X-Ray powder diffraction
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A considerable number of fatal intoxications have recently been connected with the growing popularity of new psychoactive substances (NPS). Therefore, there is a significant demand for the development of fast and facile field detection methods for NPS. These substances are often sold as blends (with inorganic or organic cutting agents), which may further complicate detection. X-Ray powder diffraction (XRPD) was evaluated as a suitable and easily employable analytical method for the identification of NPS. XRPD has been successfully used for the differentiation of eight synthetic cathinones with a similar molecular structure. Moreover, this method was also used for the identification of four drugs in authentic street samples. XRPD is a facile non-destructive method that can identify not only NPS in mixtures but also the cutting agents. The small amount of substances needed for the measurement, which can be re-used for other analyses, further enhances the versatility of this method.
In this work, we studied model stratum corneum lipid mixtures composed of the hydroxylated skin ceramides N-lignoceroyl 6-hydroxysphingosine (Cer[NH]) and α-hydroxylignoceroyl phytosphingosine (Cer[AP]). Two model skin lipid mixtures of the composition Cer[NH] or Cer[AP], N-lignoceroyl sphingosine (Cer[NS]), lignoceric acid (C24:0) and cholesterol in a 0.5:0.5:1:1 molar ratio were compared. Model membranes were investigated by differential scanning calorimetry and 2H solid-state NMR spectroscopy at temperatures from 25 °C to 80 °C. Each component of the model mixture was specifically deuterated for selective detection by 2H NMR. Thus, the exact phase composition of the mixture at varying temperatures could be quantified. Moreover, using X-ray powder diffraction we investigated the lamellar phase formation. From the solid-state NMR and DSC studies, we found that both hydroxylated Cer[NH] and Cer[AP] exhibit a similar phase behavior. At physiological skin temperature of 32 °C, the lipids form a crystalline (orthorhombic) phase. With increasing temperature, most of the lipids become fluid and form a liquid-crystalline phase, which converts to the isotropic phase at higher temperatures (65-80 °C). Interestingly, lignoceric acid in the Cer[NH]-containing mixture has a tendency to form two types of fluid phases at 65 °C. This tendency was also observed in Cer[AP]-containing membranes at 80 °C. While Cer[AP]-containing lipid models formed a short periodicity phase featuring a repeat spacing of d = 5.4 nm, in the Cer[NH]-based model skin lipid membranes, the formation of unusual long periodicity phase with a repeat spacing of d = 10.7 nm was observed.
- MeSH
- biologické modely MeSH
- ceramidy chemie metabolismus MeSH
- cholesterol chemie MeSH
- deuterium chemie MeSH
- hydroxylace fyziologie MeSH
- kůže chemie metabolismus MeSH
- lidé MeSH
- lipidové dvojvrstvy chemie metabolismus MeSH
- magnetická rezonanční spektroskopie metody MeSH
- permeabilita buněčné membrány MeSH
- prášková difrakce metody MeSH
- rentgenové záření MeSH
- teplota kůže fyziologie MeSH
- teplota MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
OBJECTIVE: To characterize the microstructure of two zinc phosphate cement formulations in order to investigate the role of liquid/solid ratio and composition of powder component, on the developed porosity and, consequently, on compressive strength. METHODS: X-ray powder diffraction with the Rietveld method was used to study the phase composition of zinc oxide powder and cements. Powder component and cement microstructure were investigated with scanning electron microscopy. Small angle neutron scattering (SANS) and microfocus X-ray computed tomography (XmCT) were together employed to characterize porosity and microstructure of dental cements. Compressive strength tests were performed to evaluate their mechanical performance. RESULTS: The beneficial effects obtained by the addition of Al, Mg and B to modulate powder reactivity were mitigated by the crystallization of a Zn aluminate phase not involved in the cement setting reaction. Both cements showed spherical pores with a bimodal distribution at the micro/nano-scale. Pores, containing a low density gel-like phase, developed through segregation of liquid during setting. Increasing liquid/solid ratio from 0.378 to 0.571, increased both SANS and XmCT-derived specific surface area (by 56% and 22%, respectively), porosity (XmCT-derived porosity increased from 3.8% to 5.2%), the relative fraction of large pores ≥50μm, decreased compressive strength from 50±3MPa to 39±3MPa, and favored microstructural and compositional inhomogeneities. SIGNIFICANCE: Explain aspects of powder design affecting the setting reaction and, in turn, cement performance, to help in optimizing cement formulation. The mechanism behind development of porosity and specific surface area explains mechanical performance, and processes such as erosion and fluoride release/uptake.
- MeSH
- difrakce rentgenového záření MeSH
- fosforečnany vápenaté MeSH
- kostní cementy MeSH
- maloúhlový rozptyl MeSH
- mikroskopie elektronová rastrovací MeSH
- pevnost v tlaku MeSH
- počítačová rentgenová tomografie * MeSH
- testování materiálů MeSH
- zinkfosfátový cement * MeSH
- zubní cementy * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Formulation of poorly water-soluble drugs with mesoporous silica has become a thriving field of pharmaceutics. The theoretical critical pore diameter has been introduced as a maximum value below which an undesired drug crystallization is suppressed by spatial confinement. Currently, only few values have been reported and study of fast crystallising drugs is missing especially at relevant storage temperatures. This study investigated the critical pore diameter of three model drugs with a poor glass-forming ability (i.e. haloperidol, carbamazepine and benzamide) using different mesoporous carriers (Parteck® SLC 500, Neusilin® US2, Syloid® XDP 3050 and Aeroperl® 300 Pharma) and subsequently monitored physical formulation stability over three months by X-ray powder diffraction. The selected drugs showed clear differences in their estimated critical pore diameters, whereas a temperature dependence was barely relevant for pharmaceutical storage conditions. Superior stability was noted for the formulations containing benzamide in line with its predicted relatively large critical pore diameter of 29.5 nm. Contrarily, impaired physical stability depending on drug loading was observed in the case of haloperidol representing a compound with a rather small critical pore diameter (8.4 nm). These findings confirm the importance of estimating the critical pore diameter, especially for poor glass-forming drugs.
Four different polymorphs, A, C, D, and E, of succinobucol were isolated and characterized by means of solid-state nuclear magnetic resonance spectroscopy, single crystal and powder X-ray diffraction, differential scanning calorimetry, thermogravimetry, and attenuated total reflection-infrared spectroscopy. From a number of experiments, the same polymorphs (C, D, and E) and an equilibrium phase mixture B consisting of polymorphs C and D were repeatedly gained using different solvents or their mixtures. Although polymorph A was obtained directly from recrystallization only on few occasions, polymorphs C, D, and E proved to be metastable kinetic polymorphs, which slowly transform to a thermodynamically more stable form A during long-term storage. The single-crystal structures of polymorph C and D were determined by X-ray single-crystal diffraction.
- MeSH
- diferenciální skenovací kalorimetrie MeSH
- krystalizace MeSH
- krystalografie rentgenová MeSH
- magnetická rezonanční spektroskopie MeSH
- molekulární modely MeSH
- prášková difrakce MeSH
- probukol analogy a deriváty analýza chemie MeSH
- spektrofotometrie infračervená MeSH
- termogravimetrie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The presence of impurities can drastically affect the efficacy and safety of pharmaceutical entities. p-Aminophenol (PAP) is one of the main impurities of paracetamol (PA) that can potentially show toxic effects such as maternal toxicity and nephrotoxicity. The removal of PAP from PA is challenging and difficult to achieve through regular crystallization approaches. In this regard, we report four new salts of PAP with salicylic acid (SA), oxalic acid (OX), l-tartaric acid (TA), and (1S)-(+)-10-camphorsulfonic acid (CSA). All the PAP salts were analyzed using single-crystal X-ray diffraction, powder X-ray diffraction, infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The presence of minute amounts of PAP in paracetamol solids gives a dark color to the product that was difficult to remove through crystallization. In our study, we found that the addition of small quantities of the aforementioned acids helps to remove PAP from PA during the filtration and washings. This shows that salt formation could be used to efficiently remove challenging impurities.
Analysis of C cross-polarization magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), and X-ray powder diffraction data of trospium chloride (TCl) products crystallized from different mixtures of water-ethanol [φ(EtOH) = 0.5-1.0] at various temperatures (0°C, 20°C) and initial concentrations (saturated solution, 30%-50% excess of solvent) revealed extensive structural variability of TCl. Although (13) C CP/MAS NMR spectra indicated broad variety of structural phases arising from molecular disorder, temperature-modulated DSC identified presence of two distinct components in the products. FTIR spectra revealed alterations in the hydrogen bonding network (ionic hydrogen bond formation), whereas the X-ray diffraction reflected unchanged unit cell parameters. These results were explained by a two-component character of TCl products in which a dominant polymorphic form is accompanied by partly separated nanocrystalline domains of a secondary phase that does not provide clear Bragg reflections. These phases slightly differ in the degree of molecular disorder, in the quality of crystal lattice and hydrogen bonding network. It is also demonstrated that, for the quality control of such complex products, (13) C CP/MAS NMR spectroscopy combined with factor analysis (FA) can satisfactorily be used for categorizing the individual samples: FA of (13) C CP/MAS NMR spectra found clear relationships between the extent of molecular disorder and crystallization conditions. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:1235-1248, 2013.
- MeSH
- benziláty chemie MeSH
- diferenciální skenovací kalorimetrie MeSH
- difrakce rentgenového záření MeSH
- krystalizace MeSH
- magnetická rezonanční spektroskopie MeSH
- nortropany chemie MeSH
- prášková difrakce MeSH
- spektroskopie infračervená s Fourierovou transformací MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
High-silica zeolites, some of the most important and widely used catalysts in industry, have potential for application across a wide range of traditional and emerging technologies. The many structural topologies of zeolites have a variety of potential uses, so a strong drive to create new zeolites exists. Here, we present a protocol, the assembly-disassembly-organization-reassembly (ADOR) process, for a relatively new method of preparing these important solids. It allows the synthesis of new high-silica zeolites (Si/Al >1,000), whose synthesis is considered infeasible with traditional (solvothermal) methods, offering new topologies that may find novel applications. We show how to identify the optimal conditions (e.g., duration of reaction, temperature, acidity) for ADOR, which is a complex process with different possible outcomes. Following the protocol will allow researchers to identify the different products that are possible from a reaction without recourse to repetitive and time-consuming trial and error. In developing the protocol, germanium-containing UTL zeolites were subjected to hydrolysis conditions using both water and hydrochloric acid as media, which provides an understanding of the effects of temperature and pH on the disassembly (D) and organization (O) steps of the process that define the potential products. Samples were taken from the ongoing reaction periodically over a minimum of 8 h, and each sample was analyzed using powder X-ray diffraction to yield a time course for the reaction at each set of conditions; selected samples were analyzed using transmission electron microscopy and solid-state NMR spectroscopy.
- MeSH
- anorganická chemie metody MeSH
- časové faktory MeSH
- difrakce rentgenového záření MeSH
- hydrolýza MeSH
- koncentrace vodíkových iontů MeSH
- magnetická rezonanční spektroskopie MeSH
- oxid křemičitý chemická syntéza MeSH
- prášky, zásypy, pudry MeSH
- teplota MeSH
- voda chemie MeSH
- zeolity chemická syntéza chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Drug loading into mesoporous carriers may help to improve the dissolution of poorly aqueous-soluble drugs. However, both preparation method and carrier properties influence loading efficiency and drug release. Accordingly, this study aimed to compare two preparation methods: formulation into liquisolid systems (LSS) and co-milling for their efficiency in loading the poorly soluble model drug cyclosporine A (CyA) into mesoporous magnesium aluminometasilicate Neusilin® US2 (NEU) or functionalized calcium carbonate (FCC). Scanning electron microscopy was used to visualize the morphology of the samples and evaluate the changes that occurred during the drug loading process. The solid-state characteristics and physical stability of the formulations, prepared at different drug concentrations, were determined using X-ray powder diffraction. In vitro release of the drug was evaluated in biorelevant media simulating intestinal fluid. The obtained results revealed improved drug release profiles of the formulations when compared to the milled (amorphous) CyA alone. The dissolution of CyA from LSS was faster in comparison to the co-milled formulations. Higher drug release was achieved from NEU than FCC formulations presumably due to the higher pore volume and larger surface area of NEU.
- MeSH
- difrakce rentgenového záření MeSH
- pomocné látky * MeSH
- poréznost MeSH
- rozpustnost MeSH
- voda * MeSH
- Publikační typ
- časopisecké články MeSH
Microporous Na-birnessite-type manganese oxides are synthesized by oxidation of Mn(OH)2 with K2S2O8 in strong alkaline environment. Subsequent ion-exchange reactions in aqueous solutions containing Sr, Ba promote their incorporation into the layered structural frameworks, which upon further hydration lead to the respective layered Buserites. Chemical composition and surface structure are assessed by X-ray powder diffraction, nitrogen- and argon- sorptiometry. Na-birnessites and Sr-buserites display good crystallinity. Ba-buserites consist mainly of nanocrystals. Their N2 adsorption/desorption isotherms of resemble IV-type isotherms. Integral and differential pore distribution curves obtained by N2-sorptiometry exhibit out-of-layers pores of 4-5 nm and 10-20 nm. Na-birnessites, Sr- and Ba-buserites possess external B.E.T surfaces of 75.6, 49.2 and 93.6 m2/g respectively. Considerable adsorption volumes of 14, 17 cm3/g for P/P0 = 0.05 for Na-birnessites and Ba-buserites are assessed by Ar-sorptiometry. Differential pore distribution curves confirm inner-layer micropores of 5 to 7 Å with a B.E.T specific area of 76.2 m²/g for Na-birnessites and 51.8 m²/g for Ba-buserites. Na-birnessites and Sr-, Ba-buserites possess enhanced ionic exchanging capacity, acting as a “sink” for heavy metal cations such as Fe2+, Fe3+, Co2+, Ni2+, As3+. The retention of U, Cs and Sr radioisotopes by them unfolds their salient anti-pollution potential for soil and subwater ecosystems.
- MeSH
- adsorpce MeSH
- baryum chemie MeSH
- difrakce rentgenového záření MeSH
- iontová výměna MeSH
- kationty MeSH
- minerály * chemie MeSH
- oxidy * chemická syntéza chemie MeSH
- povrchové vlastnosti MeSH
- sloučeniny manganu * chemie MeSH
- sodík chemie MeSH
- stroncium chemie MeSH
- Publikační typ
- práce podpořená grantem MeSH
