Distribution by Scientific Domains
Distribution within Physics and Astronomy

Kinds of Impurities

  • donor impurity
  • drug impurity
  • hydrogenic impurity
  • magnetic impurity
  • oxygen impurity
  • potential impurity
  • relate impurity
  • residual impurity
  • unknown impurity

  • Terms modified by Impurities

  • impurity atom
  • impurity center
  • impurity concentration
  • impurity content
  • impurity ion
  • impurity level
  • impurity phase

  • Selected Abstracts

    Simulating the Role of Intrinsic Carbon Impurities in the Divertor Detachment of ASDEX Upgrade

    M. Wischmeier
    Abstract As part of a general effort in validating SOL fluid Monte Carlo codes, well diagnosed ohmic discharges have been done in ASDEX Upgrade reaching from the lowest accessible density up to densities at which both targets were at least partially detached. The numerical code B2.5-EIRENE has been used to simulate these experiments with a particular focus on detachment. Whilst it is possible to qualitatively reproduce the general experimental observations when transiting from attached to detached plasmas, the simulations do not reproduce the detachment threshold observed in experiment quantitatively. The strong asymmetry of the ion flux density between the inner and the outer target with increasing density and in particular the vanishing ion flux, defined as full detachment, at the inner target cannot be reproduced. The influence of various parameters such as chemical sputtering yields and the effect of the activation of drift terms on the results is analyzed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Impurities,The hidden danger in anticonvulsant drugs

    EPILEPSIA, Issue 1 2008
    Thomas Peter Sabroe
    No abstract is available for this article. [source]

    Effect of N Fertilization Rate on Sugar Yield and Non-Sugar Impurities of Sugar Beets (Beta vulgaris) Grown Under Mediterranean Conditions

    J. T. Tsialtas
    Abstract For three successive growing seasons (1999,2001), a completely randomized block design experiment was established at the surrounding area of each of four sugar beet processing plants of Hellenic Sugar Industry SA, Greece (a total of 12 experiments). Nitrogen was applied at five rates (0, 60, 120, 180 and 240 kg N ha,1) and six replications per rate. Nitrogen fertilization had site-specific effects on quantitative (fresh root and sugar yields) and qualitative (sucrose content, K, Na, , -amino N) traits. When data were combined over years and sites, fresh root and sugar yields were maximized at high N rates (330.75 and 295 kg N ha,1 respectively), as derived from quadratic functions fitted to data. In three trials, increased N rates had negative effects on root and sugar yield. These sites were characterized by high yield in control plots, light soil texture (sand > 50 %) and low CEC values. When data were converted into relative values (the ratio of the trait values to the control mean of each experiment), root and sugar yield was found to be maximized at higher N rates (350 and 316 kg N ha,1, respectively). Sucrose content was strongly and linearly reduced by the increased N rates when data were combined but a significant reduction with increasing N rates was found in only two sites. Non-sugar impurities (K, Na, , -amino N) were positively related to the increased N rates when data were combined. Sodium and , -amino N showed to be most affected by N fertilization as positive relationships were found in six and eight of 12 locations, respectively. Increased N supply resulted in higher soil NO3 -N concentrations (0,90 cm depth) at harvest which were related with amino N contents in sugar beet roots (in 1999 and 2001). [source]

    Impurities in a morphine sulfate drug product identified as 5-(hydroxymethyl)-2-furfural, 10-hydroxymorphine and 10-oxomorphine

    Seán S. Kelly
    Abstract Stability testing of morphine sulfate formulated with nonpareil sugar seeds (consisting of sucrose and starch) and fumaric acid revealed the formation of the three impurities 5-(hydroxymethyl)-2-furfural, 10-hydroxymorphine and 10-oxomorphine. 5-(Hydroxymethyl)-2-furfural was isolated via semipreparative HPLC utilizing volatile mobile phase constituents and was identified by analysis of its HRMS and NMR spectra. 10-Hydroxymorphine and 10-oxomorphine were obtained via semipreparative HPLC and subsequent removal of ion-pair reagents using an anion exchange resin, or by solid phase extraction, and identified by spectroscopic analysis followed by comparison with authentic materials. 5-(Hydroxymethyl)-2-furfural is a degradation product of hexose sugars, and its formation in the presence of morphine sulfate formulated with fumaric acid suggests that caution should be exercised when including nonpareil seeds in formulations that contain acidic drug salts and/or acid excipients. The preliminary results of tests on the interaction of acidic salts of some other drugs with nonpareil seeds are presented. © 2003 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 92:485,493, 2003 [source]

    Effect of Segregating Impurities on the Grain-Boundary Character Distribution of Magnesium Oxide

    Francine Papillon
    The grain-boundary character distribution (GBCD) of undoped MgO has been measured and compared with samples containing small concentrations of Ca, Sr, Ba, and Y. Auger electron spectroscopy measurements of intergranular fracture surfaces verified that Ca, Ba, and Y segregated anisotropically to grain boundaries (GBs). The segregation of Sr was not detected. The GBCDs of Ca, Ba, and Y doped MgO have more GBs comprised of {100} planes than the undoped material and the fractional area of these planes was highest in the Ca-containing samples. Sr impurities, on the other hand, have no measurable influence on the GBCD. The results demonstrate that GB plane distributions can be controlled through impurity additions. [source]

    Influence of Impurities on Dispersion Properties of Bayer Alumina

    J. Kiennemann
    Among the different impurities contained in Bayer alumina (Ca, Fe, Na, Si, Mg), calcium was found to greatly influence the dispersion of alumina particles in water. Up to 90% of calcium is dissolved at acidic pH, whereas calcium remains on the alumina surface in the basic pH range and screens the negative Al,O, charges. The presence of calcium, through reducing repulsive interactions between particles, has a negative effect on the dispersion of alumina. The adsorption of the Na+ salt of poly(acrylic acid) (PAA-Na) is strongly influenced by Ca2+/PAA-Na interactions in suspension with an increase of the maximum adsorbed amount of PAA-Na in the presence of calcium. The amount of PAA-Na needed to reach a high electrostatic repulsion and a minimum of viscosity is 2 times higher in the presence of 400 pm calcium than for a low calcium content (,80 ppm). Finally, with an appropriate amount of PAA-Na, a similar state of dispersion can be reached with or without the presence of calcium. [source]

    Fabrication of Arsenic Selenide Optical Fiber with Low Hydrogen Impurities

    Vinh Q. Nguyen
    Arsenic selenide glass optical fibers typically possess extrinsic absorption bands in the infrared wavelength region associated with residual hydrogen and oxygen related impurities, despite using purified precursors. We report a purification process based on the addition of 0.1 wt% tellurium tetrachloride (TeCl4) to the glass. During melting, the chlorine from TeCl4 reacts with the hydrogen impurities to produce volatile products (e.g., HCl) that can be removed by subsequent dynamic distillation. The processing conditions have been modified accordingly to give very low H,Se impurity content. Consequently, the H,Se absorption band centered at 4.57 ,m has been reduced from tens of dB/m to 0.2 dB/m. [source]

    Fabrication of Arsenic Sulfide Optical Fiber with Low Hydrogen Impurities

    Vinh Q. Nguyen
    Arsenic sulfide glass optical fibers typically possess extrinsic absorption bands in the infrared wavelength region associated with residual hydrogen and oxygen related impurities, despite using purified precursors. We report a purification process based on the addition of tellurium tetrachloride (TeCl4) to the glass. During melting, the chlorine from TeCl4 reacts with the hydrogen impurities to produce volatile products (e.g., HCl) that can be removed by subsequent dynamic distillation. The processing conditions have been modified accordingly to produce optical fibers with significantly reduced loss due to hydrogen sulfide impurity content (1.5 dB/m). [source]

    Identification and Determination of Impurities, Edited by S. GÖRÖG.

    $288.00, Elsevier Science, Eur 249.58.
    No abstract is available for this article. [source]

    Impurities , the hidden danger in anticonvulsant drugs

    T. P. Sabroe
    No abstract is available for this article. [source]

    Accumulation Process of High-Z Impurity in Toroidal Rotating Tokamak Plasma

    K. Hoshino
    Abstract The accumulation process of high-Z impurity in toroidal rotating tokamak plasma is investigated. A new inward pinch of high-Z impurity due to the ionization/recombination processes is derived using an analytic model. This inward pinch is driven by the large deviation of a drift orbit from a magnetic surface and the resultant variation of the charge state along the drift orbit. The pinch velocity increases with increasing toroidal rotation speed in both the co-direction and the ctr-direction. The inward pinch expected by the analytic model is really observed in the numerical simulation using the IMPGYRO code (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Low temperature structural transformations of dilute KTa1,xNbxO3: x = 0.018, quantum superparaelectric or reentrant glass scenario?

    V. A. Trepakov
    Abstract Impurity induced structural transformations are studied for KTa1,xNbxO3 with x = 0.0018 (KTN-1.8) by low-frequency linear and non-linear dielectric spectroscopy techniques. Nb admixture leads to the appearance of a sharp ,,(T) maximum accompanying the ferroelectric phase transition at TC , 27 K, and a glass-like state formation at lower temperatures. The linear permittivity evidences properties inherent to systems being near the quantum-mechanical displacive limit and shows the long range polar order with macroscopic polarization formation at ,27 K. This conclusion was proven by nonlinear polarization response stuidy under dc electric field action, which evidenced also the proximity of the three-critical point. Above 27 K, the nonlinearity increases at cooling in accordance with the Devonshire theory for the paraelectric phase of conventional ferroelectrics. Below 27 K, the random distribution of Nb5+ ions and related system's inhomogeneities provoke a new low temperature phase state formation, which can be treated as reentrant polar-glass. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Free-Standing HVPE-GaN Quasi-Substrates: Impurity and Strain Distributions

    T. Paskova
    Abstract We report a study of the physical properties of free-standing HVPE-GaN quasi-substrates. A variety of characterization techniques was employed in order to characterise in a comparative way the two sides of the films. The as-grown Ga-face was found to have lower density of both, structural and impurity defects. This leads to a lower concentration of free carriers and residual strain in the Ga-face compared to that in the N-face. The optical properties were found to be strongly influenced by the specific defect structure in both faces. [source]

    Multi-Fluid Modeling of Low-Recycling Divertor Regimes

    R. D. Smirnov
    Abstract The low-recycling regimes of divertor operation in a single-null NSTX magnetic configuration are studied using computer simulations with the edge plasma transport code UEDGE. The edge plasma transport properties pertinent to the low-recycling regimes are demonstrated. These include the flux-limited character of the parallel heat transport and the high plasma temperatures with the flattened profiles in the scrape-off-layer. It is shown that to maintain the balance of particle fluxes at the core interface the deuterium gas puffing rate should increase as the divertor recycling coefficient decreases. The radial profiles of the heat load to the outer divertor plate, the upstream radial plasma profiles, and the effects of the cross-field plasma transport in the low-recycling regimes are discussed. It is also shown that recycling of lithium impurities evaporating from the divertor plate at high surface temperatures can reverse the low-recycling divertor operational regime to the high-recycling one and may cause thermal instability of the divertor plate (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Stabilization of Radiation-Condensation Instability by Light Impurity Injection

    A. A. Pshenov
    Abstract As it has been shown in [1,2], Radiation-Condensation Instability (RCI) may initiate Microfaceted Asymmetric Radiation from the Edge (MARFE) in tokamaks (see also review papers [3-5]). Nevertheless, experiments demonstrate the stable regimes with strongly radiated edge plasmas after Ne injection [6-8] or in siliconized discharges. Two effects destabilize radiative plasmas, the decrease of radiation losses Q with the electron temperature Te increase, and the increase of Q with electron and impurity densities rise. The finite relaxation time of impurity distribution over ionization states [6] as well as the thermal force acting on the growth rate doesn't shift the instability margin. Hence, one can examine the stability margin using the approximation of the coronal equilibrium. Radiation losses of intrinsic impurities like beryllium, carbon and nitrogen usually decrease with the temperature increase at the temperature range typical for the edge (see Fig. 1, curve 1). The situation may be significantly different for impurity mixtures. Radiation losses L , Q /(nenI)normalized by electron and impurity densities ne and nI for the mixture of carbon and neon are shown in Fig. 1, curves 2-5. One can see that ,Q/,T > 0 for practically any temperature at the edge if the concentration ratio nNe/nC , 5. Hence, one can expect the stabilization of RCI by injection of additional impurity and achievement of stable regime with the strongly radiated edge plasmas. The stability of plasmas with few impurity mixtures is examined in the present paper numerically (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Reduced Models of Impurity Seeded Edge Plasmas

    D. Kh.
    Abstract The reduced descriptions of the distribution of impurities over ionization states, radiation losses and plasma dynamics are reviewed. Two and three most important ion approximation for light impurities and continuous descriptions of heavy impurities are discussed. Reduced descriptions of atomic processes like ionization, photo- and dielectronic recombination rates as well as of radiation abilities are proposed. As it shown, thermal forces, final relaxation times of impurity distributions over ionization states, charge-exchange and opacity effects must be taken into account in reduced models, especially for ITER problems. Linear and nonlinear stages of the radiation-condensation mode as well as some aspects of disruptions and noble gas injection into tokamak plasmas are analyzed with the reduced models. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Influence of the Wall Characteristics on the Development of MARFE in Tokamaks

    O. Marchuk
    Abstract Multifaceted asymmetric radiation from the edge (MARFE) normally develops in fusion devices close to the density limit. MARFE is considered a result of thermal instabilities excited under critical conditions through different mechanisms: impurity radiation, recycling of neutral particles, anomalous transport of charged particles and energy. Recent experiments on tokamaks TEXTOR and JET show that plasma-wall interaction, leading to release of recycling neutrals and impurities, plays a very important role for the formation of MARFE. In the present contribution we develop further the MARFE models based on the instability of particle recycling on the tokamak wall by including a simple description for the release of recycling neutrals from the wall surface into the plasma. This development takes into account the time delay between the out flow of charged particles from the plasma and in flux of neutrals. The linear stability analysis shows that this does not change the critical plasma density for the MARFE formation but modifies significantly the growth rate of unstable perturbations developing when the density exceeds the threshold. These findings are confirmed in a non-linear consideration by solving the equations for the particle, momentum and energy transfer in the plasma coupled with the wall particle balance equations. This is done in a one-dimensional approximation by taking into account the variation of the main plasma parameters in the poloidal direction and making averaging in the radial direction over the plasma edge width of the penetration depth of neutrals. The intrinsic poloidal asymmetry of the system, defining the MARFE localization, is introduced by the Shafranov shift of magnetic flux surfaces. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Plasma Edge Physics with B2-Eirene

    R. Schneider
    Abstract The B2-Eirene code package was developed to give better insight into the physics in the scrape-off layer (SOL), which is defined as the region of open field-lines intersecting walls. The SOL is characterised by the competition of parallel and perpendicular transport defining by this a 2D system. The description of the plasma-wall interaction due to the existence of walls and atomic processes are necessary ingredients for an understanding of the scrape-off layer. This paper concentrates on understanding the basic physics by combining the results of the code with experiments and analytical models or estimates. This work will mainly focus on divertor tokamaks, but most of the arguments and principles can be easily adapted also to other concepts like island divertors in stellarators or limiter devices. The paper presents the basic equations for the plasma transport and the basic models for the neutral transport. This defines the basic ingredients for the SOLPS (Scrape-Off Layer Plasma Simulator) code package. A first level of understanding is approached for pure hydrogenic plasmas based both on simple models and simulations with B2-Eirene neglecting drifts and currents. The influence of neutral transport on the different operation regimes is here the main topic. This will finish with time-dependent phenomena for the pure plasma, so-called Edge Localised Modes (ELMs). Then, the influence of impurities on the SOL plasma is discussed. For the understanding of impurity physics in the SOL one needs a rather complex combination of different aspects. The impurity production process has to be understood, then the effects of impurities in terms of radiation losses have to be included and finally impurity transport is necessary. This will be introduced with rising complexity starting with simple estimates, analysing then the detailed parallel force balance and the flow pattern of impurities. Using this, impurity compression and radiation instabilities will be studied. This part ends, combining all the elements introduced before, with specific, detailed results from different machines. Then, the effect of drifts and currents is introduced and their consequences presented. Finally, some work on deriving scaling laws for the anomalous turbulent transport based on automatic edge transport code fitting procedures will be described. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Stochastic and Relaxation Processes in Argon by Measurements of Dynamic Breakdown Voltages

    V. Lj.
    Abstract Statistically based measurements of breakdown voltages Ub and breakdown delay times td and their variations in transient regimes of establishment and relaxation of discharges are a convenient method to study stochastic processes of electrical breakdown of gases, as well as relaxation kinetics in afterglow. In this paper the measurements and statistical analysis of the dynamic breakdown voltages Ub for linearly rising (ramp) pulses in argon at 1.33 mbar and the rates of voltage rise k up to 800 V s,1 are presented. It was found that electrical breakdowns by linearly rising (ramp) pulses is an inhomogeneous Poisson process caused by primary and secondary ionization coefficients , , , and electron yield Y variations on the voltage (time). The experimental breakdown voltage distributions were fitted by theoretical distributions by applying approximate analytical and numerical models. The afterglow kinetics in argon was studied based on the dependence of the initial electron yield on the relaxation time Y0 (, ) derived from fitting of distributions. The space charge decay was explained by the surface recombination of nitrogen atoms present as impurities. The afterglow kinetics and the surface recombination coefficients on the gas tube and cathode were determined from a gas-phase model. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Blob Transport in the Tokamak Scrape-off-Layer

    D. A. D'Ippolito
    Abstract Recent experimental evidence suggests the importance of fast radial plasma transport in the scrape-off-layer (SOL) of tokamaks. The outward transport appears to be convective rather than diffusive, extends into the far SOL, and can produce significant recycling from the main-chamber walls, partially bypassing the divertor. A plausible theoretical mechanism to explain this phenomenon is the radial transport of "blobs" of locally dense plasma created by turbulent processes. A related process is the inward transport of "holes" of reduced density plasma, which provides a mechanism for rapid inward transport of impurities. The blob model is also consistent with the spatial and temporal intermittency and the non-Gaussian statistics observed in the SOL plasma. This paper reviews the present status of blob theory, including analytic models and simulations, and discusses the preliminary comparisons of the blob model with experimental data. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    In situ measurement of growth kinetics of {100} KDP crystal faces in the presence of polyphosphate impurities

    Bing Liu
    Abstract The face growth rate and critical supersaturation of {100} face were in situ measured using the laser-polarization-interference technique in the presence of potassium pyrophosphate, trimetric sodium phosphate and sodium hexametaphosphate impurities. The polyphosphate impurities inhibit the growth rate of prismatic faces. The face growth rate as a function of supersaturation at different impurity concentrations, as well as critical supersaturation as a function of impurity concentrations, was found in good agreement with a two-dimensional nucleation model in the pure system and Kubota and Mullin's model in the presence of impurities. The average distance L between active sites available for impurity adsorption as well as the edge free energy was calculated. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    In situ study of growth and dissolution kinetics of ammonium oxalate monohydrate single crystals from aqueous solutions containing cationic impurities

    K. Sangwal
    Abstract The results of an in situ investigation of the effect of four different bi- and trivalent cations (Fe(III), Cu(II), Mn(II) and Cr(III)) on the displacement velocity of individual growth steps on the (110) face of ammonium oxalate monohydrate crystals as a function of supersaturation are described and discussed. It was observed that: (1) at a particular temperature of pure solutions and solutions containing impurities, the velocity v of movement of the [110] growth steps is always greater than that of the [111] steps, (2) fluctuations in the velocity of individual growth steps occur in all solutions containing similar concentrations of different impurities, (3) the value of kinetic coefficient , for growth steps decreases with an increase in the concentration ci of Cu(II) impurity, but that for dissolution steps does not depend on ci; moreover, the value of kinetic coefficient , for growth steps is higher than that of dissolution steps, and (4) in the presence of Mn(II) and Cr(III) impurities, the kinetic coefficient , for dissolution steps is several times greater than that for growth steps. The results are explained from the standpoint of Kubota-Mullin model of adsorption of impurities at kinks in the steps and the stability of dominating complexes present in solutions. Analysis of the results revealed that: (1) the effectiveness of different impurities in inhibiting growth increases in the order: Fe(III), Cu(II), Mn(II), and Cr(III), and this behavior is directly connected with the stability and chemical constitution of dominating complexes in saturated solutions, (2) fluctuations in the velocity of growth steps is associated with the effectiveness of an impurity for adsorption; the stronger the adsorption of an impurity, the higher is the fluctuation in step velocity v, and (3) depending on the nature of the impurity, the kinetic coefficient for the dissolution steps can remain unchanged or can be higher than that of the growth steps. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Silicon crystal growth from the melt: Analysis from atomic and macro scales

    K. Kakimoto
    Abstract The effect of impurity concentration on thermal conductivity of natural and isotope silicon by using equilibrium molecular dynamics simulation is investigated. It was found that the concentrations of the impurities such as boron, phosphor and arsene play an important role in the propagation of phonons in silicon crystals. It was also clarified that a mass difference of impurities and host crystals results in degradation of thermal conductivity of silicon. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Influence of complex formation upon inclusion of Mn(II), Co(II), Ni(II), and Cu(II) in ZnC2O4·2H2O

    B. Donkova
    Abstract The inclusion of 3d-impurities Mn(II), Co(II), Ni(II) and Cu(II) in a crystalline precipitate of ZnC2O4·2H2O is investigated. This study is a part of the systematic one deal with the mechanism of inclusion of 3d-ions in sparingly soluble oxalate systems. The experiments are carried out in bi- end multi-component systems at two different mediums , one with deficiency of oxalate ions, another with excess. The insertion of 3d-ions upon mass crystallization of ZnC2O4·2H2O does not proceed by a simple ionic substitution. The results show that the inserted amount of impurity depends on some physicochemical characteristics of the neutral monooxalato complexes [MnC2O4]o, [CoC2O4]o, [NiC2O4]o and [CuC2O4]o. Good agreement between included impurity and the concentration of its complex in the solution is established. The stability constant of monooxalato complex affects the impurity inclusion. This effect depends on the medium nature. In the deficiency of oxalate ions the factor determining the inclusion is thermodynamic one , stability of monooxalato complexes. In the excess of oxalate ions inserted amount depends on kinetic factor , the formation rate of these complexes. In the term of that the insertion of Mn(II) is definitely different in the two mediums while that of the Ni (II) does not depend on the medium. The copper shows deviation from overall dependence in the two mediums due to the Jahn-Teller distortion. Its double decreasing insertion in the excess of oxalate ions is related with stabilization of [Cu(C2O4)2]2- . The conclusions presume that by varying the background medium and taking in view the ions present in the solution, the amount of inserted impurities can be predicted and controlled. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    An improved validated ultra high pressure liquid chromatography method for separation of tacrolimus impurities and its tautomers

    Acharya Subasranjan
    Abstract A selective, specific and sensitive ultra high pressure liquid chromatography (UHPLC) method was developed for determination of tacrolimus degradation products and tautomers in the preparation of pharmaceuticals. The chromatographic separation was performed on Waters ACQUITY UPLC system and BEH C8 column using gradient elution of mobile phase A (90:10 v/v of 0.1% v/v triflouroacetic acid solution and Acetonitrile) and mobile phase B (90:10 v/v acetonitrile and water) at a flow rate of 0.6 mL min,1. Ultraviolet detection was performed at 210 nm. Tacrolimus, tautomers and impurities were chromatographed with a total run time of 25 min. Calibration showed that the response of impurity was a linear function of concentration over the range 0.3,6 µg mL,1 (r2 , 0.999) and the method was validated over this range for precision, intermediate precision, accuracy, linearity and specificity. For precision study, percentage relative standard deviation of each impurity was < 15% (n = 6). The method was found to be precise, accurate, linear and specific. The proposed method was successfully employed for estimation of tacrolimus impurities in pharmaceutical preparations. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Dual CD system-modified MEEKC method for the determination of clemastine and its impurities

    ELECTROPHORESIS, Issue 19 2010
    Serena Orlandini
    Abstract A dual system of CDs was used for the first time in MEEKC with the aim of determining clemastine and its three main related impurities in both drug substances and tablets. The addition of methyl-,-cyclodextrin and heptakis(2,6-di- O -methyl)-,-cyclodextrin to the microemulsion pseudo-stationary phase was essential to increase the resolving power of the system to obtain a baseline separation among the compounds. The best microemulsion composition was identified by mixture design and the effects of the factors concentrations of CDs and voltage were investigated by a response surface study applying a Central Composite Design. In both cases, Derringer's desirability function made it possible to find the global optimum, which corresponded to the following combination: microemulsion, 89.8% 10,mM borate buffer pH 9.2, 1.5% n -heptane and 8.7% of SDS/n -butanol in 1:2 ratio; 18,mM methyl-,-cyclodextrin, 38,mM heptakis(2,6-di- O -methyl)-,-cyclodextrin, 17,kV. By applying these conditions, the separation was completed in about 5.5,min. The method was validated following International Conference on Harmonisation guidelines and was applied to a real sample of clemastine tablets. [source]

    Recombinant clotting factor VIII concentrates: Heterogeneity and high-purity evaluation

    ELECTROPHORESIS, Issue 16 2010
    Gian Maria D'Amici
    Abstract Factor VIII is an important glycoprotein involved in hemostasis. Insertion of expression vectors containing either the full-length cDNA sequence of human factor VIII (FLrFVIII) or B-domain deleted (BDDrFVIII) into mammalian cell lines results in the production of recombinant factor VIII (rFVIII) for therapeutic usage. Three commercially available rFVIII concentrates (Advate®, Helixate NexGen® and Refacto®), either FLrFVIII or BDDrFVIII, were investigated by 1- and 2-DE and MS. The objective of this study was to compare the heterogeneity and the high purity of both rFVIII preparations before and after thrombin digestion. In particular, the 2-D gel was optimized to better highlight the presence of contaminants and many unexpected proteins. Recombinant strategies consisting of insertion of expression vectors containing BDDrFVIII and FLrFVIII resulted in homogeneous and heterogeneous protein products, respectively, the latter consisting in a heterogeneous mixture of various B-domain-truncated forms of the molecule. Thrombin digestion of all the three rFVIII gave similar final products, plus one unexpected fragment of A2 domain missing 11 amino acids. Regarding the contaminants, Helixate NexGen® showed the presence of impurities, such as Hsp70,kDa, haptoglobin and proapolipoprotein; Refacto® showed glutathione S -transferase and ,-lactamase, whereas Advate® apparently did not contain any contaminants. The proteomic approach will contribute to improving the quality assurance and manufacturing processes of rFVIII concentrates. In this view, the 2-DE is mandatory for revealing the presence of contaminants. [source]

    CE assay for simultaneous determination of charged and neutral impurities in dexamphetamine sulfate using a dual CD system

    ELECTROPHORESIS, Issue 9 2010
    Sudaporn Wongwan
    Abstract A CE assay for the simultaneous determination of charged and uncharged potential impurities (1S,2S -(+)-norpseudoephedrine, 1R,2S -(,)-norephedrine, phenylacetone and phenylacetone oxime) of dexamphetamine sulfate including the stereoisomer levoamphetamine was developed and validated. The optimized background electrolyte consisted of a 50,mM sodium phosphate buffer, pH 3.0, containing 80,mg/mL sulfobutylether-,-CD and 25,mg/mL sulfated ,-CD. Separations were performed in 40.2/35,cm, 50 ,m id fused-silica capillaries at a temperature of 20°C and an applied voltage of ,10,kV. 1R,2S -(,)-ephedrine was used as internal standard. The assay was validated in the range of 0.05,1.0% for the related substances and in the range of 0.05,5.0% for levoamphetamine. The LOD was 0.01,0.02% depending on the analyte. The assay also allowed the separation of the E,Z-stereoisomers of phenylacetone oxime. The effect of the degree of substitution of sulfobutylether-,-CD was investigated. In commercial samples of dexamphetamine sulfate between 3.2 and 3.7% of levoamphetamine were found. Furthermore, phenylacetone and phenylacetone oxime could be observed at the LOD, indicating the synthetic origin of the investigated samples. [source]

    Testing of the influenza virus purification by CIEF

    ELECTROPHORESIS, Issue 2 2010
    Marie Horká
    Abstract In virological practice, the pre-concentration, purification and subsequent determination of the purity and concentration of the viruses from the cultural medium and/or from the real sample are required. The conventional techniques used today are equipment demanding, time-consuming and laborious. In this study, the CIEF of influenza viruses with UV detection has been developed and subsequently used to test the purification of the virus from the biological samples. The equine and swine influenza viruses present in infected allantoic fluid of specific pathogen free embryonated chicken eggs were precipitated by using PEG 6000 and sodium chloride. The precipitated viruses were centrifuged at 14,000×g, and the impurities of different densities were removed by using the sucrose gradients. The efficiency of the virus purification technique was examined by the CIEF and compared to the results of real-time PCR. The pIs of both influenza viruses were determined. Simultaneously, the CIEF was found to be a suitable method for the rapid testing of the efficiency of the virus purification. [source]

    A new evaluation technique for the detection of impurities in purified proteins via CE with native UV-LIF

    ELECTROPHORESIS, Issue 2 2010
    Audrey Rodat
    Abstract An analytical methodology for quality control analyses of IgG and their impurities is presented using a new UV-LIF (266,nm) detector inside the cassette of a CE instrument and its performance was evaluated. The observed sensitivity was very close to that obtained by silver staining of slab gels (LOD of 25,ng/mL), while the sensitivity of the analysis is 80 times better than with CE/UV absorption (214,nm). Examples of the analysis of pharmaceutical and other commercial IgGs are provided and the kinetics of the reduction of IgG by ,-mercaptoethanol is reported, demonstrating the ease of performing the analysis. [source]