Presence Of Organic Impurities Research Articles

Effect of Rapid Thermal Annealing on CuO Nanoparticles

Abstract This work is a comparative study of the effect of two different annealing methods on copper oxide (CuO) nanoparticle properties obtained previously by direct precipitation method. The prepared samples were annealed in air at various temperatures (300, 400, 500°C) for 1 hour. Then they were characterized by employing scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Visible, and Fourier Transform Infrared (FT-IR) spectroscopy. The main results revealed an increase in the grain size in both methods as the annealing temperature increases. It reaches 30.93 nm in RTA and 26.75 nm in STA at 500°C. XRD spectra showed, in the case of RTA at 500 °C, a significant decrease in the intensity corresponding to the (002) and (111) orientations. This result indicated that beyond 400 °C, one hour of RTA is not suitable for enhancing CuO nanoparticle crystallinity compared to STA. The optical analysis demonstrated that the energy of the optical band gap in STA is higher than that in RTA. It reaches 2,88 eV at 500°C using RTA which is close to the gap value of CuO in the range of 1.8–2.8 eV. FT-IR results showed, for both methods, the presence of characteristic peaks of the Cu-O bonds in the monoclinic CuO structure without any trace of Cu2O structure. Nevertheless, samples exposed to RTA for one hour are more susceptible to absorbing species of C=O bond (C=O bond is due to the atmospheric CO2 absorption and the presence of organic impurities from the synthesis process) than those of STA. Hence, RTA at 500 °C is far from producing CuO nanoparticles with preferred characteristics; it needs further research to examine the effect of higher temperature by controlling the annealing time.

Pengembangan Dan Validasi Metode Analisis Amlodipin Besilat Dan Cemarannya Dalam Sediaan Tablet

Amlodipine besylate belongs to the class of oral dihydropyridine calcium channel blockers that can be used to hypertension and angina therapy. Amlodipine as a pharmaceutical preparation must meet the criteria for a good pharmaceutical preparation, namely safe, efficacious and quality. In terms of safety, the presence of organic impurity in pharmaceutical products can affect the safety of medicinal products. Because the difficultness to obtain a standard of impurity, it is necessary to develop an analytical method to analyze the presence of contamination by stress testing. The analytical method was developed using a High Performance Liquid Chromatography (HPLC) instrument with Eclipse Plus C18 column 5 m (150 x 4.6 mm), mobile phase triethylamine (TEA): methanol in a ratio of 40:60 with isocratic elution and a flow rate of 1 mL/minutes and a wavelength of 237 nm with an injection volume of 10 µL. The results of the method validation showed good linearity with R2 of 0.9996, detection limit of 18.46 µg/mL and quantization limit value of 61.54 µg/mL. The value of the coefficient of variation on the precision parameter is 1.18-1.26%. The percent recovery accuracy value is 93.07-105.44% and the range value for proportional samples is in the concentration range of 24-84 µg/ml with R2 = 0.9993. The HPLC system meets all requirements for acceptance of the system conformity test. The results of this experiment showed that there were 2 out of 5 peaks of degradation products whose chemical structure was known. The application of the analytical method on commercial samples showed levels between 90.79-95.68% and there was no impurity in the product samples.

Characteristics of the Nucleation Process in a Model Solution of Synovial Fluid in the Presence of Organic Impurities

Characteristics of the Nucleation Process in a Model Solution of Synovial Fluid in the Presence of Organic Impurities

The Affinity of Human Fetal Osteoblast to Laser-Modified Titanium Implant Fixtures

Introduction: Implant surface modification methods have recently involved laser treatment to achieve the desired implant surface characteristics. Meanwhile, surface modification could potentially introduce foreign elements to the implant surface during the manufacturing process. Objectives: The study aimed to investigate the surface chemistry and topography of commercially available laser-modified titanium implants, together with evaluating the cell morphology and cell adhesion of human fetal osteoblast (hFOB) seeded onto the same implants. Method: Six (6) samples of commercially available laser-modified titanium implants were investigated. These implants were manufactured by two different companies. Three (3) implants were made from commercially pure grade 4 Titanium (Brand X); and three were made from grade 5 Ti6Al4V (Brand Y). The surface topography of these implants was analyzed by scanning electron microscope (SEM) and the surface chemistry was evaluated with electron dispersive x-ray spectroscopy(EDS). Human fetal osteoblasts were seeded onto the implant fixtures to investigate the biocompatibility and adhesion. Results & Discussion: Brand X displayed dark areas under SEM while it was rarely found on brand Y. These dark areas were consistent with their organic matter. The hFOB cell experiments revealed cell adhesion with filopodia on Brand X samples which is consistent with cell maturation. The cells on Brand Y were morphologically round and lacked projections, one sample was devoid of any noticeable cells under SEM. Cell adhesion was observed early at 48 hrs in laser-irradiated titanium fixtures from both the brands. Conclusion: The presence of organic impurities in Brand X should not be overlooked because disruption of the osseointegration process may occur due to the rejection of the biomaterial in an in-vivo model. Nevertheless, there was insufficient evidence to link implant failure directly with carbon contaminated implant surfaces. Further studies to determine the toxicity of Vanadium from Ti6Al4V in an in-vivo environment should indicate the reason for different cell maturation.

Surface Chemistry Analysis of Carbon Nanotube Fibers by X‐Ray Photoelectron Spectroscopy

Carbon nanotube (CNT) fibers are materials with an exceptional combination of properties, including higher toughness than carbon fibers, electrical conductivity above metals, large specific surface area (250 m2 g−1), and high electrochemical stability. As such, they are a key component in various multifunctional structures combining augmented mechanical properties with efficient interfacial energy storage/transfer processes. This work presents a thorough XPS study of CNT fibers subjected to different purification and chemical treatments, including spatially‐resolved micro XPS synchrotron measurements. The dominant feature is an inherently high degree of sp2 conjugation, leading to a strong plasmonic band and a semi‐metallic valence band lineshape. This high degree of CNT perfection in terms of longitudinal “graphitization” helps to explain reported bulk properties including the high electrical and thermal conductivity, and accessible quantum capacitance. There is also presence of organic impurities, mostly heavy carbonaceous molecules formed as by‐products during fiber synthesis and which are adsorbed on the CNTs. Sulfur, a promoter used in the CNT growth reaction, is found both in these surface impurities and associated with the Fe catalyst. The observation of strongly‐adsorbed surface impurities is consistent with the high ductility of CNT fibers, attributed to interfacial lubricity.

Reactivity of concentrated ammonium nitrate solutions in the presence of organic impurities

Assessment of mixtures reactivity under certain conditions is essential for safe and conscious designing and improving manufacturing processes. One commonly used compound, the reactivity of which is very important, is ammonium nitrate and its solutions. The biggest influence on the reactivity of ammonium nitrate has the temperature and presence of other compounds, including impurities, that catalyze reactions leading to degradation. One of such impurities are organic compounds which impact on the ammonium nitrate has not yet been clearly described. The aim of the research was to investigate the influence of selected organic impurities on the reactivity of aqueous solutions containing up to 50 wt % ammonium nitrate, buffered with 15 wt % diammonium phosphate. The measurements were carried out using differential scanning calorimetry. Solution without organic compounds showed no reactivity up to 240 C. The addition of 8 wt % ammonium oxalate did not increase the reactivity of ammonium nitrate. It was observed an endothermic decomposition reaction of oxalic acid, beginning at 185 C. During the measurement of a solution containing 6 wt % phenidone, it was registered an exothermic complex reaction, beginning at 189 C and showing relatively small thermal effect. Addition of 6 wt % pyrogallol caused a significant increase in reactivity of ammonium nitrate solution. Strongly exothermic reaction beginning at 192 C was observed. Spectrophotometric measurement showed a clear nitrate concentration loss in the sample after calorimetric measurement. The results show that the nitrate ion selectively oxidizes certain functional groups in organic compounds.

Room-Temperature Conversion of Soybean Oil and Poultry Fat to Biodiesel Catalyzed by Nanocrystalline Calcium Oxides

A promising route for the production of biodiesel (fatty acid methyl esters, FAMES) via transesterification of soybean oil (SBO) and poultry fat with methanol in quantitative conversions at room temperature has been developed using nanocrystalline calcium oxides as catalysts. Under the same conditions, laboratory-grade CaO gave only 2% conversion in the case of SBO, and there was no observable reaction with poultry fat. The soybean oil/methanol ratio in our protocol is 1:27. With our most active catalyst, deactivation was observed after eight cycles with SBO and after three cycles with poultry fat. Deactivation may be associated with one or more of the following factors: the presence of organic impurities or adventitious moisture and enolate formation by the deprotonation of the carbon alpha to the carboxy group in the triglyceride or FAMES. The biodiesel from our protocol meets the ASTM D-874 standard for sulfated ash for both substrates.

Photolytic degradation of chlorinated phenols in room temperature ionic liquids

The photolytic degradation of 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,5-tetrachlorophenol (2,3,4,5-TeCP) and pentachlorophenol (PCP) in 1-butyl-3-methylimidazolium hexafluorophosphate {[bmim +]PF 6 −} and 1-ethyl-3-methylimidazolium bis(perfluoroethylsulfonyl)imide {[emim +]beti} room temperature ionic liquids (RTILs) has been investigated using UV radiation of 253.7 nm. Stability study revealed that these RTILs are relatively resistant to phototransformation when used as pure phases. At low concentrations (less than 1.57 mM), chlorinated phenols could be degraded in these RTILs following pseudo-first-order kinetics. Intermediate product identification using Electrospray TOF MS, GC–MS and HPLC revealed the formation of phenol among the stable phototransformation intermediates of 2-CP. It is proposed here that two possible pathways, via formation of phenoxyl radical or carbene, could lead to phenol generation. In these two mechanisms, {[bmim +]PF 6 −} may participate in the reaction as H-donor. The increase of the chlorine atoms in the phenolic ring generally resulted in a decrease in the phototransformation rates, with exception of 2,4,6-TCP. UV absorbing impurities present in the ionic liquids as received from the manufacturer had a significant negative effect on the phototransformation rate of chlorophenols. Purification of RTILs using activated carbon enhanced the photodegradation rates. On the other hand, these impurities could, at some extent, protect the ionic liquid from photolysis and enhance the stability of the solvent. Recyclability study indicated that the recycling of the solvents was hindered at some extend by the presence of organic impurities that were resistant to photolysis or by the generation of byproducts that were resistant to photolytic degradation and compete with the chlorophenols for photon absorption. While further research is necessary to examine all aspects of this system, including the use of non-toxic RTILs, it is feasible that this technology can be further developed into a two-step process for extraction of organic pollutants from solid matrices, such as contaminated soils or dredged sediments, using ionic liquid solvents followed by in situ photodegradation of the organic contaminants in the ionic liquid extractant phase while achieving simultaneously regeneration of the solvent.

Electrowinning of cobalt from sulphate solutions contaminated with organic impurities

The electrowinning (EW) of cobalt from sulphate solution contaminated with organic impurities: tri- n-butyl phosphate (TBP), 2-hexylmethyl decanoic acid (VERSATIC 10), 2-hydroxy-5-nonyl acetophenone oxime (LIX 84), di-2-ethylhexyl phosphoric acid (D2EHPA) and di-2,4,4-trimethylpentyl phosphinic acid (CYANEX 272) has been investigated at 60 °C. Both cyclic voltammetry and flow cell electrolysis have been used. The effect of organic impurities on the cathodic reduction of cobalt is compared with the blank solution. The current efficiency is more than 90% in most cases and is highest in the case of D2EHPA (96%) and lowest with VERSATIC 10 (86%). The cathodic polarization from cyclic voltammetry indicates that the exchange current density ( i 0) value is higher in the presence of organic impurities than in solutions containing no organic impurities. The organic impurities indicate an inhibition of electrocrystallization process due to suppression of nucleation. Cathodic polarization also indicates that Co 2+ reduction occurs slightly at less negative potential in solution containing organic impurities.

Processing and characterisation of sol-gel glasses and powders in the system TeO2-TiO2

Sol-gel processing routes have been developed for the production of thin films and powders in the system TeO2-TiO2 from tellurium and titanium alkoxides. The structure and properties of the resultant materials have been characterised as a function of heat treatment temperature. Pure sol-gel derived TeO2 thin films are difficult to prepare with good optical transparency due to the presence of organic impurities and/or a highly dispersed metallic tellurium phase when heated at temperatures up to approximately 340°C, with crystallisation to α-TeO2 occurring when the heat treatment temperature is further increased. Additions of TiO2 were found to retard the crystallisation of the α-TeO2 but promote the formation of other TiO2 or TiTe3O8 phases. However, an optimum composition in the range 0.9TeO2 0.1TiO2 was identified, which allows optically transparent thin films to be prepared with high refractive index and offers the potential for practical device manufacture.

Sol-derived Pd/SiO 2 catalyst: characterization and activity in benzene hydrogenation

Pd/SiO 2 catalysts were prepared by adsorption of Pd sols on support Aerosil 200 and characterized by transmission electron microscopy (TEM), CO chemisorption and temperature programmed oxidation (TPO). The Pd hydrosols were generated from PdCl 2 solution and ethanol as reducing agent in the presence of poly(diallyldimethylammonium chloride), PDDA. The pH of the solution was increased to ensure adsorption of the Pd sol with high concentration of PDDA. The catalytic activity was tested in benzene hydrogenation. The presence of organic impurities and the role of morphology affecting the activity have been discussed in terms of the preparation procedure applied.

LIRIC 3.2 an updated model for iodine behaviour in the presence of organic impurities

Library of iodine reactions in containment (LIRIC) is a comprehensive mechanistic model for the chemical and mass transport behaviour of iodine in containment under postulated nuclear reactor accident conditions. The LIRIC model has successfully simulated the iodine behaviour in experiments performed under conditions relevant to post-accident containment, and some of the results have been published previously. This document describes the latest version of the model, LIRIC 3.2, and presents simulation results of a few integrated tests performed in the Radioiodine Test Facility.

Effect of organic impurities on the surface morphology and growth mechanism of KBP crystals (C8H5O4K)

The surface morphology of the (010) face of potassium biphthalate (KBP) crystals grown from aqueous solutions under the supersaturation ranging within 0.029–0.04 has been studied by the methods of optical and electron microscopies. It was revealed that the (010) surface has polygonal growth macrohills of the dislocation nature, small hillocks developing by the mechanism of successive two-dimensional nucleation, and numerous two-dimensional nuclei. The density of small hillocks (104–105 cm−2) exceeds the dislocation density in KBP crystals by one to two orders of magnitude. It is shown that at low supersaturations, the (010) face grows simultaneously by the dislocation mechanism and the mechanism of successive two-dimensional nucleation. It is also established that the tangential velocity of growth-step motion on the (010) face increases in the presence of organic impurities. This effect can be used as one of the factors increasing the growth rates of crystal faces at low impurity concentrations (the so-called catalytic effect of impurities).

Cross-polarization of fullerenes (C60 and C70) in the presence of organic impurities

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCross-polarization of fullerenes (C60 and C70) in the presence of organic impuritiesJohn V. Hanna and Michael A. WilsonCite this: J. Phys. Chem. 1992, 96, 16, 6518–6523Publication Date (Print):August 1, 1992Publication History Published online1 May 2002Published inissue 1 August 1992https://doi.org/10.1021/j100195a002RIGHTS & PERMISSIONSArticle Views70Altmetric-Citations10LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (657 KB) Get e-Alerts

Evaporation studies and phase stability of mercuric iodide

Some aspects of the mass spectrometric analysis of a molecular beam of mercuric iodide relevant to the vapor growth of HgI 2 crystals are discussed. Mercuric iodide evaporates non-dissociatively in the temperature range of 35–150°C. Hydrocarbons and water are the main volatile impurities. It has been shown that hydrocarbons can be introduced in mercuric iodide not only by iodine but also by contamination by oil vapors from rotary vacuum pumps. Nonstoichiometry of mercuric iodine towards either excess of iodine or excess of mercury has been found. The nonstoichiometry is stabilized by the presence of organic impurities. The vapor pressure curve of HgI 2 shows an abrupt change in sublimation enthalpy at 67°C possibly due to a surface reconstruction at this temperature. As the growth temperature of the HgI 2 crystals is much higher, it is expected that the crystals will acquire an appreciable concentration of surface defects. This is in agreement with earlier observations of HgI 2 detector manufacturers.

Tunneling Conductance of Asymmetrical Barriers

The voltage-dependent tunneling conductance of trapezoidal potential barriers has been calculated using two extreme models of (1) the WKB approximation and (2) perfectly sharp boundaries between the metal electrode and the insulator. We show that for both models the conductance-voltage plot is roughly parabolic at low voltages (≲0.4 V). The minimum conductance is not at zero bias unless the barrier is symmetrical and identical Fermi energies are chosen for the two metal electrodes. The inclusion of image forces does not radically alter the shape of the conductance-voltage dependence. Using reasonable barrier shapes, the asymmetry of the calculated conductance about V=0 is not as large as we frequently observe experimentally. We point out that this extreme asymmetry appears to be associated with the presence of organic impurities in the oxide layer of the junction.

VII.—Optically Positive Cordierite

Cordierite was first found in Travancore at Teruwulla (lat. 9° 22′ N. and long. 76° 37′ E.) in a kind of diorite. In the hand-specimen the mineral appears as violet patches and spots. Monazite, magnetite or ilmenite, garnet and biotite with probably a little hornblende, occur in association with it. In the sections the mineral is found to contain numerous globular inclusions which are surrounded by pleochroic halos. The larger of these may be identified as monazite under the microscope. The mineral is itself pleochroic, light vibrating in the direction of the axis of mean velocity (Y) showing a pronounced violet tint. When light vibrates in other directions the plates do not show any distinct colour, but a faint yellow tint may be observed in some plates. When light vibrates in the direction of the Y axis the pleochroic halos round the inclusions disappear and assume the violet tint of the crystal plate. Cordierite is supposed to occur usually in metamorphosed sediments, and the pleochroic halos are regarded as due to the presence of organic impurities. But a sedimentary origin is out of the question in the present case. It is held by some that pleochroic halos are due to the presence of radio-active substances. I kept an Ilford Empress photographic plate exposed in a dark box to a crushed sample of the mineral for more than twelve hours, but on development the plate did not show any indication of having been affected by the mineral.