The present work is a concrete example of how physico-chemical studies, if performed in depth, are crucial to understand the behavior of pharmaceutical solids and constitute a solid basis for the control of the reproducibility of the industrial batches. In particular, a deep study of the thermal behavior of glipizide, a hypoglycemic drug, was carried out with the aim of clarifying whether the recognition of its polymorphic forms can really be done on the basis of the endothermic peak that the literature studies attribute to the melting of the compound. A number of analytical techniques were used: thermal techniques (DSC, TGA), X-ray powder diffraction (XRPD), FT-IR spectroscopy and scanning electron microscopy (SEM). Great attention was paid to the experimental design and to the interpretation of the combined results obtained by all these techniques. We proved that the attribution of the endothermic peak shown by glipizide to its melting was actually wrong. The DSC peak is no doubt triggered by a decomposition process that involves gas evolution (cyclohexanamine and carbon dioxide) and formation of 5-methyl-N-[2-(4-sulphamoylphenyl) ethyl] pyrazine-2-carboxamide, which remains as decomposition residue. Thermal treatments properly designed and the combined use of DSC with FT-IR and XRPD led to identifying a new polymorphic form of 5-methyl-N-[2-(4-sulphamoylphenyl) ethyl] pyrazine-2-carboxamide, which is obtained by crystallization from the melt. Hence, our results put into evidence that the check of the polymorphic form of glipizide cannot be based on the temperature values of the DSC peak, since such a peak is due to a decomposition process whose Tonset value is strongly affected by the particle size. Kinetic studies of the decomposition process show the high stability of solid glipizide at room temperature. 相似文献
Through this paper, we consider generated pseudo-operations of the following form: x⊕y=g−1(g(x)+g(y)), x⊙y=g−1(g(x)g(y)), where g is a continuous generating function. Pseudo-linear superposition principle, i.e., the superposition principle with this type of pseudo-operations in the core, for the Monge-Ampère equation is investigated. 相似文献
In this paper, the Authors study the small oscillations of an inviscid liquid under zero gravity in a container of revolution
with elastic bottom, considered as a membrane or a plate, and anchored edge. They obtain the equations of the displacements
of the free surface and the bottom and they reduce these equations to a functional equation in a suitable Hilbert space. By
using the methods of Functional Analysis the Authors prove the existence of the small oscillations.
Research partially supported by GNFM, MURST (Italy). 相似文献
The aim of this paper is to study sustainability of the pseudo-linear superposition principle, that is, of the nonlinear superposition principle (NLSP) observed in the pseudo-analysis? framework. The focus of this paper is on the so-called generated partial differential equation that is, for the purpose of this study, based on the stochastic Burger?s equation. 相似文献
The aim of this work was to search for new polymorphic forms of febantel, an anthelminthic drug of great present interest for the veterinary industry. Solvent-based recrystallization, thermal and mechanical treatments and spray drying were chosen to discover new solid forms. The solids obtained were physicochemically characterized by thermal techniques (DSC and TG), FTIR spectroscopy, laboratory and synchrotron X-ray powder diffraction and scanning electron microscopy. Our work leads to obtain a new solid form never described in the literature. In particular, the new polymorph was obtained by the anti-solvent method and the crystallization from isopropanol. The experimental conditions of crystallization favorable to the formation of the highest amount of the new solid phase were selected. The new phase shows a thermal, spectroscopic and diffractometric behavior unique. Furthermore, the preliminary structure investigation suggests two possible crystal systems: an orthorhombic or a monoclinic one, with really comparable lattice parameters and cell volume. Measurements put into evidence that the new phase is a metastable polymorph that is in monotropic relationship with the stable and known form.
Al-doped lithium manganese spinels, with starting composition Li1.02AlxMn1.98−xO4 (0.00<x≤0.06), are investigated to determine the influence of the Al3+ doping on the Jahn-Teller (J-T) cooperative transition temperature TJ-T. X-ray powder diffraction (XRPD), nuclear magnetic resonance, electron paramagnetic resonance, conductivity and magnetic susceptibility data are put into relation with the tetrahedral and octahedral occupancy fraction of the spinel sites and with the homogeneous distribution of the Al3+ ions in the spinel phase. It is observed that Al3+ may distribute between the two cationic sublattices. The J-T distortion, associated with a drop of conductivity near room temperature in the undoped sample, is shifted towards lower temperature by very low substitution. However, for x>0.04 TJ-T it increases with increasing x, as clearly evidenced in low temperature XRPD observations. A charge distribution model in the cationic sublattice, for Al substitution, is proposed to explain this peculiar behavior. 相似文献
Journal of Thermal Analysis and Calorimetry - The eco-friendly method of kneading was here used to synthesize a cocrystal of probenecid, an uricosuric drug used in treating gout and hyperuricemia,... 相似文献
Group B Streptococcus serotypes Ia and Ib capsular polysaccharides are key targets for vaccine development. In spite of their immunospecifity these polysaccharides share high structural similarity. Both are composed of the same monosaccharide residues and differ only in the connection of the Neu5Acα2-3Gal side chain to the GlcNAc unit, which is a β1-4 linkage in serotype Ia and a β1-3 linkage in serotype Ib. The development of efficient regioselective routes for GlcNAcβ1-3[Glcβ1-4]Gal synthons is described, which give access to different group B Streptococcus (GBS) Ia and Ib repeating unit frameshifts. These glycans were used to probe the conformation and molecular dynamics of the two polysaccharides, highlighting the different presentation of the protruding Neu5Acα2-3Gal moieties on the polysaccharide backbones and a higher flexibility of Ib polymer relative to Ia, which can impact epitope exposure. 相似文献