Validation of a stability indicating capillary electrophoresis method for the determination of darunavir in tablets and comparison with the of infrared absorption spectroscopic method

Darunavir (DRV) is a protease inhibitor used in the treatment of HIV infection, which constitutes a keystone in the therapy of patients infected with this virus. There is no monograph described in official compendia. The literature provides few methods of analysis for the determination of DRV in pharmaceuticals which include TLC, IR, UPLC, HPLC, HPLC-MS, HPLC-MS/MS, but there are no reports of the use of capillary electrophoresis (CE) for the determination of this drug. Thus, this research proposed the development and validation of a CE method for the determination of DRV in tablets. The method was completely validated according to the International Conference on Harmonization guidelines, showing linearity, selectivity, precision, accuracy and robustness. The migration was achieved in less than 1 minute using fused-silica uncoated capillary with an id of 50 μm and total length of 21 cm and voltage of +20 kV. The sample injection was performed in the hydrodynamic mode. The method was linear over the concentration range of 50-200 μg mL-1 with correlation coefficient 0.9998 and limits of detection and quantification of 7.29 and 22.09 μg mL-1, respectively. The drug was subjected to acid, base, oxidation and photolysis degradation. Degradation products were found interfering with the assay of DRV, therefore the method can be regarded as stability indicating. The validated method is useful and appropriate for the routine quality control of DRV in tablets.

Study of a series of cobalt(II) sulfonamide complexes: Synthesis, spectroscopic characterization, and microbiological evaluation against M. tuberculosis. Crystal structure of [Co(sulfamethoxazole)2(H 2O)2]·H2O

Nowadays, the research for new and better antimicrobial compounds is an important field due to the increase of immunocompromised patients, the use of invasive medical procedures and extensive surgeries, among others, that can affect the incidence of infections. Another big problem associated is the occurrence of drug-resistant microbial strains that impels a ceaseless search for new antimicrobial agents. In this context, a series of heterocyclic- sulfonamide complexes with Co(II) was synthesized and characterized with the aim of obtaining new antimicrobial compounds. The structural characterization was performed using different spectroscopic methods (UV-Vis, IR, and EPR). In spite of the fact that the general stoichiometry for all the complexes was Co(sulfonamide)2·nH2O, the coordination atoms were different depending on the coordinated sulfonamide. The crystal structure of [Co(sulfamethoxazole)2(H2O)2]·H 2O was obtained by X-ray diffraction showing that Co(II) is in a slightly tetragonal distorted octahedron where sulfamethoxazole molecules act as a head-to-tail bridges between two cobalt atoms, forming polymeric chains. Besides, the activity against Mycobacterium tuberculosis, one of the responsible for tuberculosis, and the cytotoxicity on J774A.1 macrophage cells were evaluated. © 2012 Elsevier B.V. All rights reserved.

Chemical and thermal influence of the [4Fe-4S](2+) cluster of A/G-specific adenine glycosylase from Corynebacterium pseudotuberculosis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Polymeric precursor method to the synthesis of XWO(4) (X = Ca and Sr) thin films-Structural, microstructural and spectroscopic investigations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural and spectroscopic characterization of Al2-xCrxO3 powders obtained by polymeric precursor method

Al2O3 and Al2-x Cr (x) O-3 (x = 0.01, 0.02 and 0.04) powders have been synthesized by the polymeric precursors method. A study of the structural evolution of crystalline phases corresponding to the obtained powders was accomplished through X-Ray Diffraction and UV-vis spectroscopy (reflectance spectra and CIEL* a*b* color data). The obtained results allow to identify the gamma-Al2O3 to alpha-Al2O3 phase transition. The single-phase alpha-Al2O3 powder was obtained after heat treatment at 1050 degrees C for 2 h. The results show that the green to red color transition and ruby luminescence lines observed for the powders of Al2-x Cr (x) O-3 are related to the gamma to alpha-Al2O3 phase transition and the temperature and time range for such transition depends on the chromium content.

Correlation between the spectroscopic and structural properties with the occupation of Eu3+ sites in powdered Eu3+-doped LiTaO3 prepared by the Pechini method

In this work we studied the structural and optical properties of lithium tantalate (LiTaO3) powders doped with Eu3+ ions. We have examined the different sites occupied by the rare earth ion through the correlation of the DRX data analyzed with the Rietveld method and some spectroscopic parameters derived from the Eu3+ luminescence. Adirect relation was established between the lattice parameters and the occupation fraction of Eu3+ in each LiTaO3 site. The occupation fraction was set as the relative population of Eu3+ ions for each site obtained by means of the intensity, baricenter, and the spontaneous emission coefficients of the D-5(0)-> F-7(0) transitions. We concluded that the unit cell parameter a presents the same behavior of the Eu3+ occupation fraction in Ta5+ sites as a function of the Eu3+ content in LiTaO3. The same was observed for the variation in Eu3+ occupation fraction in the Li+ site and the unit cell parameter c with the Eu3+ content. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3204967]

Multi-spectroscopic monitoring of cisplatin-derived species delivery from ureasil polyether hybrid matrix

Driven by the challenges involved in the development of new advanced materials with unusual drug delivery profiles capable of improving the therapeutic and toxicological properties of existing cancer chemotherapy, the one-pot sol-gel synthesis of flexible, transparent and insoluble urea-cross-linked polyether-siloxane hybrids has been recently developed. In this one-pot synthesis, the strong interaction between the antitumor cisplatin (CisPt) molecules and the ureasil-poly(propylene oxide) (PPO) hybrid matrix gives rise to the incorporation and release of an unknown CisPt-derived species, hindering the quantitative determination of the drug release pattern from the conventional UV-Vis absorption technique. In this article, we report the use of an original synchrotron radiation calibration method based on the combination of XAS and UV-Vis for the quantitative determination of the amount of Pt-based molecules released in water. Thanks to the combination of UV-Vis, XAS and Raman techniques, we demonstrated that both the CisPt molecules and the CisPt-derived species are loaded into an ureasil-PPO/ureasil-poly(ethylene oxide) (PEO) hybrid blend matrix. The experimentally determined molar extinction coefficient of the CisPt-derived species loaded into ureasil-PPO hybrid matrix enabled the simultaneous time-resolved monitoring of each Pt species released from this hybrid blend matrix.

Carbon nuclear magnetic resonance spectroscopic fingerprinting of commercial gasoline: Pattern-recognition analyses for screening quality control purposes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Structural and Spectroscopic Studies of Pr3+-Doped GdAlO3

In this work, GdAlO3:Pr3+ was successfully prepared by the Pechini method at lower temperatures when compared to others methods such as solid-state synthesis and sol-gel process. In accordance to the XRD data, the fully crystalline single-phase GdAlO3 could be obtained at 900 degrees C. Luminescence measurements indicate Gd -> Pr3+ energy transfer. In the emission spectra, the P-3(0) ->(3) H-4 (blue emission) and D-1(2) ->(3) H-4 (red emission) transitions of Pr3+ ions can be observed and the ratio between their intensities depends on the Pr3+ content due to the cross-relaxation phenomenon.

Screening Brazilian commercial gasoline quality by hydrogen nuclear magnetic resonance spectroscopic fingerprintings and pattern-recognition multivariate chemometric analysis

The identification of gasoline adulteration by organic solvents is not an easy task, because compounds that constitute the solvents are already in gasoline composition. In this work, the combination of Hydrogen Nuclear Magnetic Resonance ((1)H NMR) spectroscopic fingerprintings with pattern-recognition multivariate Soft Independent Modeling of Class Analogy (SIMCA) chemometric analysis provides an original and alternative approach to screening Brazilian commercial gasoline quality in a Monitoring Program for Quality Control of Automotive Fuels. SIMCA was performed on spectroscopic fingerprints to classify the quality of representative commercial gasoline samples selected by Hierarchical Cluster Analysis (HCA) and collected over a 6-month period from different gas stations in the São Paulo state, Brazil. Following optimized the (1)H NMR-SIMCA algorithm, it was possible to correctly classify 92.0% of commercial gasoline samples, which is considered acceptable. The chemometric method is recommended for routine applications in Quality-Control Monitoring Programs, since its measurements are fast and can be easily automated. Also, police laboratories could employ this method for rapid screening analysis to discourage adulteration practices. (C) 2010 Elsevier B.V. All rights reserved.

Spectroscopic study of ejected dental tissue after Er : YAG laser ablation

By means of IR spectroscopy, we determined the teeth ablation mechanism by an Er:YAG laser oscillating at 2.94 mum. Ejected dental material, ablated by the laser from human teeth, was deposited on an IR window and the absorption spectra were measured in the range 2500-20,000 nm. Sound teeth were used, and the corresponding film spectra were compared to spectra obtained by traditional methods. The films spectra obtained do not differ appreciably from those obtained by the traditional method for sound teeth, indicating that the material ejected by an Er:YAG represents the tooth condition.The obtained results confirm that a spectroscopic analysis of a tooth treated with an Er:YAG laser can be done measuring the absorbance of a film composed of ejected material without the need to slice it. In addition, we could determine that the laser absorption occurs mainly by the interstitial water, and the temperature elevation of the ejected material does not exceed 60degreesC. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Structural and spectroscopic analysis of gamma-Al2O3 to alpha-Al2O3-CoAl2O4 phase transition

Co-doped alumina powders were synthesized by means of the polymeric precursor method to obtain ceramic pigments. The effect of different contents of Co2+ on phase transition gamma to alpha-Al2O3 and appearing of CoAl2O4 spinel were studied by means of X-ray diffraction. A partial phase diagram of the system CoAl2O3 was proposed from these data by means of determination of the percentages of these phases according to the calcining temperature. Critical particle size to phase transition was determined by means of calculations of crystallite size and determination of superficial area through the BET method. UV-vis spectroscopy of the samples allow to compare the band shift with the phase transition. Besides, a study of thermal stability and intensity of the blue coloration of the synthesized powders with the presence of cobalt in relation to the calcining temperature was accomplished and compared to the phase transition. The results show that the higher blue color intensity was obtained for the powders with Co-doped gamma-Al2O3 closest of phase transition to alpha-Al2O3 + CoAl2O4. (c) 2005 Elsevier B.V. All rights reserved.

A laser-induced fluorescence spectroscopic study of organic matter in a Brazilian Oxisol under different tillage systems

Laser-induced fluorescence (LIF) spectroscopy has been proposed as new method for determining the degree of humification of organic matter (OM) in whole soils. It can be also used to analyze the OM in whole soils containing large amounts of paramagnetic materials, and which are neither feasible to Electron Paramagnetic Resonance (EPR) nor to C-13 Nuclear Magnetic Resonance (NMR) spectroscopy. In the present study, 3 LIF spectroscopy was used to investigate the OM in a Brazilian Oxisol containing high concentration of Fe+3. Soil samples were collected from two areas under conventional tillage (CT), two areas under no-till management (NT) and from a non-cultivated (NC) area under natural vegetation. The results of LIF spectroscopic analysis of the top layer (0-5 cm) of whole soils showed a less aromatic OM in the non-cultivated than in the cultivated soils. This is consistent with data corresponding to HA samples extracted from the same soils and analyzed by EPR, NMR and conventional fluorescence spectroscopy. The OM of whole soils at 5-10 and 10-20 cm depth was also characterized by LIF spectroscopy.Analysis of samples of NT and NC soils showed a higher OM aromatic content at depth. This is a consequence of the accumulation of plant residues at the soil surface in quantities that are too large for microorganisms to metabolize fully, thus, resulting in less aromatic or less hurnified humic substances. In deeper soil layers, the input of residues was lower and further decomposition of humic substances by microorganisms continued, and the aromaticity and degree of humification increased with soil depth. This data indicates that the gradient of humification of OM in the NT soil was similar to those observed in natural soils. Nevertheless, the degree of humification of the OM in the soils under no-till management varied less than that corresponding to non-cultivated soils. This may be because the former have been managed under these practices for only 5 years, in contrast to the continuous humification process occurring in the natural soils. on the other band, LIF spectroscopic analysis of the CT soils showed less pronounced changes or no change in the degree of humification with depth. This indicates that the ploughing and harrowing involved in CT lead to homogenization of the soil and thereby also of the degree of humification of OM throughout the profile. (c) 2006 Elsevier B.V. All rights reserved.

Spectroscopic properties of Yb3+ doped PbO-Bi2O3-Ga2O3 glasses for IR laser applications

PbO-Bi2O3-Ga2O3 glasses doped with different concentrations of Yb3+ are presented. The spectroscopic properties and laser parameters are calculated and a comparison between different results obtained when calculating the Yb3+ emission cross-section with the reciprocity method and with the Fuchtbauer-Ladenburg formula is presented. The behavior of the near-infrared luminescence is described theoretically by a rate equation and compared with the experimental results. This host doped with Yb3+ is a promising material for laser action at 1019 nm, with properties similar to other known glasses used as active laser media; the emission cross-section of 1.1 x 10(-20) cm(2), the high absorption cross-section (of 2.0 x 10(-20) cm(2)) and a minimum pump intensity of 2.4 kW/cm(2) are interesting properties for short pulse generation. (C) 2005 Elsevier B.V. All rights reserved.

Chemical, spectroscopic characterization, and in vitro antibacterial studies of a new gold(I) complex with N-acetyl-L-cysteine

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)