aspects of the primary calibration solutions.

Effects of reduction temperature and diluent content on the properties of high-purity tantalum powder prepared using the Hunter process

The Hunter process is predominantly used to manufacture high-purity Ta powder. Among the various physical properties of the Ta powder, its impurity content is particularly crucial. In this study, the process temperature at which a liquid pool of raw material and diluent can be formed and the corresponding amount of diluent were analyzed by performing thermodynamic simulations using FactSage and HSC Chemistry software. Based on the results of the thermodynamic simulations, Ta powder was prepared at process temperatures of 700–800 °C and a specific amount of NaCl at each temperature. Thereafter, the prepared Ta powder was recovered and a post-treatment process was performed to ensure purity. The characteristics of the recovered Ta powder were evaluated according to each process condition by oxygen/nitrogen/hydrogen analysis, scanning electron microscopy/energy-dispersive X-ray spectroscopy, glow discharge-mass spectrometry, and X-ray diffractometry. The synthesized Ta powders were confirmed to exhibit purities >99.95% and oxygen, nitrogen, and hydrogen concentrations of 447, 21, and 10 ppm, respectively. The characterization results indicated that the produced Ta powders were fabricated entirely in a single phase with high purity and recovery rates. Finally, process optimization was achieved for manufacturing high-purity (≥3 N5) Ta powder with controllable impurities.

Time-of-flight mass spectrometry with pulsed glow discharge for direct determination of volatile organic compounds in air, nitrogen and argon. Volatile organic compounds ionization processes

Determination of volatile organic compounds (VOCs) in various gases, including atmospheric and exhaled human air, is required to solve a wide range of environmental problems, control the composition of various gases and is increasingly used for diagnosis of various diseases. Lately, methods of soft ionization with minimal fragmentation of the components have been rapidly developed. In particular, our research group is developing an approach to direct analysis of mixtures of VOCs using time-of-flight pulsed glow discharge mass spectrometry. Previously, the effects of different gases and gas mixtures on ionization processes were not compared. Therefore, the ionization mechanisms of VOCs in argon, nitrogen, and air were investigated in the present work. Toluene, p-xylene, chlorobenzene and 1,2,4-trimethylbenzene were chosen as the model VOCs. Optimization of microsecond pulsed glow discharge parameters (period and duration of the discharge pulse, repelling pulse delay time and pressure in the discharge cell) for each compound and a gas mixture of several VOCs was carried out. The predominant ionization mechanisms are the formation of a VOC molecular ion by Penning ionization and the proton transfer reaction; their influence being different for various gases. It is shown that the use of argon even with a small addition of water leads to the predominance of the proton transfer reaction, whereas in nitrogen and air the Penning ionization predominates. The maximum VOC intensities were achieved in air, and the developed approach

Screening of hepatocellular carcinoma via machine learning based on atmospheric pressure glow discharge mass spectrometry.

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors with a high mortality rate. The diagnosis of HCC is currently based on alpha-fetoprotein detection, imaging examinations, and liver biopsy, which are expensive or invasive. Here, we developed a cost-effective, time-saving, and painless method for the screening of HCC via machine learning based on atmospheric pressure glow discharge mass spectrometry (APGD-MS). Ninety urine samples from HCC patients and healthy control (HC) participants were analyzed. The relative quantification data were utilized to train machine learning models. Neural network was chosen as the best classifier with a classification accuracy of 94%. Besides, the levels of eleven urinary carbonyl metabolites were found to be significantly different between HCC and HC, including glycolic acid, pyroglutamic acid, acetic acid, etc. The possible reasons for the regulation were tentatively proposed. This method realizes the screening of HCC via potential urine metabolic biomarkers based on APGD-MS, bringing a hopeful point-of-care diagnosis of HCC in a patient-friendly manner.