Obtaining high purity silica from rice hulls

Many routes for extracting silica from rice hulls are based on direct calcining. These methods, though, often produce silica contaminated with inorganic impurities. This work presents the study of a strategy for obtaining silica from rice hulls with a purity level adequate for applications in electronics. The technique is based on two leaching steps, using respectively aqua regia and Piranha solutions, which extract the organic matrix and inorganic impurities. The material was characterized by Fourier-transform infrared spectroscopy (FTIR), powder x-ray diffraction (XRD), x-ray fluorescence (XRF), scanning electron microscopy (SEM), particle size analysis by laser diffraction (LPSA) and thermal analysis

Spectrophotometric and HPLC determination of deflazacort in pharmaceutical dosage forms

Deflazacort (DFZ) is a glucocorticoid used as an anti-inflammatory and immunosuppressant drug. No official methods are available for DFZ determination in pharmaceutical formulations. The objective of this study was to develop, validate and compare spectrophotometric (UV and colorimetric) and high-performance liquid chromatography (HPLC) methods, for the quantitative determination of DFZ in tablets and oral suspension. For the UV method, ethanol was used as the solvent, with detection at 244 nm. The colorimetric method was based on the redox reaction with blue tetrazolium in alkaline medium, with detection at 524 nm. The method by HPLC was carried out using a C18 column, mobile phase consisting of acetonitrile:water (80:20, v/v) with a flow rate of 1.0 mL min-1 and detection at 244 nm. The methods proved linear (r > 0.999), precise (RSD 97%). Statistical analysis of the results indicated that the UV and HPLC methods were statistically equivalent, while the values obtained for the colorimetric method differed significantly from the other methods.O deflazacorte (DFZ) é um fármaco glicocorticóide usado como antiinflamatório e imunossupressor. Métodos oficiais não estão disponíveis para a determinação de DFZ em formas farmacêuticas. Este estudo teve como objetivo desenvolver, validar e comparar métodos por espectrofotometria (UV e colorimetria) e cromatografia líquida de alta eficiência (CLAE), na determinação quantitativa de DFZ em comprimidos e suspensão oral. O método por UV utilizou etanol como solvente, com detecção em 244 nm. O método colorimétrico foi baseado na reação de redução com azul de tetrazólio em meio alcalino, com detecção em 524 nm. O método por CLAE utilizou coluna C18; fase móvel constituída de acetonitrila:água (80:20, v/v), com fluxo de 1,0 mL min-1 e detecção em 244 nm. Os métodos foram lineares (r > 0,999); precisos (RSD 97%). As análises estatísticas dos resultados obtidos indicaram que os métodos por UV e por CLAE foram estatisticamente equivalentes, enquanto os valores obtidos para o método colorimétrico diferiram significativamente dos demais métodos

Grinding effect on levofloxacin hemihydrate

The grinding techniques were used in different pharmacotechnical process. the control of the effect of grinding in solid state properties of drugs is very important, mainly in hydrated drugs. Levofloxacin hemihydrate (LVF) is a good example of this type of compounds and a broad spectrum antibiotic of the fluoroquinolone drug class. the samples of LVF with and without grinding were studied using different characterization techniques such as thermogravimetry, differential scanning calorimetry, fourier-transformed infrared, X-ray powder diffraction, and hot stage microscopy. the purpose of the present study was to evaluate the effects of grinding in the dehydration and rehydration processes in levofloxacin hemihydrate. After heating, the samples lost water molecules and the rehydration process was modified depending on defects due to the grinding. At room temperature, the complete transformation to the hemihydrate form was detected only for the sample without grinding. On the other hand, the milled sample showed two phases, hydrate and anhydrate forms. Therefore, the defects in the crystalline structure would cause the irreversible transformation.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Univ Fed Santa Catarina, PGFAR, BR-88040970 Florianopolis, SC, BrazilNatl Univ Cordoba, Fac Math Astron & Phys FAMAF, Cordoba, ArgentinaUniv Fed Santa Catarina, BR-88040970 Florianopolis, SC, BrazilUniversidade Federal de São Paulo, Inst Ciencia & Tecnol, São Paulo, BrazilUniversidade Federal de São Paulo, Inst Ciencia & Tecnol, São Paulo, BrazilWeb of Scienc

Isomorphous Salts of Anti-HIV Saquinavir Mesylate: Exploring the Effect of Anion-Exchange on Its Solid-State and Dissolution Properties

Saquinavir (SQV) is an important protease inhibitor used for AIDS/HIV antiretroviral therapy. As a free base it is almost insoluble in water, and it is commercialized as its mesylate salt (SQVM), classified as belonging to class IV (low permeability and solubility). Anion exchange has been used in this work to explore the effect of halides replacing the mesylate anion on the solid state and solubility properties of saquinavir at ambient temperature. All solid forms obtained were characterized via X-ray single crystal and powder diffraction, and their thermal behavior was analyzed via differential scanning calorimetry, thermogravimetric analysis, hot-stage microscopy and variable temperature X-ray powder diffraction. Saquinavir chloride (SQVCl), saquinavir bromide (SQVBr), and saquinavir iodide (SQVI) are all hydrates, the difference in the anion size being responsible for the different number of water molecules (3, 2, and 1, respectively). Dissolution properties have also been investigated, and it has been found that the behavior in water of SQVM and SQVCl are very similar, with 43 and 38% dissolved in 90 min, respectively, whereas for SQVBr and SQVI this percentage was 31 and 18%, respectively. Solid SQVCl could therefore be used as a valid alternative to current pharmaceutical formulations