Tungsten Concentration Research Articles

Development of an Inductively Coupled Plasma Mass Spectrometry Method for Quantification of Extracted Tungsten from Glass Prefilled Syringes Used as a Primary Packaging for Pharmaceutical and Therapeutic Protein Products

Leachable tungsten is associated with protein aggregation and precipitation in glass prefilled syringes, and this may trigger immunogenicity concerns. Determining the level of leachable tungsten from glass prefilled syringes is critical for assuring quality of certain biopharmaceutical drug products. An inductively coupled plasma mass spectrometry (ICP/MS) quantification method was developed to determine elemental tungsten in syringe extracts. The syringe was extracted using 0.5% ammonium hydroxide (pH 11), heat (75 °C), and sonication. The resulting extraction solution was diluted 10 fold prior to ICP/MS analysis. Syringes from three syringe lots containing known low (average 28.0 ng), medium (average 189.4 ng), and high (average 631.9 ng) levels of tungsten were extracted three times each. All syringes with total tungsten greater than 14 ng had extraction efficiency greater than 90% with the first two extractions combined. The calibration curve range was 0.1-200 μg/L tungsten with iridium as the internal standard, and the correlation coefficient was ≥1.0000. The limit of detection at 0.05 μg/L tungsten and limit of quantification at 0.1 μg/L tungsten were determined as having a signal-to-noise ratio greater than 40 and 80 times compared with the blank, respectively. The ICP/MS method was selective for tungsten and iridium in the presence of other metals. Accuracies of spiked tungsten, at three different levels, in syringe extracts were >99% with precision relative standard deviation (RSD) (n = 5) of ≤1%. The matrix effect of the syringe extract media and carryover of tungsten and internal standard were negligible. Onboard stability of the syringe extracts over three days had a tungsten concentration RSD (n = 3) of ≤1%. Syringe extractions performed with 0.45-0.55% ammonium hydroxide had spike recoveries ≥99% and demonstrated extraction solution robustness. Quantified residual tungsten in syringes extract by ammonium hydroxide and analyzed by ICP/MS was acceptable based on extraction efficiency and method performance. Elemental tungsten is a known leachable from glass prefilled syringe used as a ready-to-inject drug device in the pharmaceutical industry. Tungsten is a residual artifact from the manufacturing process of the syringe. The leachable tungsten level is of a concern, as it can affect the quality of the filled drug product. To understand possible leachable quantity of tungsten from the prefilled syringe, a tungsten extraction conditions and quantification method were developed. Double extraction of the syringe with 0.5% ammonium hydroxide (pH 11), heat (75 °C), and sonication was able to efficiently extract 90% of the total tungsten from syringe. An inductively coupled plasma mass spectrometry method was qualified to selectively, accurately, and precisely quantify the extracted tungsten. The developed extraction and quantification method was acceptable in determining possible leachable tungsten from prefilled syringes.

Optimization Studies of Photocatalytic Tungsten-Doped Titania Coatings Deposited by Reactive Magnetron Co-Sputtering

In this article we investigate the structural and photocatalytic properties of W-doped titanium dioxide coatings. TiO2-W thin films were deposited onto glass slides by reactive magnetron co-sputtering. The properties of the films were analyzed using such techniques as XRD, Raman spectroscopy, EDX, TEM, and surface profilometry. The photocatalytic properties of the coatings were assessed using the methylene blue (MB) degradation test under UV and fluorescent light sources. The methylene blue decomposition experiments showed that, at the optimum dopant concentration of tungsten, the photocatalytic activity can be improved by a factor of 6, compared to undoped titania. For the coatings discussed within this work, the optimum dopant concentration was determined to be 5.89 at.% of W. The results indicated that tungsten doping at this level extends the lifetime of the photogenerated charge carriers and significantly increases the photocatalyst surface area.

Enhanced by-product desorption via laser assisted electron beam induced deposition of W(CO)6 with improved conductivity and resolution

Nanowires with higher tungsten (W) concentration and enhanced conductivity were grown via the laser assisted electron beam induced deposition (LAEBID) technique using tungsten hexacarbonyl W(CO)6 as the gas precursor. Periodic, pulsed laser irradiation facilitated CO desorption during growth by heating the deposit. Deposit purity improved with laser pulse width up to the threshold for pyrolytic laser chemical vapor deposition (LCVD). Higher resolution was also observed and was attributed to reduced CO incorporation and higher deposit density. The optimal composition and lowest resistivity was achieved by synchronizing the electron beam induced deposition and laser assist such that (1) the electron beam induced deposit is less than a monolayer per cycle and (2) the laser induced heating is just below the LCVD threshold.

Preparation of tungsten carbide nanoparticles by ion implantation and electrochemical etching

Glassy carbon (GC) substrates were implanted with 100keV tungsten ions at retained fluences of 4×1016 and 6×1016 ions/cm2 and surface-etched electrochemically in order to prepare tungsten-carbide (WC) nanoparticles on their topmost layers. The calculated current efficiency for the electrochemical etching was nearly the same for the two samples implanted at different fluences, suggesting the controllability of the etched depth using the consumed electric charge. The etching front reached the buried tungsten-implanted layer and increased the tungsten concentration at the surface. No oxidation of WC was observed, even under anodic potential application during electrochemical etching. The voltammogram response of the topmost nanoparticle layer was too small to be observed, probably due to the limited activity of the WC itself and the remaining low concentration. It was demonstrated that this technique could, in principle, be applied to various types of nanoparticle catalysts implanted in GC substrates.

25Cr-7Ni-2Mo-4W 슈퍼 2상 스테인리스강의 충격인성에 미치는 χ상의 영향

This study was carried out to investigate the precipitation behavior of the <TEX>${\chi}$</TEX> phase and the impact toughness of 25%Cr-7%Ni-2%Mo-4%W super duplex stainless steel. The <TEX>${\chi}$</TEX> phase was precipitated in the early stage of aging, and with the increasing aging time. However, after reaching a maximum value, the number decreased as a result of the gradual transformation of the <TEX>${\chi}$</TEX> phase into the <TEX>${\sigma}$</TEX>-phase. It was proved that the <TEX>${\chi}$</TEX> phase was an intermetallic compound, which represented a lower nickel concentration, higher chromium and molybdenum concentrations, and very higher tungsten concentration compared to the matrix phases. It also showed higher molybdenum and tungsten concentrations than the <TEX>${\sigma}$</TEX> phase. The decomposition of the ferrite phase into the <TEX>${\gamma}_2$</TEX> and <TEX>${\sigma}$</TEX> phases was retarded by W substitution for Mo. Thus, the number of <TEX>${\chi}$</TEX> phases increased. The impact value was decreased by the substitution of W for Mo. The impact toughness rapidly decreased with time when the <TEX>${\chi}$</TEX> phase began to precipitate in the initial stage of aging. The impact toughness was, therefore, greatly influenced for the precipitation of the <TEX>${\chi}$</TEX> phase.

Transparent and conductive W-doped SnO2 thin films fabricated by an aqueous solution process

High-quality transparent and conductive tungsten-doped tin oxide (SnO2:W) thin films with different thickness (from 60 to 600±10nm) were fabricated on quartz glass substrates by a solution-based method. A stable solution was prepared from tin chloride and ammonium tungstate together with polyvinyl alcohol as a film-forming promoter. It was found that all films showed homogeneous composition, smooth surface with no cracks and high transparency with the optical band gap ranging from 3.93 to 4.31eV. The effect of tungsten concentration, spin rate and annealing temperature on the morphological, electrical and optical properties of the films has been investigated. W doping has a large influence on the microstructure and the conductivity of the SnO2 thin films. The lowest resistivity of 2.8×10−3 Ω·cm was obtained for a SnO2: 3 at% W film, which was prepared at 3000rpm and annealed at 800°C in air. An eight-layer film with a sheet resistance of 60 Ω/□ and a thickness of 606nm could be fabricated by multiple coating operation, which still exhibited an optical transmittance of over 80% in the visible region from 400 to 700nm.

Influence of hydrogen and tungsten concentration on the tribological properties of DLC/DLC contacts with ZDDP

Diamond-like carbon (DLC) coatings are becoming potential candidates for automotive engine parts because of their excellent friction and wear resistance properties. It is important to understand their film-forming, friction reduction and wear resistance mechanisms. This paper studies the influence of hydrogen and tungsten concentration in DLCs on friction and wear by comparing the behaviour of one a-C, five a-C:H and four a-C:H:W coatings in DLC/DLC contacts lubricated with base oil and a ZDDP solution. a-C show lower boundary friction than the other types. W-DLCs experience higher wear compared to the other coatings. Over the range of concentrations studied, hydrogen and tungsten contents do not affect friction greatly but have a marked effect on adhesion, film-forming and wear properties.

Tungsten migration studies by controlled injection of volatile compounds

Volatile tungsten hexa-fluoride was locally injected into the TEXTOR tokamak as a marker for material migration studies. The injection was accompanied by puffing N-15 rare isotope as a nitrogen tracer in discharges with edge cooling by impurity seeding. The objective was to assess material balance by qualitative and quantitative determination of a global and local deposition pattern, material mixing effects and fluorine residence in plasma-facing components. Spectroscopy and ex situ ion beam analysis techniques were used. Tungsten was detected on all types of limiter tiles and short-term probes retrieved from the vessel. Over 80% of the injected W was identified. The largest tungsten concentration, 1×1018cm−2, was in the vicinity of the gas inlet. Co-deposits contained tungsten and a mix of light isotopes: H, D, He-4, B-10, B-11, C-12, C-13, N-14, N-15, O-16 and small quantities of F-19 thus showing that both He and nitrogen are trapped following wall conditioning (He glow) and edge cooling.

Toxicologic evaluation of tungsten: 28-day inhalation study of tungsten blue oxide in rats

The toxicity and toxicokinetics of tungsten blue oxide (TBO) were examined. TBO is an intermediate in the production of tungsten powder, and has shown the potential to cause cellular damage in in vitro studies. However, in vivo evidence seems to indicate a lack of adverse effects. The present study was undertaken to address the dearth of longer-term inhalation toxicity studies of tungsten oxides by investigating the biological responses induced by TBO when administered via nose-only inhalation to rats at levels of 0.08, 0.325, and 0.65 mg TBO/L of air for 6 h/day for 28 consecutive days, followed by a 14-day recovery period. Inhaled TBO was absorbed systemically and blood levels of tungsten increased as inhaled concentration increased. Among the tissues analyzed for tungsten levels, lung, femur and kidney showed increased levels, with lung at least an order of magnitude greater than kidney or femur. By exposure day 14, tungsten concentration in tissues had reached steady-state. Increased lung weight was noted for both terminal and recovery animals and was attributed to deposition of TBO in the lungs, inducing a macrophage influx. Microscopic evaluation of tissues revealed a dose-related increase in alveolar pigmented macrophages, alveolar foreign material and individual alveolar foamy macrophages in lung. After a recovery period there was a slight reduction in the incidence and severity of histopathological findings. Based on the absence of other adverse effects, the increased lung weights and the microscopic findings were interpreted as nonadverse response to exposure and were not considered a specific reaction to TBO.

The Strengthening of Weight Heavy Alloys During Heat Treatment

Abstract The results of studies of W-Ni-Co-Fe experimental alloy, with chemical composition assuring a possibility of producing Ni-based supersaturated solid solution are presented. The alloy was prepared from tungsten, nickel, cobalt and iron powders which were first mixed then melted in a ceramic crucible where they slowly solidified in hydrogen atmosphere. Next specimens were cut from the casting and heated at a temperature 950°C. After solution treatment the specimens were water quenched and then aged for 20 h at a temperature 300°C. The specimens were subjected to microhardness measurements and structure investigations. The latter included both conventional metallography and SEM observations. Moreover, for some specimens X-ray diffractometry studies and TEM investigations were conducted. It was concluded that quenching lead to an increase of tungsten concentration in nickel matrix which was confirmed by Ni lattice parameter increase. Aging of supersaturated solid solution caused strengthening of the Ni-based matrix, which was proved by hardness measurements. The TEM observation did not yield explicit proofs that the precipitation process could be responsible for strengthening of the alloy

In Vivo Tungsten Exposure Alters B-Cell Development and Increases DNA Damage in Murine Bone Marrow

High environmental tungsten levels were identified near the site of a childhood pre-B acute lymphoblastic leukemia cluster; however, a causal link between tungsten and leukemogenesis has not been established. The major site of tungsten deposition is bone, the site of B-cell development. In addition, our in vitro data suggest that developing B lymphocytes are susceptible to tungsten-induced DNA damage and growth inhibition. To extend these results, we assessed whether tungsten exposure altered B-cell development and induced DNA damage in vivo. Wild-type mice were exposed to tungsten in their drinking water for up to 16 weeks. Tungsten concentration in bone was analyzed by inductively coupled plasma mass spectrometry and correlated with B-cell development and DNA damage within the bone marrow. Tungsten exposure resulted in a rapid deposition within the bone following 1 week, and tungsten continued to accumulate thereafter albeit at a decreased rate. Flow cytometric analyses revealed a transient increase in mature IgD(+) B cells in the first 8 weeks of treatment, in animals of the highest and intermediate exposure groups. Following 16 weeks of exposure, all tungsten groups had a significantly greater percentage of cells in the late pro-/large pre-B developmental stages. DNA damage was increased in both whole marrow and isolated B cells, most notably at the lowest tungsten concentration tested. These findings confirm an immunological effect of tungsten exposure and suggest that tungsten could act as a tumor promoter, providing leukemic "hits" in multiple forms to developing B lymphocytes within the bone marrow.

Finding the Invisible Contaminants in CMOS Image Sensor Pixels: The DCS Technique

Abstract This article discusses the basic principles of dark current spectroscopy (DCS), a measurement technique that can detect and identify low levels of metal contaminants in CMOS image sensors. An example is given in which DCS is used to determine the concentration of tungsten and gold contaminants in an image sensor and estimate the dark current generated by a single atom of each metal.

Recovery of Tungsten (VI) from Aqueous Solutions by Complexation-ultrafiltration Process with the Help of Polyquaternium

Polyquaternium-6 (PQ6) as the water-soluble polymer was used for complexing the anion forms of tungsten (VI) before ultrafiltration. Tungsten (VI)-PQ6 complex was retained by polysulfone hollow fiber ultrafiltration membrane in the complexation-ultrafiltration process. Effects of various operating parameters such as polymer metal ratio(PMR), pH and chloride ion concentration on permeate flux (J) and tungsten rejection coefficient (R) were investigated. The integration of four experiments including concentration, decomplexation, diafiltration and reuse of regenerated polymer was carried out. In the process of concentration, J declines slowly and R is about 1 at PMR of 3 and pH of 7. Tungsten concentration in the retentate increases linearly with volume concentration factor. Tungsten is concentrated efficiently with the membrane. The concentrated retentate was used further for the decomplexation. It takes about 6 min to reach the decomplexation equilibrium at chloride ion concentration of 50 mgL−1. The decomplexation percentage of tungsten (VI)-PQ6 complex reaches 56.1%. In the diafiltration process, tungsten (VI) can be extracted effectively by using 50 mgL−1 chloride ion solution, and the purification of the regenerated PQ6 is acceptably satisfactory. The regenerated PQ6 was used to bind tungsten (VI) at various pH values. The binding capacity of the regenerated PQ6 is close to that of fresh PQ6, and the recovery percentage of binding capacity is higher than 90%.

Potentiodynamic Polarization Behaviour of Electroless Ni-P-W Coatings

This paper deals with the synthesis of electroless Ni-P-W coatings on mild steel substrate followed by furnace-annealing process. Corrosion behaviors of the coatings after heat treatments at various annealing temperatures are evaluated by potentiodynamic polarization test using 3.5% sodium chloride solution. The electrochemical parameters, that is, corrosion potential and corrosion current density, are optimized for maximum corrosion resistance using Taguchi-based grey relational analysis, considering four coating parameters, namely, concentration of nickel, concentration of reducing agent, concentration of tungsten, and annealing temperature as main design factors. The optimum combination of these four design factors is obtained from the analysis. The analysis of variance reveals that the concentration of tungsten source and annealing temperature play the most important role on the corrosion performance of the coating. Effects of the operating parameters on microstructures, in terms of porosity formation, crystallization, phase transformation, grain growth, are investigated using SEM, EDX, and XRD techniques.

Analysis of mineral nutrients status of whole plant and growth substratum of Phyllanthus niruri L., an anti-plasmodial herb using Instrumental Neutron Activation Analysis

The mineral status of whole plant samples of Phyllanthus and its growth substratum was determined using Instrumental Neutron Activation Analysis. A total of 11 elements were detected in both whole plant and soil samples with varying concentrations depending on area of collection as well plant or it soil substratum. Comparatively, the concentration of all the elements except Cl, Ca and Br was higher in the soil samples than the whole plant indicating that the plant obtained these elements from the growth substratum. For the plant samples, the concentration of tungsten (W) and arsenic (As) were below the detection limits while for the soil sample chlorine (Cl) and calcium (Ca) were below detection limits. Three of the elements namely Mg, Ca and K detected in the plant samples are macroelements and were therefore detected in higher concentrations in the plant samples. The element with the highest concentration was K and it ranged from 1,215.44 to 5,658.06 and 0.64 to 1.20 % in soil and whole plant samples respectively. Arsenic (As) is considered as a toxic element and its concentration below detection limits in the whole plant sample makes it pharmacologically safe for human consumption.

Electrodeposited nanostructured WO3 thin films for photoelectrochemical applications

Thin films of WO3 were deposited on FTO-coated glass substrates by electrodeposition using aqueous solutions of peroxotungstic acid. The effects of varying the tungsten concentration of peroxotungstic acid and deposition time on the mineralogical, microstructural, morphological, optical, and photoelectrochemical properties were determined using X-ray diffraction, scanning electron microscopy, focused ion beam milling, UV–vis spectrophotometry, and linear potentiodynamic voltammetry, respectively. The films consisted of monoclinic WO3 of grain sizes in the range 77–122nm and thicknesses in the range 258–1394nm; the true porosities were <5%. These microstructural and morphological parameters depended largely upon the tungsten concentration and deposition time. Some preferred orientation was observed and this was considered to result from crystallographic and microstructural factors. The optical transmission data revealed significant decreases in the optical indirect band gap, from 3.05eV to 2.60eV, as a function of increasing film thickness. This was considered to result from differential contributions from the surface and bulk band gap components as well as compressive stress. The voltammetry data and associated Butler plot revealed the establishment of a Schottky depletion layer and a flat-band potential of +0.2V to +0.3V versus Ag/AgCl. Although the calculated photoconversion efficiencies were in the range 0.02–0.14%, which is commensurate with the use of a tungsten–halogen light rather than xenon, there was a trend of increasing efficiency as a function of increasing film thickness. This was attributed to decreasing band gap and increasing light absorption. The shape of the curve of the preceding data supports the conclusion of differential contributions from the surface and bulk band gap components. Finally, evidence of photolysis in the absence of an external applied potential suggests the importance of the effect of grain size on the pH and its alteration of the flat-band potential.

Microstructural Evolution and Mechanical Properties under High Strain Rate Testing of W&amp;ndash;3.99Ni&amp;ndash;1.71Fe Sintered by a Two-Stage Sintering Process

A two-stage sintering practice was applied to W­3.99Ni­1.71Fe (mass%) to control its microstructural evolution and, accordingly, mechanical properties under high strain rates. Unlike the traditional one-stage liquid phase sintering, the alloy was first solid-state-sintered to close to full densification, and then liquid-phase-sintered by induction heating where the cooling rate was fast. With the two-stage sintering, the growth of tungsten grains and the contiguity of tungsten grains could be closely tailored, and a high dissolved tungsten concentration in the matrix phase could be maintained. All of these microstructural characteristics led to enhanced mechanical properties of this alloy tested under high strain rates. [doi:10.2320/matertrans.M2012027]

Inhibition of Tungsten-Induced Protein Aggregation by Cetyl Trimethyl Ammonium Bromide

TECHNICAL ABSTRACT: The purpose of this work was to investigate a potential mechanism for the inhibition of tungsten-mediated monoclonal antibody (mAb) biophysical modifications and sub-visible particle formation. A 1 mg/mL mAb formulated in 150 mM NaCl, 20 mM histidine, pH 6.0, was incubated with 1, 37, and 100 ppm of tungsten polyanions in the form of sodium tungstate both in the presence and absence of the anionic surfactant and chelating agent diethylene triamine pentaacetic acid (DTPA) or the cationic surfactant cetyl trimethyl ammonium bromide (CTAB) for 24 h at 25 °C. Assays including pH, UV-Vis spectroscopy, size exclusion chromatography, intrinsic tryptophan/tyrosine fluorescence, and micro-flow imaging were performed to assess the impact on short-term mAb stability and aggregation. We conclude that the use of micromolar concentrations of the formulation excipient and cationic surfactant CTAB equivalent to the anticipated tungsten concentration in solution effectively inhibits loss of protein concentration, fragmentation, changes in intrinsic fluorescence intensity, and the formation of sub-visible particles. The purpose of this work was to investigate a potential mechanism for the inhibition of tungsten-mediated monoclonal antibody (mAb) biophysical modifications and sub-visible particle formation. A mAb formulation was incubated with tungsten polyanions in the presence and absence of the anionic surfactant and chelating agent diethylene triamine pentaacetic acid (DTPA) or the cationic surfactant cetyl trimethyl ammonium bromide (CTAB). Formulation was characterized by pH, UV-Vis spectroscopy, size exclusion chromatography, intrinsic tryptophan/tyrosine fluorescence, and micro-flow imaging. We conclude that the formulation excipient and cationic surfactant CTAB effectively inhibits biophysical modifications and sub-visible particle formation.

Additional analysis of dendrochemical data of Fallon, Nevada

Previously reported dendrochemical data showed temporal variability in concentration of tungsten (W) and cobalt (Co) in tree rings of Fallon, Nevada, US. Criticism of this work questioned the use of the Mann–Whitney test for determining change in element concentrations. Here, we demonstrate that Mann–Whitney is appropriate for comparing background element concentrations to possibly elevated concentrations in environmental media. Given that Mann–Whitney tests for differences in shapes of distributions, inter-tree variability (e.g., “coefficient of median variation”) was calculated for each measured element across trees within subsites and time periods. For W and Co, the metals of highest interest in Fallon, inter-tree variability was always higher within versus outside of Fallon. For calibration purposes, this entire analysis was repeated at a different town, Sweet Home, Oregon, which has a known tungsten-powder facility, and inter-tree variability of W in tree rings confirmed the establishment date of that facility. Mann–Whitney testing of simulated data also confirmed its appropriateness for analysis of data affected by point-source contamination. This research adds important new dimensions to dendrochemistry of point-source contamination by adding analysis of inter-tree variability to analysis of central tendency. Fallon remains distinctive by a temporal increase in W beginning by the mid 1990s and by elevated Co since at least the early 1990s, as well as by high inter-tree variability for W and Co relative to comparison towns.

Selected Trace Elements in the Sacramento River, California: Occurrence and Distribution

The impact of trace elements from the Iron Mountain Superfund site on the Sacramento River and selected tributaries is examined. The concentration and distribution of many trace elements-including aluminum, arsenic, boron, barium, beryllium, bismuth, cadmium, cerium, cobalt, chromium, cesium, copper, dysprosium, erbium, europium, iron, gadolinium, holmium, potassium, lanthanum, lithium, lutetium, manganese, molybdenum, neodymium, nickel, lead, praseodymium, rubidium, rhenium, antimony, selenium, samarium, strontium, terbium, thallium, thulium, uranium, vanadium, tungsten, yttrium, ytterbium, zinc, and zirconium-were measured using a combination of inductively coupled plasma-mass spectrometry and inductively coupled plasma-atomic emission spectrometry. Samples were collected using ultraclean techniques at selected sites in tributaries and the Sacramento River from below Shasta Dam to Freeport, California, at six separate time periods from mid-1996 to mid-1997. Trace-element concentrations in dissolved (ultrafiltered [0.005-μm pore size]) and colloidal material, isolated at each site from large volume samples, are reported. For example, dissolved Zn ranged from 900μg/L at Spring Creek (Iron Mountain acid mine drainage into Keswick Reservoir) to 0.65μg/L at the Freeport site on the Sacramento River. Zn associated with colloidal material ranged from 4.3μg/L (colloid-equivalent concentration) in Spring Creek to 21.8μg/L at the Colusa site on the Sacramento River. Virtually all of the trace elements exist in Spring Creek in the dissolved form. On entering Keswick Reservoir, the metals are at least partially converted by precipitation or adsorption to the particulate phase. Despite this observation, few of the elements are removed by settling; instead the majority is transported, associated with colloids, downriver, at least to the Bend Bridge site, which is 67km from Keswick Dam. Most trace elements are strongly associated with the colloid phase going downriver under both low- and high-flow conditions.