scholarly journals The Risk of Recrystallization: Changes to the Toxicity and Morphology of Pyrimethamine

2014 ◽  
Vol 17 (2) ◽  
pp. 190 ◽  
Author(s):  
Zak Perold ◽  
Mino R Caira ◽  
Marius Brits
Keyword(s):  
Solid State ◽  
Angle Of Repose ◽  
Powder Flow ◽  
Solid State Chemistry ◽  
X Ray Diffraction ◽  
Thermal Methods ◽  
X Ray ◽  
Infra Red ◽  
Computational Work ◽  
Tapped Density

PURPOSE. Pyrimethamine, an anti-malarial agent known to exhibit solid state polymorphism, may be purified by means of recrystallization. Recrystallization may alter the solid state chemistry of pharmaceuticals, which may impact the toxicity and/or manufacturability thereof. We evaluated the risks associated with the recrystallization of pyrimethamine. METHODS. Pyrimethamine was recrystallized using several organic solvents. X-ray diffraction, thermal analysis, infra-red spectroscopy, microscopy, flowability -, solubility and dissolution testing as well as computational work were employed to evaluate the recrystallized products. RESULTS. A toxic solvatomorph of pyrimethamine (Pyr-MeOH) was found to be the product from methanol recrystallization. The elucidation of – and the elaboration on the unique characteristics of Pyr-MeOH provides the pharmaceutical industry with several means to identify Pyr-MeOH and to distinguish it from the pharmaceutically preferred anhydrous form (Pyr). Thermal methods of analysis found that the toxicity of Pyr-MeOH may be reversed by overcoming a desolvation activation energy of 148 kJ/mol. In addition it was found that recrystallization altered the morphology of Pyr. Angle of repose and tapped density determinations identified that the different morphologies of Pyr displayed differences in powder flow and compressibility behaviour and In Silico calculations were successful in rendering morphologies resembling that found experimentally. CONCLUSION. We present a solvatomorph of pyrimethamine and provide several characteristic means to identify this unwanted toxic form and quantified the energy required to overcome its toxicity. In addition we describe that Pyr may present in different morphologies and show how it may impact the manufacturability thereof. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

scholarly journals In situ X-ray diffraction computed tomography studies examining the thermal and chemical stabilities of working Ba0.5Sr0.5Co0.8Fe0.2O3−δ membranes during oxidative coupling of methane

2020 ◽  
Vol 22 (34) ◽  
pp. 18964-18975
Author(s):  
Dorota Matras ◽  
Antonis Vamvakeros ◽  
Simon D. M. Jacques ◽  
Vesna Middelkoop ◽  
Gavin Vaughan ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Solid State ◽  
Oxidative Coupling ◽  
Structural Changes ◽  
Oxidative Coupling Of Methane ◽  
Membrane Reactors ◽  
Solid State Chemistry ◽  
X Ray Diffraction ◽  
X Ray

In situ XRD-CT and post-reaction SEM/EDX were used to study the solid-state chemistry and structural changes of Ba0.5Sr0.5Co0.8Fe0.2O3−δ membrane reactors during the oxidative coupling of methane reaction.

scholarly journals Unravelling the spatial dependency of the complex solid-state chemistry of Pb in a paint micro-sample from Rembrandt's Homer using XRD-CT

2019 ◽  
Vol 55 (13) ◽  
pp. 1931-1934 ◽  
Author(s):  
Stephen W. T. Price ◽  
Annelies Van Loon ◽  
Katrien Keune ◽  
Aaron D. Parsons ◽  
Claire Murray ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Solid State ◽  
Solid State Chemistry ◽  
Spatial Dependency ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystalline Surface

X-ray diffraction computed tomography (XRD-CT) has been used to identify the nature of crystalline surface deposits in Rembrandt's Homer.

Structural Studies of Potassium Hexatitanates Prepared under Hydrothermal and Solid State Conditions

2006 ◽  
Vol 517 ◽  
pp. 222-226 ◽  
Author(s):  
Rosiyah Yahya ◽  
A. Hassan ◽  
Z. Aiyub
Keyword(s):  
Electron Microscopy ◽  
Solid State ◽  
Potassium Ions ◽  
Particle Sizes ◽  
Structural Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
Infra Red ◽  
Potassium Hexatitanate ◽  
Scanning Electron

The structural studies of potassium hexatitanates prepared under both hydrothermal and solid state conditions were carried out. Fourier Transform Infra-red spectroscopy (FTIR) results revealed that potassium hexatitanate structure consisted of TiO6 octahedral units irrespective of the preparative conditions and particle size. X-ray diffraction (XRD) results showed that the only potassium hexatitanate phase was detectable and the structure is of the Wadsley-type consisting of chains of Ti-O octahedral sharing edges with tunnels in which the potassium ions are located. From scanning electron microscopy (SEM) results, the different preparative conditions resulted in different particle sizes and morphologies of the potassium hexatitanate formed.

scholarly journals PEMBUATAN DAN KARAKTERISASI KATALIS TIO2/KARBON AKTIF DENGAN METODE SOLID STATE

2015 ◽  
Vol 9 (1) ◽  
pp. 34 ◽  
Author(s):  
Upita Septiani ◽  
Mega Gustiana ◽  
Safni
Keyword(s):  
Solid State ◽  
Wave Number ◽  
Composite Catalyst ◽  
Not Given ◽  
X Ray Diffraction ◽  
Sem Images ◽  
Solid State Method ◽  
X Ray ◽  
Infra Red ◽  
Xrd Patterns

Composite catalyst of TiO2/Activated Carbon (TiO2/AC) had been synthesized with successfully by solid-state method. Synthesis was done by varying the addition of AC 5%, 10% and 15% of the mass of TiO2 was used. Composite catalyst was calcinated at temperature 400°C and characterized by Fourier Transform Infra-Red (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). FTIR spectrum show that the absorption appearedin the regionof C=C at wave number 1600-1800 cm-1, that assumed from AC. From XRD we can see that with variated of AC do not given different XRD patterns significantly, crystal structure of composite catalyst is anatase. SEM images showed that AC prevented the aglomeration of TiO2 that would expand surface area and increased catalytic activity of TiO2.

Electron Microscopy of Human Gallstones

1971 ◽  
Vol 29 ◽  
pp. 296-297
Author(s):  
C. Wolpers ◽  
R. Blaschke
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Bile Pigment ◽  
X Ray Diffraction ◽  
Triclinic Crystal System ◽  
X Ray ◽  
Follow Up Study ◽  
Infra Red ◽  
Main Components

Scanning microscopy was used to study the surface of human gallstones and the surface of fractures. The specimens were obtained by operation, washed with water, dried at room temperature and shadowcasted with carbon and aluminum. Most of the specimens belong to patients from a series of X-ray follow-up study, examined during the last twenty years. So it was possible to evaluate approximately the age of these gallstones and to get information on the intensity of growing and solving.Cholesterol, a group of bile pigment substances and different salts of calcium, are the main components of human gallstones. By X-ray diffraction technique, infra-red spectroscopy and by chemical analysis it was demonstrated that all three components can be found in any gallstone. In the presence of water cholesterol crystallizes in pane-like plates of the triclinic crystal system.

The Collagenic Molecular Structural Unit of Solid State Complexes

1971 ◽  
Vol 29 ◽  
pp. 478-479
Author(s):  
Kenneth M. Richter ◽  
John A. Schilling
Keyword(s):  
Molecular Weight ◽  
Solid State ◽  
Structural Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naoh Treatment

The structural unit of solid state collagen complexes has been reported by Porter and Vanamee via EM and by Cowan, North and Randall via x-ray diffraction to be an ellipsoidal unit of 210-270 A. length by 50-100 A. diameter. It subsequently was independently demonstrated by us in dog tendon, dermis, and induced complexes. Its detailed morphologic, dimensional and molecular weight (MW) aspects have now been determined. It is pear-shaped in long profile with m diameters of 57 and 108 A. and m length of 263 A. (Fig. 1, tendon, KMnO4 fixation, Na-tungstate; Fig. 2a, schematic of unit in long, C, and x-sectional profiles of its thin, xB, and bulbous, xA portions; Fig. 2b, tendon essentially unmodified by ether and 0.4 N NaOH treatment, Na-tungstate). The unit consists of a uniquely coild cable, c, of ṁ 22.9 A. diameter and length of 2580-3316 A. The cable consists of three 2nd-strands, s, each of m 10.6 A.

TEM studies of solid-state reactions in sputter-deposited Nb/Al multilayer thin films

1996 ◽  
Vol 54 ◽  
pp. 1020-1021
Author(s):  
F. Ma ◽  
S. Vivekanand ◽  
K. Barmak ◽  
C. Michaelsen
Keyword(s):  
Thin Films ◽  
Solid State ◽  
Stoichiometric Composition ◽  
Analytical Electron Microscopy ◽  
Grain Structure ◽  
Solid State Reactions ◽  
Multilayer Thin Films ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sputter Deposited

Solid state reactions in sputter-deposited Nb/Al multilayer thin films have been studied by transmission and analytical electron microscopy (TEM/AEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The Nb/Al multilayer thin films for TEM studies were sputter-deposited on (1102)sapphire substrates. The periodicity of the films is in the range 10-500 nm. The overall composition of the films are 1/3, 2/1, and 3/1 Nb/Al, corresponding to the stoichiometric composition of the three intermetallic phases in this system.Figure 1 is a TEM micrograph of an as-deposited film with periodicity A = dA1 + dNb = 72 nm, where d's are layer thicknesses. The polycrystalline nature of the Al and Nb layers with their columnar grain structure is evident in the figure. Both Nb and Al layers exhibit crystallographic texture, with the electron diffraction pattern for this film showing stronger diffraction spots in the direction normal to the multilayer. The X-ray diffraction patterns of all films are dominated by the Al(l 11) and Nb(l 10) peaks and show a merging of these two peaks with decreasing periodicity.

Fabrication and study the effect of the laser on the properties of the compound Tl2-xHgxBa2-ySryCa2Cu3O10+δ superconductor

2018 ◽  
pp. 168
Author(s):  
A. Kareem Dahash Ali ◽  
Nihad Ali Shafeek
Keyword(s):  
Transition Temperature ◽  
Solid State ◽  
Hydrostatic Pressure ◽  
Electrical Properties ◽  
Co2 Laser ◽  
Temperature Shift ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural And Electrical Properties

This study included the fabrication of    compound (Tl2-xHgxBa2-ySryCa2Cu3O10+δ) in a manner solid state and under hydrostatic pressure ( 8 ton/cm2) and temperature annealing(850°C), and determine the effect of the laser on the structural and electrical properties elements in the compound, and various concentrations of x where (x= 0.1,0.2,0.3 ). Observed by testing the XRD The best ratio of compensation for x is 0.2 as the value of a = b = 5.3899 (A °), c = 36.21 (A °) show that the installation of four-wheel-based type and that the best temperature shift is TC= 142 K  .When you shine a CO2 laser on the models in order to recognize the effect of the laser on these models showed the study of X-ray diffraction of these samples when preparing models with different concentrations of the values ​​of x, the best ratio of compensation is 0.2 which showed an increase in the values ​​of the dimensions of the unit cell a=b = 5.3929 (A °), c = 36.238 (A°). And the best transition temperature after shedding laser is TC=144 K. 

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