Amount Of Metallic Impurities Research Articles

A Review on Metal Impurities in Pharmaceuticals

Sources of metal impurities can from anywhere in drug product as raw material which may produce using metal catalyst, excipients, process materials, Water or any solvent used, manufacturing equipment, environment, packaging materials. So, it leads to metal impurity in high amount present in final drug product that is why it is important to check the impurity level in final drug product or as well as in process also that it should be present in low or acceptable amount. Any Drug product is not completely pure, some amount of metal impurities are always present in pharmaceutical product may cause various toxicity when it will be administered. Thus it is necessary to check impurity level is present at acceptable amount. The present review gives an account of updated information about metal impurities and reviews the regulatory aspects for such metal impurities in drug substance/drug product. In addition the aim of this article is to discuss the currently used different analytical techniques for detection of metals from drug product like spectrophotometry, X – Ray florescence spectrometry, AAS, INAA, ICP – AES, ICP – MS, MP – AES, Laser Ablation – ICP – MS etc which is used for quality control of metal impurities in pharmaceuticals.

Towards the optimization of carbon nanotube properties via in situ and ex situ studies of the growth mechanism

The synthesis conditions of multi-walled carbon nanotubes (MWCNTs) indirectly determine their application potential through the decisive role in the characteristics of individual tubes: diameter distribution, structure and defectiveness of graphene walls, the amount of metal impurities and amorphous carbon. In the present work, we have studied the influence of the catalyst composition and synthesis conditions on the diameter distribution and the structure of nanotube walls. We have observed the influence of the particle size for MWCNT synthesis (i.e. size effect) on catalytic activity by ex situ and in situ techniques: in situ X-ray diffraction on synchrotron radiation (SRXRD), gas chromatography, and ex situ transmission electron microscopy. The data obtained by in situ SRXRD are in agreement with the results collected using laboratory tubular fix-bed catalytic reactor allowing thereby extending the applicability of the approach. For the first time we have shown the increase of the fraction of graphene walls in the total MWCNT diameter with time.

Plausible role of nanoparticle contamination in the synthesis and properties of organic electronic materials

AbstractTraceless transition metal catalysis (Pd, Ni, Cu, etc.) is very difficult to achieve. Metal contamination in the synthesized products is unavoidable and the most important questions are: How to control metal impurities? What amount of metal impurities can be tolerated? What is the influence of metal impurities? In this brief review, the plausible origins of nanoparticle contamination are discussed in the framework of catalytic synthesis of organic electronic materials. Key factors responsible for increasing the probability of contamination are considered from the point of view of catalytic reaction mechanisms. The purity of the catalyst may greatly affect the molecular weight of a polymer, reaction yield, selectivity and several other parameters. Metal contamination in the final polymeric products may induce some changes in the electric conductivity, charge transport properties, photovoltaic performance and other important parameters.

Selective leaching of lead from a lead–silver–zinc concentrate with hydrogen peroxide in citrate solutions

Selective leaching of lead from a Pb–Ag–Zn concentrate with hydrogen peroxide in citrate solutions was studied at room temperature. Leaching tests were performed, varying the H2O2 concentration and the solid–liquid ratio, holding the solution pH constant at 7 and the citrate concentration at 1M. Lead extractions of 100% were achieved with four and five times the stoichiometric quantity needed to form elemental sulphur, with only a small amount of metal impurities dissolved (Ag, Zn and Fe). The lead solubility limit at those conditions was found to be ∼24 g Pb(II) L− 1. X-ray diffraction analyses of the leach residues were free of galena (PbS), while other metal sulphides, such as sphalerite (ZnS), chalcopyrite (CuFeS2) and pyrite (FeS2), were basically unaffected.

The role of steam treatment on the structure, purity and length distribution of multi-walled carbon nanotubes

Purification and shortening of carbon nanotubes have attracted a great deal of attention to increase the biocompatibility and performance of the material in several applications. Steam treatment has been employed to afford both purification and shortening of multi-walled carbon nanotubes (MWCNTs). Steam removes the amorphous carbon and the graphitic particles that sheath catalytic nanoparticles, facilitating their removal by a subsequent acidic wash. The amount of metal impurities can be reduced in this manner below 0.01wt.%. The length distribution of MWCNTs after different steam treatment times (from 1h to 15h) was assessed by box plot analysis of the electron microscopy data. Samples with a median length of 0.57μm have been prepared with the reported methodology while preserving the integrity of the tubular wall structure.

The MWCNTs-Rh Nanocomposite Obtained By The New High-Temperature Method

AbstractA nanocomposite was fabricated during the research undertaken, consisting of multiwalled carbon nanotubes coated with rhodium nanoparticles by the new high-temperature method being the subject of the patent claim. High quality multiwalled carbon nanotubes (MWCNTs) with the length of 100÷500 nm and the diameter of 8÷20 nm obtained in advance with Catalytic Chemical Vapour Deposition (CVD) were employed in the investigations. The nanotubes manufactured under the own research contain small amounts of metallic impurities and amorphous carbon deposits. Multiwalled carbon nanotubes functionalisation in acids was applied to deposit rhodium nanoparticles onto the surface of carbon nanotubes, and then the material was placed in a solution being a precursor of rhodium nanoparticles. The material prepared was next placed in a quartz vessel and subjected to high-temperature reduction in the atmosphere of argon to deposit rhodium nanoparticles onto the surface of multiwalled carbon nanotubes. The following examinations were performed, respectively: MWCNTs fabrication, fabrication of a CNT-NPs (Carbon NanoTube-NanoParticles) nanocomposite material; the characterisation of the materials produced including examination of the structure and morphology, and the assessment of rhodium nanoparticles distribution on the surface of carbon nanotubes. Micro- and spectroscopy techniques were employed to characterise the structure of the nanocomposites obtained.

Influence of oily wastes on the pyrolysis of scrap tire

The co-pyrolysis of scrap tires with oily wastes from ships (bilge water oil and oily sludge) was studied to investigate the effect of oily wastes on the pyrolysis of scrap tire. Co-pyrolysis experiments were carried out in a fixed bed reactor in the absence and the presence of catalyst at 500°C. The catalysts used in the pyrolysis were a commercial refinery catalyst and an industrial by-product containing iron. The fuel characteristics and chemical compositions of pyrolysis products were characterized by means of chromatographic, spectroscopic and standard ASTM methods. Although, the oily wastes did not affect the product yields from the pyrolysis of scrap tire, they improved the fuel characteristics of scrap tire derived oils. The fuel characteristics of co-pyrolysis oils (except flash point and sulfur content) had similar fuel characteristic with the commercial diesel. It was also found that the amounts of metal impurities in all pyrolytic oils were smaller than 0.3ppm, which was a significantly low amount compared with those in the original oily wastes. Gross calorific values of pyrolysis gases were found to be in the range of 20.4–26.4MJNm−3. It was concluded that co-pyrolysis of scrap tire with oily wastes could be an environmentally friendly way for the conversion of disposable and hazardous wastes such as scrap tires, bilge water oil and oily sludge into fuels.

Effect of edge plane sites, oxygenated species and metallic impurities upon the electroactivity of carbon nanotube-modified electrodes toward hydrazine

The effect of edge plane sites, oxygenated species and metal oxide nanoparticles upon the electroactivity toward hydrazine observed in glassy carbon electrodes (GCEs) modified with multi-walled carbon nanotube (CNT) films has been examined. Voltammetric and amperometric experiments have revealed the importance of edge plane and oxygenated species within the surface of GCE, edge plane pyrolytic graphite and CNT-modified GCE electrodes in the overpotential, sensitivity and stability observed in their electrochemical response. The effect of iron oxide nanoparticles, typically found as the major impurity in CNT, was moderate and can be neglected using a voltammetric pretreatment in phosphate buffer. Cobalt and copper oxides have shown more important contribution to the observed electroactivity and their presence as impurities in CNT should be taken into account in the evaluation of their electrochemical response. However, it has been confirmed that the presence of a high density of edge plane sites and oxygenated species in CNT are responsible for their electroactivity toward hydrazine when the amount of metallic impurities is relatively low.

전자빔용해법(溶解法)에 의한 탄탈럼 스크랩의 재활용(再活用) 및 정련(精鍊)

The refining effect of tantalum by electron beam melting(EBM) process for recycling tantalum scraps was investigated in the study. The purity of the tantalum metals refined by EBM was evaluated using glow discharge mass spectrometry (GDMS). From the result of GDMS, most impurities in the tantalum metals were removed by EBM down to a few mass ppm levels. The purity of the refined tantalum scraps was improved up to 5N (99.9991%) from 4 N (99.996%) of the initial tantalum scraps. The amount of metallic impurities in the tantalum was decreased from 30 ppm to 8 ppm. In addition, the gaseous impurities in the tantalum were decreased from 470 ppm to 50 ppm. Therefore a possibility of refining method for recycling tantalum scraps by EBM process was confirmed in this study.

Optimized CVD Production of CNT-Based Nanohybrids by Taguchi Robust Design

Taguchi's robust design method is for the first time employed to optimize many aspects of the production of nanohybrids based on C nanotubes by iron-catalyzed chemical vapor deposition in i-C4H10 + H2 atmosphere. By analyzing the outcomes of the catalytic process in terms of selectivity, carbon yield, purity and crystalline arrangement of the hybrid-forming nanotubes, the influence is ranked of the following parameters: synthesis temperature (500-700 degrees C), support material (alumina, magnesia or sodium-exchanged montmorillonite), calcination- (450-750 degrees C) and reduction-(500-700 degrees C) temperatures of the 15 wt% Fe-catalyst. In the experiments initially performed for this purpose, the growth process had, on average, scarce selectivity (2 in a scale 1-5) and poor yield (130 wt%); carbonaceous deposits exhibited unsatisfactory graphitization degree (Raman D/G intensity ratio > 1.5) and contained large amounts of metal impurities (14 wt%) and amorphous carbon (5 wt%). The indications emerging from Taguchi approach to the process optimization are critically examined. The experimental conditions chosen for carrying out test experiments allow achieving excellent selectivity (5) or large yield (760 wt%), hybrids with well-graphitized nanotubes (D/G intensity ratio < 0.6), nearly free of metallic (0.3 wt%) or amorphous (0.4 wt%) inclusions, with consequent possibility of satisfying the different requisites that the specific application to be addressed may require.

Optimum sintering conditions for optical properties of translucent aluminum nitride ceramics

High translucency is one of the excellent properties of AlN ceramics because of its wide optical band gap energy of 6.2 eV. We have achieved success in producing AlN ceramic tube of 98% total visible light transmittance at 0.6 mm thick tube wall by applying an improved sintering technique. This AlN ceramic was produced by sintering at 1880°C using Ca3Al2O6 as a sintering additive and in reduction atmosphere to remove the sintering additive from the final sintered material. After the sintering, the annealing with Al2O3 was carried out to improve the transmittance of AlN ceramics. The amount of metal impurities and carbon were 27ppm and 100ppm, respectively. It is noteworthy that the amount of oxygen in AlN ceramics after the annealing was 0.36wt% which was higher than the 0.07wt% of the as-sintered AlN ceramics. Therefore, total transmittance was improved by the oxygen doping. On the other hand, thermal conductivity of AlN after the annealing was lowered by 35% compared with that of as-sintered AlN. Positron Annihilation Lifetime (PAL) measurement was applied to investigation of a relationship between the total transmittance and lattice defects. The present PAL results confirms the presence of negatively charged atomic-size vacancies that is aluminum site vacancies and also suggests the increase in the concentration of the vacancies after the annealing compared with that of the as-sintered material. However, it can be concluded that there is no relation between aluminum site vacancies and the light transmittance of AlN ceramics.

What amount of metallic impurities in carbon nanotubes is small enough not to dominate their redox properties?

As carbon nanotubes become a part of everyday life, the paramount questions about their toxicity persist. While it has been proven that a significant part of the toxicity of carbon nanotubes is due to the redox activity of the residual metallic impurities present within them, there is still no response to the fundamental question of where the borderline is that would render the impurities 'redox invisible'. Herein we investigate the electrochemical response of carbon nanotubes containing different amounts of impurities towards the reduction of an important biomarker, hydrogen peroxide, and the oxidation of an important impurity marker, hydrazine. We found that the borderline between being redox active/inactive for iron-based impurities lies in the middle-ppm range.

Purging Metal Impurities from Nuclear Fuel using Centrifuge Cascades with Additional Feed Component

Nuclear fuel can be purged, that is metal impurities can be extracted from the uranium hexafluoride, by feeding an additional component, a kind of Freon, C6F12, which is chemically stable with respect to uranium hexafluoride, into the centrifuge purge cascade. The metal impurities are then continuously withdrawn from the purge cascade as a result of the additional feed. Centrifuges can not be easily used for the purge process without the Freon because the amount of metal impurities in the nuclear fuel is usually very small, thus the flow of impurities withdrawn from the product end of the purge cascade needs to be periodically closed down to minimize the loss of uranium hexafluoride. This results in the accumulation of light impurities such as air and HF in stages near the product end of the purge cascade. These light impurities inside the centrifuges may reduce the working effectiveness of the centrifuges or even put them out of service. The additional Freon eliminates this problem, because the light gas can be extracted from the cascade as soon as it reaches the product end of the cascade. Numerical calculations using a typical metal impurity CrO2F2 illustrate the effect of the additional Freon feed in the purge process.

Electrolyzed Water as an Alternative for Environmentally Benign Semiconductor Cleaning

The present semiconductor cleaning technology is based upon RCA cleaning [W. Kern and D.A. Puotinen, Cleaning Solutions Based on Hydrogen Peroxide for use in Silicon Semiconductor Technology (RCA Rev., 1970) pp. 187–206], a high-temperature process that consumes vast amounts of chemicals and ultrapure water (UPW) [T. Futatsuki, T. Imaoka, Y. Yamashita, and K. Mitsumori, J. Electrochem. Soc., 142, 966 (1995)]. Therefore, this technology gives rise to many environmental issues, and some alternatives such as electrolyzed water (EW) are being studied. In this work, intentionally contaminated Si wafers were cleaned using electrolyzed water. The electrolyzed water was generated by an electrolysis system that consists of anode, cathode, and middle chambers. Oxidative water and reductive water were obtained in the anode and cathode chambers, respectively. When a NH4Cl electrolyte was supplied in the middle chamber, the oxidation–reduction potential and pH for anode water (AW) and cathode water (CW) were +1050 mV and 4.8, and −750 mV and 10.0, respectively. AW and CW deterioriated after electrolysis but maintained their characteristics for more than 40 min, which was sufficient for cleaning. Their deterioration was correlated with CO2 concentration changes dissolved from air. Contact angles of UPW, AW, and CW on DHF-treated Si wafer surfaces were 65.9°, 66.5°, and 56.8°, respectively, which characterizes clearly the electrolyzed water. To analyze the amount of metallic impurities on Si wafer surface, inductively coupled plasma, mass spectroscopy was introduced. AW was effective for Cu removal, while CW was more effective for Fe removal. To analyze the number of particles on Si wafer surfaces, we used the particle measurement Tencor 6220. The particle distributions after various particle removal processes maintained the same pattern. Overflow of EW during cleaning particles resulted in the same cleanness as that obtained with the RCA cleaning process. The roughness of patterned wafer surfaces after EW cleaning was similar to that of as-received wafers. Regardless of process sequence in this work, RCA consumed about 9 l of chemicals, while EW consumed only 400 ml HCl electrolyte or 600 ml NH4Cl electrolyte to clean 8-in. wafers. It was thus concluded that EW cleaning technology would be very effective for releasing environmental safety, and health issues in the next generation of semiconductor manufacturing.

Kinetic Model of Metallofullerene Formation in Contact Arc Generator

A kinetic model of the metallofullerene growth process in a contact are generator is developed. the metals chosen for the kinetic analysis were lanthan and calcium. An optimum starting composition of composite electrode was found. In addition, it was discovered that small amounts of metal impurities reduced the fullerene yield just slightly.

Sputter induced resonant ionization spectroscopy for trace analysis in silicon

A resonant ionization mass spectrometer has been developed for the detection of trace amounts of metallic impurities in semiconductor materials. This instrument is essentially a quadrupole SIMS in which the sputtered neutrals are positionized with a laser beam. The wavelength at which various metals can be resonantly photoionized have been determined and the saturation of the ionization as a function of the laser power has been investigated. Calibration plots measured with standards indicate that the detection limit of the instrument is about 0.2 ppm.

Optimum Chromatographic Condition for 2,6-di-t-Butyl-4-pyrazinylaminophenol on RP-HPLC: Metal Influence on Its Elution Profile

Abstract The optimization of chromatographic conditions for the determination of 2,6-di-t-butyl-U-pyrazinyl-aminophenol(DBAP) on reversed-phase HPLC with an aqueous-organic mobile phase were investigated. Undesirable peak shape, of which the quinone form(QF) was produced by the decomposition of DBAP in a stainless steel column, was observed on both of RPC packings containing small and large amounts of metal impurities. Although this conversion reaction was suppressed by washing the ODS gels with a 1 mM EDTA solution, the decomposition of DBAP in the column was still taking place. Concluding that the contamination of metal impurities on the column packing occurs continueously. The use of inert columns such as peek (polyether-ether-ketone), glass-lining columns but except a titan column, packed a high purity RPC packing material which was washed with the EDTA solution prior to use, led to the quantitative result of DBAP in the inert chromatographic system.

Performance of polymer-coated silica C 18 packing materials prepared from high-purity silica gel : The suppression of undesirable secondary retention processes

Coating with silicone polymer of silica surfaces was shown to be very effective in suppressing the undesirable peak tailing in reversed-phase liquid chromatography caused by hydrogen bonding, ion-exchange and chelate formation processes. Silica particles containing various amounts of metal impurities were derivatized to octadecylsilylated (ODS) silica phases with or without subsequent trimethylsilylation, and to a polymer-coated phase with subsequent introduction of octadecyl groups. The performance of endcapped ODS phases prepared from high-purity silica gel was satisfactory for hydrogen-bond acceptors and protonated amines, but not acceptable for chelating compounds. The extent of tailing seen with chelating compounds depends on the solute structure and the metal content of silica particles. Coating with silicone polymer was more effective than trimethylsilylation of ODS phases for the suppression of tailing for chelating compounds, and afforded alkyl-bonded silica packing materials free from undesirable secondary effects by using metal-free silica particles.

In-situ surface probe analysis for impurity flux in the heliotron-E device

The impurity problem is one of the most important areas of study for improving Heliotron-E currentless plasmas. Impurity reduction by 2.45 GHz ECH discharge cleaning and the impurity flux in the edge region of the NBI currentless plasmas were studied by using a newly installed surface analysis station with an “in-situ” AES system. It was confirmed that the light impurities such as C and O were well reduced by the discharge cleaning. The amount of metal impurities on the α-Si probe surface exposed to the plasma increased as the NBI power increased. The impurity level observed in one side of the probe inserted into the edge region of the NBI plasma was larger than that in the opposite side.

Assessment of Metallic Trace Contaminants on Silicon Wafer Surfaces

ABSTRACTNeutron activation, atomic absorption, and voltammetric techniques are presented as appropriate analytical tools to monitor trace amounts of metallic impurities on large diameter silicon wafers. Detection limits and results are compared for standard wafers implanted with Fe, Cu, and Ni. DLTS measurements are included for implanted and as-grown doped wafers.