Main Impurities Research Articles

Refining light impurity content estimates at the lower divertor based on experimental data in WEST

WEST is an actively cooled, long-pulse tokamak with nearly all plasma-facing components (PFC) made of tungsten (W). One of the aims of WEST is to study plasma operation with W PFCs in preparation for long-pulse operation on W divertor devices like ITER (Bucalossi et al., 2014) [1]. For long-pulse operation, the W impurity content and transport to the core plasma are critical concerns that require further measurement and interpretation in order to improve plasma performance and PFC durability. In low confinement mode (L-mode) operation, the sputtering of tungsten is not expected to be driven by the plasma itself (D), but by the main light impurities (C, B, O, N) observed at trace levels in WEST. Identifying the main W sources and understanding W transport in the SOL are key metrics for plasma performance, which are simulated with Scrape-Off Layer (SOL) impurity transport codes (SOLEDGE-ERO, OEDGE-DIVIMP). Previous studies have used O as proxy for light impurity with a global content varying from 3 to 5% in SOL transport simulations (Genova et al., 2021; Rooij et al., 2020; Klepper et al., 2022) [2–4]. A power scan was performed in a standard WEST magnetic equilibrium with LH injected power up to 5 MW. Density and temperature were measured with flush-mounted Langmuir probes (Dejarnac et al., 2021) [5]. The impurity fluxes are estimated by applying the number of ionizations per photons (S/XB) coefficients calculated with the collisional-radiative model “ColRadPy” (Johnson et al., 2019) [6] to the spectral radiance measured with the WEST visible spectroscopy system (Meyer et al., 2016) [7]. This work details how the low-Z impurity content (C, O) near the divertor target was refined using the visible spectroscopy for several impurity charge states, coupled with ColRadPy to infer the content of all impurity charge states at the divertor. First results shows that the main light impurity is C and not O as originally assumed. This inferred impurity content is then used to evaluate the W sputtering at the divertor, considering the sheath at the divertor. A quantitative comparison is performed with the W flux at the divertor measured with visible spectroscopy that shows a qualitative agreement, but not fully consistent at the strike point position. This, in turn, suggests that the impurity content is not complete with O and C only.

Pottery of the Kalinkino Culture from the Barsov Gorodok III/2 Settlement: Technical and Technological Characteristics

Purpose. Barsova Gora is a unique archaeological and landscape site located in the Tyumen Region (West Siberia) of the Russian Federation. The technical and technological analysis of Kalinkino ceramics from the Barsov gorodok III/2 settlement (25 vessels) was performed in accordance with the method developed by A. A. Bobrinsky.Results. For the manufacture of vessels at the Barsov gorodok III/2 settlement, ferruginous clays were selected. Five subspecies of clay have been identified, differing in the sandiness degree and natural impurities composition. The most common subspecies of clay is weakly sandy clay with natural inclusions of brown ironstone. Three recipes for molding compond were defined: 1) clay + chamotte (21 vessels); 2) clay + chamotte + sand (3 vessels); 3) clay + sand (1 vessel). Vessels were made using patchwork molding, presumably on a base mold. Surfaces of vessels were processed by mechanical smoothing and glossing. There are 10 variants of combining different tools. The most common variant is smoothing vessel both surfaces using a serrated tool. Firing of pottery could take place in reducing or semireducing gas environment.Conclusion. A comparison of pottery traditions of the Kalinkino culture from the Barsov gorodok III/2 settlement and the Barsova Gora III/20 settlement revealed their similarity. It is manifested in the selection of weakly sandy ferruginous clays for vessels production. The dominant recipe for molding compound on both sites is clay + chamotte. Vessels were made using patchwork overlay. There are differences in the range of artificial additives used in the ceramic production, recipes for molding compound, surface treatment options. Pottery of the Kalinkino culture from the Barsov Gorodok III/2 settlement demonstrates similarity with the Barsovo culture products. The similarity is manifested in the use of weakly sanded ferruginous clays and the use of chamotte as the main mineral impurity. It also converges with the pottery of the Surgut variant of the Kulay cultural-historical community due to use of chamotte and patchwork overlay. However, there are significant differences between ceramics of the Surgut variant of the Kulay cultural-historical community and the Kalinkino culture from the Barsov gorodok III/2 settlement manifested: it lies in the use of shadings and flap veneer in the Kulay pottery.

Study on Mechanism of Titanium Slag Smelting in DC electric Arc Furnace

Based on the production practice of a 30MWA large DC electric furnace in Yunnan, this paper discusses the basic reactions in smelting titanium slag, and discusses the thermodynamic and kinetic behaviors of the main elements and impurities. The results show that the reduction reaction in the smelting process is carried out simultaneously in the multi-component system of Al2O3-CaO-MgO-SiO2-TiO2. The titanium slag containing more than 80% TiO2 can be obtained by enrichment smelting of ilmenite in a large high-power enclosed direct current electric arc furnace, and the output includes by-product pig iron. Impurities MgO, CaO and Al2O3 in titanium concentrate will not be reduced during reduction smelting; SiO2, MnO and V2O5 will be reduced in varying degrees, and the reduced products Si, Mn and V will dissolve in the metal Fe phase or be enriched in titanium slag.

Structural identification and comprehensive comparison of saponin-related impurities present in the three different compound glycyrrhizin tablets

Compound Glycyrrhizin Tablet (CGT) is a glycyrrhizin-containing (monoammonium glycyrrhizate, MAG) preparation, which has been widely used in clinical treatment of chronic liver diseases, eczema, atopic dermatitis and other conditions. However, the impurity profile of CGT has not yet been completely elucidated. In this study, eight main saponin-related impurity compounds were initially isolated and identified. Thereafter, based on the characteristic MS/MS fragmentation pathways analysis of the isolated compounds, a novel strategy for characterization and identification of saponin-related impurities was proposed. Then, a total of 41 saponin-related impurities were identified or tentatively characterized in CGTs. Furthermore, principal component analysis (PCA), Wayne diagram and heatmap analysis revealed that the process-related impurity profile in CGTs from three different manufacturers was significantly different. Overall, our findings provided additional technological support for evaluating saponin-related impurities, thereby laying a solid foundation to develop strategies for future product quality improvement.

Homoepitaxy Growth of High‐Quality AlN Film on MOCVD AlN Template by Hydride Vapor Phase Epitaxy

Herein, AlN film grown on metal‐organic chemical vapor deposition (MOCVD) AlN template by high‐temperature hydride vapor phase epitaxy (HVPE) is characterized. High‐resolution X‐ray diffraction results show that the crystal quality of the film is improved compared with that of the template. Atomic force microscopy shows that the root mean square roughness value also decreases. Cathodoluminescence spectra show that the main impurities in the epitaxial layer and template are oxygen atoms. Raman spectroscopy and geometric phase analysis show that HVPE AlN samples maintain a compressive stress internally, which is the key to inhibit film cracking. Transmission electron microscope characterization reveals that most of the dislocations at the interface inherit from MOCVD AlN template, incline in the subsequent growth, react with each other, and finally annihilate. The dislocation bending and reduction mechanism are demonstrated.

The Effect of Iron- and Calcium-Rich Waste Rock’s Acid Baking Conditions on the Rare-Earth Extraction

The work investigates the effect of sulfuric acid baking on rare earth element (REE) extraction from two waste rock samples from a phosphate mine. The role of different mineralogical assemblages and the degree of alteration (i.e., weathering), and the behavior of the main impurities–iron, phosphorus, and calcium–on REE extraction are emphasized. For both samples, the sulfuric acid baking at 25 °C, during 15 min, H2SO4:sample (w/w) mass ratio of 0.45:1 is the best condition for achieving the selective leaching of REE. For the iron rich-sample, the increase in temperature reduces REE extraction and increases iron dissolution. The corresponding sulfuric acid consumed by goethite (α-FeOOH) from 25 °C to 160 °C acid baking is ten times higher than that required for the monazite (REEPO4) reaction. Conversely, higher REE and lower iron extraction are observed by increasing (sulfuric acid/sample) mass ratio (0.95:1). Due to the high sulfuric concentration during dissolution, a local saturation zone close to the dissolution front caused the precipitation of iron oxyhydroxides. The calcium-rich sample shows lower REE extraction by leaching (63% maximum) mainly due to the entrapment of REE-bearing minerals by a gypsum layer, and lanthanide’s uptake by calcium sulfate compounds formed during leaching. The results were discussed with the help of a detailed characterization of the residues.

Identification of undescribed key impurities of homoharringtonine bulk drug

The knowledge of impurities is an important issue and the base of quality control in modern drugs. To date, the quality control of the antitumor drug homoharringtonine (HHT) is still not sufficiently solved and needs to be improved. Six main impurities, drupacine, cephalotaxine, desmethylcephalotaxinone, harringtonine, 3-O-acetyl-cephalotaxine and 2'R,3'S-isoharringtonine were traced during HHT drug production by HPLC and LC-MS analyses. Additionally, we were able to isolate and identify three undescribed key trace impurities, neohomoharringtonines A–C. Their structures were established by 1D-, and 2D NMR experiments combined with mass spectrometry. An improved quality inspection ability of HHT was constructed.

Atomic layer deposition of CoF2, NiF2 and HoF3 thin films.

The present study describes atomic layer deposition (ALD) processes and characterization of CoF2, NiF2, and HoF3 thin films. For CoF2 deposition CoCl2(TMEDA) (TMEDA = N,N,N',N'-tetramethylethylenediamine) and NH4F were used as precursors. CoF2 deposition was studied at 180-275 °C, resulting in a growth per cycle (GPC) of 0.7 to 1.2 Å. All the films consist of tetragonal CoF2 according to XRD. The impurity contents were measured with ToF-ERDA and less than 1 at% of N and Cl were detected in the films, indicating effective reactions. In addition, the F/Co ratio is close to 2 as measured by the same method. The saturation of the GPC with respect to precursor pulses and purges was verified at 250 °C. The common feature of ALD metal fluoride films - remarkable roughness - is encountered also in this process. However, the films became smoother as the deposition temperature was increased. CoF2 deposition was also demonstrated on graphite substrates. NiF2 deposition was studied at 210-250 °C by using Ni(thd)2 and TaF5 or a new fluoride source NbF5 as the precursors. Tetragonal NiF2 was obtained, but the oxygen and hydrogen contents in the films were remarkable, up to ∼11 at%, as measured by ToF-ERDA. This was observed also when the films were in situ capped with YF3. NbF5 was shown to be a potential fluoride precursor by combining it with Ho(thd)3 to deposit HoF3 films. Orthorhombic HoF3 was obtained at deposition temperatures of 200-275 °C. The films deposited at 235-275 °C are pure, and the Nb contents in films deposited at 250 and 275 °C are only 0.21 and 0.15 at%. The main impurity in both films is oxygen, but the contents are only 1.5 and 1.6 at%. The saturation of the GPC with respect to precursor pulses was verified at 250 °C. The GPC is ∼1 Å.

Preparation of anhydrous aluminum fluoride

Because direct roasting of aluminum fluoride hydrate will hydrolysis, resulting in higher alumina content in aluminum fluoride products. To solve this problem, a two-step process for the preparation of anhydrous AlF3 from AlF3·3H2O and NH4HF is described in this paper. First, AlF3·3H2O was dried at 220 ℃ for 9–12 h, and then NH4HF (the mass ratio of AlF3·3H2O to NH4HF was 1:20) was added, and the mixture was roasted from room temperature to 650 ℃. The results showed that the hydrolysis of aluminum fluoride can be avoided effectively by the two-step roasting method with NH4HF, the purity of the anhydrous AlF3 was 99.8 wt%, and the concentration of alumina, the main impurity, was less than 0.1 wt%.

Analysis of terbinafine in PLGA-based drug delivery systems by a fast and sensitive UHPLC-DAD method.

A novel ultra-high performance chromatography method with multichannel detection that allows fast, sensitive, and robust analysis of an antifungal drug terbinafine and its three main impurities β-terbinafine, (Z)-terbinafine, and 4-methylterbinafine in just 5.0 min has been developed. Analysis of terbinafine is important in pharmaceutical analysis since it enables the detection of its impurities at very low concentrations. In this study, we focused on the development, optimization, and validation of the UHPLC method as well as its subsequent application in the evaluation of terbinafine and its three main impurities in the dissolution medium to reveal the incorporation of terbinafine in two poly(lactic-co-glycolic acid) (PLGA) carriers and testing of the drug release at pH 5.5. PLGA based drug delivery systems such as solid dispersions, thin films, microparticles, and nanoparticles are new favorable ways of terbinafine administration. PLGA features excellent tissue compatibility, biodegradation, and adjustable drug release profile. Our pre-formulation study indicates that poly(acrylic acid) branched PLGA polyester has more suitable properties than tripentaerythritol branched PLGA polyester. Therefore, the former is likely to enable design of a new drug delivery system for topically applied terbinafine that could facilitate its administration and increase patient compliance.

Validation of method for analysis of glucose in food additives

The dangers of consuming various food and drink products containing substances with a potential risk to human health are the subject of increased interest. There is a drive among manufacturers and the scientific community to ensure safety in the use of various foods and beverages with proven and/or suspected links to one or another disease state. Fast and reliable methods of analysis are increasingly sought for the purpose of establishing the type and concentrations of the contained substances and elements, which methods support the implementation of strict control of the quantitatively regulated levels of various indicators, including main components and impurities. The current work presents a validation procedure of an iodometric method for determining the content of glucose as the main component of three types of nutritional supplements. To evaluate the method, results for the analytical characteristics specificity, repeatability, accuracy and linearity are presented and analyzed.

Characterization of Street Drugs Using Handheld Fourier Transform Raman Spectroscopy

Handheld Raman spectroscopy offers a rapid and mobile technique for determining drugs nondestructively. The technique offers further advantage for analyzing drug products (DPs) thanks to its ability to measure samples through packaging, thus preserving evidence integrity and continuity. This research evaluated the use of handheld Fourier transform (FT)-Raman spectroscopy for characterization of street DPs (n = 254) of diverse formulations. Raman spectra of DPs inside their packaging were collected and matched against the instrumental in-built library, and then exported to Matlab 2020a for offline spectral interpretation. Reference analysis was confirmed using gas chromatography–mass spectrometry (GC–MS) and infrared (IR) spectroscopy. The main drugs present were 1,3-trifluoro- methylphenylpiperazine, cocaine, ketamine, 3,4-methylenedioxymethamfetamine, mephedrone, and 1-benzylpiprerazine. The main impurities present in DPs were benzocaine, caffeine, and lactose. The impurities affected the Raman signature (enhanced or inhibited) of DPs, enabling profiling of DPs and visualizing patterns among different products. These latter patterns were featured in the similarities highlighted by the correlation coefficient values between different DPs, and by adjacent clusters of different DPs envisaged in the principal component analysis scores plot.

GEOCHEMICAL CHARACTERISTICS OF THE SALTYCHIAN GRANITES (WESTERN AZOV AREA) ACCORDING TO THE ICP-MS RESEARCH RESULTS

GEOCHEMICAL CHARACTERISTICS OF THE SALTYCHIAN GRANITES (WESTERN AZOV AREA) ACCORDING TO THE ICP-MS RESEARCH RESULTS

Recycling of diamond-wire sawing silicon powder by direct current assisted directional solidification

As the unavoidable by-products in the production of solar cells, the recycling and reuse of diamond-wire sawing silicon powder (DWSSP) have always been a key issue in the solar energy industry. However, until now, there is no effective method to achieve effective recovery of high-purity silicon. In this work, a new method was proposed to achieve the recycling of DWSSP. Direct current, as an external means, was introduced into the recycling process of DWSSP, and its influence mechanism on impurity removal process was also discussed. By optimizing the local temperature gradient at the front of the Solid-Liquid interface, and the impurity diffusion behavior at the front of the interface was improved. After purification, the impurity content in the silicon ingot is reduced significantly. Among them, Al, as the main metal impurity element was reduced to less than 5ppmw (from 13580ppmw), and Ni (80.78ppmw), Fe (57.60ppmw), Ti (5.79ppmw), etc. decreased to less than 1ppmw. This work improved the purification efficiency of DWSSP, and put forward an optimized recycling method, which is expected to realize the direct reuse of DWSSP in the photovoltaic industry.

Development and optimization of stability-indicating method of ethinylestradiol, levonorgestrel, and their main impurities using quality by design approach

The association of Ethinylestradiol 0.03 mg and Levonorgestrel 0.15 mg is a hormonal contraceptive that combines estrogen and progestogen. According to a bibliographic survey, these combined drugs present at least 18 known degradation products, which are required to control the potential impurities harmful to human health. The high number of impurities and the low concentrations of the active pharmaceutical ingredients (APIs) and their respective degradation products increase the complexity of the stability-indicating method development for this medicine. Thus, this work aimed to develop and optimize the stability-indicating method using the quality by design (QbD) approach and in-silico tools for application in samples of oral contraceptives sold in Brazil. The analysis samples were initially subjected to a forced degradation study through 7 days of exposure under acid and alkali hydrolysis, oxidative condition, and oxidation by metal ions. In addition to the chemical exposure, the sample was subjected to physical stress through 10 days of exposure under dry heat, moisture, and photolytic degradation. These exposure samples were analyzed in the development and optimization of chromatographic conditions. As a result, the developed method was able to separate 20 known substances, including the two APIs and their respective 18 degradation products, as well as unknown degradation products obtained by the forced degradation study. Finally, this stability-indicating method was successfully applied for comparative analysis of contraceptive drugs marketed in Brazil, newly purchased and subjected to accelerated stability condition at 40 °C and 75% RH over the 6-month period.

Extraction and Recovery of Metals from Spent HDS Catalysts: Lab- and Pilot-Scale Results of the Overall Process

The present study proposes an overall recycling process for spent hydrodesulfurization (HDS) catalysts. The process put together stages already known in the technical literature, tested again with samples coming from the roasting stage in a pilot kiln, which is the most limiting stage of metal recovery from spent catalysts. These catalysts contain valuable metals like cobalt (Co), molybdenum (Mo), nickel (Ni), and vanadium (V). In particular, one Co-Mo catalyst was treated in order to optimize the roasting step (time, soda ash, and temperature) at a pilot scale and thus maximize the extraction yield of molybdenum (Mo) and vanadium (V). In particular, a dry Co-Mo catalyst was used. After roasting at 700 °C for 2.5 h, the best conditions, the catalysts underwent water leaching, separating Mo and V from Co and the alumina carrier, which remained in the solid residue. The pregnant solution was treated to remove arsenic (As) and phosphorus (P), representing the main impurities for producing steel alloys. V was precipitated as NH4Cl, and further calcined to obtain commercial-grade V2O5, whereas Mo was recovered as molybdic acid by further precipitation at a pH of around one. Thus, molybdic acid was calcined and converted into commercial-grade MoO3 by calcination. The hydrometallurgical section was tested on a lab scale. The total recovery yield was nearly 61% for Mo and 68% for V, respectively, compared with their initial concentration in the spent Co-Mo catalysts.

Establishment of SI-traceable purity assessment of Fumonisin B1 using a combination of quantitative 1H NMR and mass balance

The accurate purity assessment of Fumonisin B1 (FB1) is of great challenge due to the lack of inherent chromophore, which is important for the development of FB1 certified reference material. In this study, differential scanning calorimetry (DSC), mass balance and quantitative 1H nuclear magnetic resonance (qH NMR) methods were developed and validated for international system of unit (SI) traceable purity assessment of in-house prepared FB1. The thermodynamic analysis showed no typical melting peak was observed for FB1, indicating DSC was not applicable for purity assessment of FB1. A high-performance liquid chromatography coupled with corona charged aerosol detector (HPLC-CAD) method was developed and an isocratic elution procedure was optimized for the chromatographic purity analysis of FB1. The linear range of optimized HPLC-CAD method could not cover the concentration range of FB1 and the structure-related impurity in the raw material, which was identified to be partial hydrolyzed FB1 (pHFB1). The correction factor used to correct the chromatographic purity obtained by area normalization method was approximately 0.2 %. Moisture (0.30 %) and pHFB1 (0.48 %) were the main impurities according to the mass balance analysis. A mixture of dimethyl sulfoxide-d6 and trifluoroacetic acid-d was confirmed to be a suitable deuterated solvent for accurate qH NMR analysis of FB1. The purity obtained by mass balance (99.13 % with uncertainty of 0.06 %) and qH NMR (99.12 % with uncertainty of 0.28 %) showed good consistency and equivalent precision. These methods are expected to be applicable to development of FB1 certified reference material with metrological traceability to the SI unit to ensure comparable and reliable detection results.

A novel low‐energy approach to leucoxene concentrate desiliconization by ammonium bifluoride solutions

AbstractBACKGROUNDDespite the large reserves of titanium ores, their treatment by basic approaches to obtain titanium products is not always economically feasible due to various factors. One of these problems is the high content of silicon in the ores.RESULTSThe paper considers the desiliconization of a leucoxene concentrate with an aqueous solution of ammonium bifluoride. It was found that at 80 °C the main impurities, such as silicon and iron, pass into solution in the form of corresponding ammonium–fluorine complex compounds.CONCLUSIONSThe degree of desiliconization was up to 99%. Aluminium reacts with ammonium bifluoride, but is almost not leached into solution due to its low solubility. Titanium does not react due to its relatively higher reaction Gibbs energy among other metals in reaction with ammonium bifluoride. The content of titanium oxide in the calcined leaching residue was 85.52 wt%. The resulting residue corresponds to the raw material used in industry for the production of titanium dioxide pigment or titanium metal by the chlorine method. Iron and silicon can be precipitated from the leaching solution. Furthermore, the resulting filtrate can be evaporated in order to regenerate and reuse ammonium bifluoride. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Indirect GC‐MS Method via Alcoholysis Reaction for Rapid Detection of Organoaluminum Compounds and its Impurities: A Case Study of Triethylaluminium

AbstractOrganoaluminum compounds have been employed as catalysts in many reactions. However, due to their high reactivity of the Al−C bond towards water or air, the accurate analysis and detection of organoaluminum compounds are still challenging. Here we demonstrate the possibility of rapidly and precisely detecting the purity and impurities of triethylaluminium (TEAL). An indirect GC‐MS method via alcoholysis reaction using a designed alcoholysis reactor was adopted to detect and separate the main components and impurities of the synthesized TEAL. Previously, the nuclear magnetic resonance (NMR) and the inductively coupled plasma‐mass spectrometer (ICP‐MS) methods were also selected to detect the main compounds in the synthesized TEAL. The impurities in TEAL was identified as n‐butyl aluminum, and the purity of synthesized TEAL is 97.47 % with high accuracy (ca. 99 %). This work suggests a new strategy to detect the purity and impurities of some kind of hazardous compounds.

Experimental and Theoretical Study of Ultra-Hard AlMgB14-TiB2 Composites: Structure, Hardness and Self-Lubricity

It is known that the presence of oxygen phases in hard materials leads to an undesirable decrease in the mechanical properties. In materials based on AlMgB14, the main oxygen impurity is spinel MgAl2O4; it significantly reduces the hardness of AlMgB14 and its formation during sintering is inevitable. In this work, the ultra-hard spark plasma sintered (SPSed) AlMgB14-TiB2 composite material was fabricated from the AlMgB14-TiB2 precursor obtained by self-propagating high-temperature synthesis (SHS). Due to the high synthesis temperatures, the main oxygen phase in the obtained composite was Al4B2O9 instead of spinel MgAl2O4. It was found that the obtained composite has excellent mechanical properties. The maximum hardness of the sample is 44.1 GPa. The presence of oxygen in the form of the Al4B2O9 phase led to unexpected results: the friction coefficient of the obtained AlMgB14-TiB2 composite under dry conditions against the Al2O3 counter-specimen is approximately four times lower than the friction coefficient of pure ceramic AlMgB14 (0.18 against 0.7, respectively). Based on the observed results, it was found that the Al4B2O9 particles formed during the SHS are responsible for the low friction coefficient. The quantum chemical calculations showed that the elastic moduli of Al4B2O9 are significantly smaller than the elastic moduli of AlMgB14 and TiB2. Thus, during sliding, Al4B2O9 particles are squeezed out onto the composite surface, form the lubricating layer and reduce the friction coefficient.