Search Results

You are looking at 11 - 20 of 43 items for :

  • Refine by Access: All Content x
Clear All
Pollack Periodica
Authors: Mohammed S. A. Khedr, Mona F. Ali, Abdullah M. A. Kamel, and Manal A. A. El-Ghanam

Abstract

This research will shed light on studying a terrazzo pavement in Prince Mohamed Ali Museum (the case study). The authors used visual inspection, stereo microscope, USB microscope, XRPD analysis, and SEM.EDX to identify its components, deterioration aspects and execution techniques. The XRPD and SEM.EDX results revealed that Portland cement was used in the three layers of terrazzo because of the detection of Hatrurite, Alite, Anorthite, Albite, Aragonite, etc. Many pigments were used in the topping terrazzo layer as; Goethite, Greenalite, Hematite, Azurite and Magnetite. The divider strips were made of brass alloy and the topping layer chips were prepared from basalt, marble and sea shells.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: G. Bruni, V. Berbenni, C. Milanese, A. Girella, P. Cofrancesco, G. Bellazzi, and A. Marini

Abstract  

In this work the solid-state characterization of anhydrous D-mannitol has been performed: α and β modifications can be distinguished only by XRPD and FTIR as they show melting temperature and enthalpy that are the same within the standard deviation. The understanding of the thermal behaviour of the δ form (obtained by re-crystallization in acetone) has required XRPD experiments performed at variable temperature. This form during heating undergoes a solid phase transition to α modification. By cooling a melted sample, under a wide range of experimental conditions, a very fast crystallization occurs. Independently of the starting crystal form (β or δ form), the re-crystallization of D-mannitol from melt always leads to α form.

Restricted access

The effect of physical state on the drug dissolution rate

Miscibility studies of Nimodipine with PVP

Journal of Thermal Analysis and Calorimetry
Authors: G. Papageorgiou, A. Docoslis, M. Georgarakis, and D. Bikiaris

Abstract  

In this work, the enhancement of drug dissolution rate through the preparation of new formulations containing Nimodipine in molecular level dispersion or in nanodispersion into poly(vinyl pyrrolidone) (PVP) matrix, was investigated. Differential scanning calorimetry (DSC) and modulated-temperature differential scanning calorimetry (MTDSC) in combination with X-ray powder diffractometry (XRPD) and scanning electron microscopy (SEM) studies showed that Nimodipine was amorphous in solid dispersions of 10 or 20 mass%, and mainly dispersed on a molecular level. This behaviour is attributed to the strong interactions taking place between the amine group of Nimodipine and carbonyl group of PVP. At higher drug loadings, crystal reflections in XRPD patterns and melting peaks of Nimodipine in DSC traces, indicated presence of drug in crystalline form. Micro-Raman studies in combination with SEM micrographs showed that the mean particle size increases with drug content in the formulations, up to 10 μm. Moreover, both XRPD patterns and micro-Raman spectra seem to indicate that Nimodipine crystallized in a second, thermodynamically stable, crystal modification II. The physicochemical characteristics of Nimodipine and the particle size distribution directly affect the dissolution rate enhancement, which is higher in amorphous dispersions.

Restricted access

Abstract  

The thermal behaviour of Co(II), Ni(II) and Zn(II)-containing zirconium phosphate of α type was investigated. XRPD analysis revealed that, for the samples containing Co(II) or Ni(II), the first reflection of the solid phase is split into a doublet. In contrast, when Zn(II) is present, a single solid phase system is formed. The thermal behaviour of the materials followed this sequence. For the samples containing Co(II) or Ni(II), phase-transition processes were found and there was also a loss of crystal water, but for the sample containing Zn(II) there was only one endothermic effect, which corresponded to the decomposition of phosphate groups.

Restricted access

Abstract  

Five polymorphs of chlorpropamide (α, β, δ, γ, and ε) were investigated near the melting point by using DSC. Structure of samples was tested by X-ray powder diffraction. Four first polymorphs were found to transform into ε-polymorph, which melts at T m=128°C, Δm H=24 kJ mol−1. Enthalpy of the polymorph transitions ranges from +3 kJ mol−1 for α→ε to −0.8 kJ mol−1 for β→ε. Structure of three first polymorphs was published elsewhere, and the structure of δ-polymorph is published for the first time. XRPD patterns for all polymorphs are reported, together with the atomic coordinates for the δ-polymorph.

Restricted access

Abstract  

Solvent and melt techniques were used to obtain molecular dispersion of the poorly soluble spironolactone (SPIR) model drug enhancing its dissolution rate. DSC study of the interaction between SPIR and hydroxypropyl-β-cyclodextrin confirmed the need for molecular dispersion if their complexation is required. Solvent-free twin-screw extrusion was suitable for forming inclusion complex significantly below the melting temperature of the SPIR. According to DSC, Raman and XRPD results fine dispersion of both components was achieved in a hydrophilic polymer. The molecules of the active ingredient are separated from each other in the polymer and the lack of the lattice energy causes faster dissolution.

Restricted access

Abstract  

Captopril (CAP) was the first commercially available angiotensine-converting enzyme (ACE) inhibitor. In the anti-hypertensive therapy is considered the selected drug has to be therapeutically effective together with reduced toxicity. CAP is an antihypertensive drug currently being administered in tablet form. In order to investigate the possible interactions between CAP and excipients in tablets formulations, differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis completed by X-ray powder diffraction (XRPD) and Fourier transform infrared spectroscopy (FTIR) were used for compatibility studies. A possible drug-excipient interaction was observed with magnesium stearate by DSC technique.

Restricted access

Abstract  

The thermal analytical study of venlafaxine hydrochloride, a third generation antidepressant, was investigated using thermogravimetry (TG) and differential scanning calorimetry (DSC). The DSC curves have shown a sharp endothermic event at 211 °C and TG demonstrated a single stage of mass loss between 254 and 283 °C. Solid-state characterization was carried out by DRIFT, SEM, and XRPD demonstrating the drug physicochemical properties including crystallinity. Drug-excipient compatibility studies investigated by DSC have shown a possible physical interaction of the drug with magnesium stearate, microcrystalline cellulose and starch. Nevertheless, these results where not confirmed by DRIFT and SEM analyses.

Restricted access

Abstract  

In the present study, we performed an investigation of phase transformation of zeolite Na-GIS in temperature interval from room temperature up to 1300C. The collapse of S4R and S8R (secondary building units in zeolite Na-GIS) and the forming of pure sodium nepheline phase, consists of S6R, was examined. During the thermal transformation of Na-GIS zeolite symmetry of rings was changed and their deformation increases. The irregularity of rings causes the appearance of defect modes in the IR spectra of amorphous precursors. Investigated phases were characterized by XRPD, IR, NMR and DSC methods. A semiempirical method AM1 was used for calculation of vibrational spectrum of nepheline.

Restricted access

Abstract  

A physico-chemical characterization of dipyridamole (C24H40N8O4), a widely used anti-aggregating agent, has been performed by using a combination of thermoanalytical (DSC) and spectroscopic (XRPD and FT-IR/PAS) techniques. A solid state transition, already reported in literature, has been ascribed to the breaking of an intramolecular H-bonds network. The rupture of a network of intermolecular H-bonds is thought to accompany the fusion. The solid state transition has been shown to be reversible provided the sample has not undergone melting. Mechanical milling and thermal annealing have been shown to decrease melting temperature and enthalpy. The effect brought about by mechanical and thermal treatment on the solid state transition is different. In the milled samples the transition peak shifts towards lower temperatures and its enthalpy suggests that all intramolecular H-bonds have been transformed into intermolecular H-bonds.

Restricted access