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Phosphate Solution (phosphate + solution)
Selected AbstractsConversion of Tetranary Borate Glasses to Phosphate Compounds in Aqueous Phosphate SolutionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008Wenhai Huang In our earlier work, it was found that particles of a ternary alkali-borate glass, containing either CaO or BaO, converted completely to a crystalline phosphate of calcium or barium when reacted in an aqueous phosphate solution at 37°C. The present work is an extension of our earlier work to investigate the conversion of tetranary borate glass with the composition 10Li2O·10CaO·10(AeO or T2O3)·60B2O3 (weight percent), where Ae is the alkai-earth metal Mg or Ba, and T is the transition metal La, Sm, or Dy. In the experiments, particles of each glass (150,300 ,m) were reacted in 0.25M K2HPO4 solution with a starting pH of ,9.0 at 37°C. Weight loss and pH measurements indicated that the reaction was complete after 30,50 h, yielding an amorphous product. X-ray fluorescence showed that the as-formed product consisted of a calcium phosphate phase that contained the alkali-earth metal or transition metal present in the starting glass. Heating the as-formed material for 8 h at 600°,700°C produced a mixture of two crystalline phosphates: calcium phosphate and an alkali-earth or transition metal phosphate. The kinetics and mechanism of converting tetranary borate glass to phosphate materials are discussed and compared with data from earlier work for the conversion of ternary borate glass. [source] Conversion of Bioactive Borosilicate Glass to Multilayered Hydroxyapatite in Dilute Phosphate SolutionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2007Yadong Li The conversion of a bioactive borosilicate glass in aqueous phosphate solution was observed to produce vastly different reaction kinetics and hydroxyapatite (HA) microstructures, depending on whether the glass was reacted continuously or intermittently in the solution. Particles (150,300 ,m) of a borosilicate glass (designated H12) were reacted continuously or intermittently in 0.25M K2HPO4 solution with a starting pH value of 7.0 at 37°C. The conversion kinetics of the glass particles to HA were determined from weight loss measurements. Structural and compositional changes resulting from the conversion reaction were characterized using scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis, and Fourier transform infrared spectroscopy. For conversion experiments carried out intermittently (12,24 h intervals, followed by drying), faster reaction kinetics and a unique multilayered microstructure, consisting of alternating layers of HA and an amorphous SiO2 -rich material with nearly uniform thickness (2,3 ,m), were observed. On the other hand, particles reacted continuously in the phosphate solution for the same total time converted more slowly and produced a single HA layer. The kinetics and mechanism of forming HA under the intermittent and continuous reaction conditions are described and compared with those for bioactive silicate and borate glasses studied in previous work. [source] Quantitation of talinolol and other ,-blockers by capillary electrophoresis for in vitro drug absorption studiesELECTROPHORESIS, Issue 15 2003Bilal Awadallah Abstract A capillary zone electrophoresis method is described for the enantioseparation of talinolol using heptakis(2,3-diacetyl-6-sulfo)-,-cyclodextrin (HDAS-,-CD) as a chiral selector. After liquid-liquid extraction of talinolol from physiological solution, electrokinetic injection was employed to improve the sensitivity. The use of a coated capillary was necessary to achieve stable and reproducible enantioseparations. A baseline separation of the talinolol enantiomers was achieved in less than 10 min using 100 mM phosphate solution as background electrolyte and pH 3.5, at the presence of 3.0 mM HDAS-,-CD and at 20°C. In addition, this analytical condition proved to be useful for the enantioseparation of a number of other ,-blocking agents such as alprenolol, atenolol, bisoprolol, celiprolol, metipranolol, oxprenolol, and sotalol. For determing talinolol, the method could be validated in terms of precision, accuracy and linearity, and was found to be suitable in determination of talinolol enantiomers in highly diluted samples obtained from in vitro experiments. [source] Estimation of phosphate adsorption by Acrisols of western Spain from electrical conductivity of potassium dihydrogen phosphate extracts of soilEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2001R. Espejo Serrano Summary Estimation of the phosphate adsorption capacity in highly weathered acid soils is crucial for adopting appropriate phosphate fertilization practices. In this work, the salt sorption effect was used to develop a method for estimating phosphate adsorption capacity from the decrease in electrical conductivity of a potassium dihydrogen phosphate solution brought in contact with acidic soil samples from surface and subsurface horizons of Acrisols. The method is fast and simple and requires only the use of a conductimeter. [source] Growth of osteoblast-like cells on biomimetic apatite-coated chitosan scaffoldsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2008I. Manjubala Abstract Porous scaffold materials that can provide a framework for the cells to adhere, proliferate, and create extracellular matrix are considered to be suitable materials for bone regeneration. Interconnected porous chitosan scaffolds were prepared by freeze-drying method, and were mineralized by calcium and phosphate solution by double-diffusion method to form nanoapatite in chitosan matrix. The mineralized chitosan scaffold contains hydroxyapatite nanocrystals on the surface and also within the pore channels of the scaffold. To assess the effect of apatite and porosity of the scaffolds on cells, human osteoblast (SaOS-2) cells were cultured on unmineralized and mineralized chitosan scaffolds. The cell growth on the mineralized scaffolds and on the pure chitosan scaffold shows a similar growth trend. The total protein content and alkaline phosphatase enzyme activity of the cells grown on scaffolds were quantified, and were found to increase over time in mineralized scaffold after 1 and 3 weeks of culture. The electron microscopy of the cell-seeded scaffolds showed that most of the outer macropores became sealed off by a continuous layer of cells. The cells spanned around the pore wall and formed extra cellular matrix, consisting mainly of collagen in mineralized scaffolds. The hydroxyproline content also confirmed the formation of the collagen matrix by cells in mineralized scaffolds. This study demonstrated that the presence of apatite nanocrystals in chitosan scaffolds does not significantly influence the growth of cells, but does induce the formation of extracellular matrix and therefore has the potential to serve for bone tissue engineering. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] Transformation of 3DP gypsum model to HA by treating in ammonium phosphate solutionJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2007Rungnapa Lowmunkong Abstract Three-dimensional printing (3DP) is a CAD/CAM built-up using ink-jet printing technique. Commercially available 3DP system can form only gypsum model and not for bioceramics. On the other hand, transformation of hardened gypsum into hydroxyapatite (HA) by treatment in ammonium phosphate solution was found lately. In the present study, transformation of the 3DP gypsum block to HA was attempted. However, the fabricated 3DP block was soluble in water. To insolubilize, it was heated at 300°C for 10 min, and then, gypsum was transformed to calcium sulfate hemihydrate, CaSO4 · 0.5H2O. The 3D block was immersed in 1M (NH4)3PO4 · 3H2O solution at 80°C for 1,24 h, and the transformation into HA within 4 h was ascertained. A heat-treated plaster of Paris (POP) block was also investigated for comparison. The unheated POP block consisting of gypsum dihydrate took 24 h to complete the transformation, while the heat-treated POP consisting calcium sulfate hemihydrate promoted the transformation into HA; but the transformed thickness in the block was less than the 3DP block. This is probably due to higher solubility of the hemihydrate than gypsum dihydrate. Accelerated transformation of the 3DP block was also caused by its porous structure, which enabled an easy penetration of the phosphate solution. With the present method, it is possible to transform the fabricated gypsum by 3D printing that is adaptive to the osseous defect into HA prostheses or scaffold. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007 [source] Raman spectroscopy of hydrotalcites with phosphate in the interlayer: implications for the removal of phosphate from waterJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2006Ray L. Frost Abstract Hydrotalcites with phosphate in the interlayer were prepared at different pH values. At pH > 11.0 (PO4)3, was the intercalated ionic species, whereas at pH < 11.0 a mixture of (PO4)3, and (HPO4)2, ions was intercalated. Powder X-ray diffraction shows that the hydrotalcite formed at pH 9.5 is poorly diffracting with a d-spacing of 11.9 Å; whereas the d(003) spacing for the phosphate interlayered hydrotalcite formed at pH 11.9 and 12.5 was 8.0 and 7.9 Å respectively. The addition of a thermally activated ZnAl-HT to a phosphate solution resulted in the uptake of the phosphate and the reformation of the hydrotalcite. Raman spectroscopy of the phosphate interlayered hydrotalcites shows that the interlayered anion is pH dependent and only above pH 11.9 is the orthophosphate anion intercalated. At lower pH, the monohydrogen phosphate anion is intercalated. Raman spectroscopy shows that upon addition of the thermally activated hydrotalcite to an aqueous phosphate solution, results in the uptake of phosphate anion from the solution. Copyright © 2006 John Wiley & Sons, Ltd. [source] Conversion of Tetranary Borate Glasses to Phosphate Compounds in Aqueous Phosphate SolutionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008Wenhai Huang In our earlier work, it was found that particles of a ternary alkali-borate glass, containing either CaO or BaO, converted completely to a crystalline phosphate of calcium or barium when reacted in an aqueous phosphate solution at 37°C. The present work is an extension of our earlier work to investigate the conversion of tetranary borate glass with the composition 10Li2O·10CaO·10(AeO or T2O3)·60B2O3 (weight percent), where Ae is the alkai-earth metal Mg or Ba, and T is the transition metal La, Sm, or Dy. In the experiments, particles of each glass (150,300 ,m) were reacted in 0.25M K2HPO4 solution with a starting pH of ,9.0 at 37°C. Weight loss and pH measurements indicated that the reaction was complete after 30,50 h, yielding an amorphous product. X-ray fluorescence showed that the as-formed product consisted of a calcium phosphate phase that contained the alkali-earth metal or transition metal present in the starting glass. Heating the as-formed material for 8 h at 600°,700°C produced a mixture of two crystalline phosphates: calcium phosphate and an alkali-earth or transition metal phosphate. The kinetics and mechanism of converting tetranary borate glass to phosphate materials are discussed and compared with data from earlier work for the conversion of ternary borate glass. [source] Effect of pH on the Carbonate Incorporation into the Hydroxyapatite Prepared by an Oxidative Decomposition of Calcium,EDTA ChelateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2008Yusuf Yusufoglu In this study, the carbonate incorporation into the hydroxyapatite (HAp) lattice under various pH conditions was investigated. Crystalline-sodium and carbonate-containing calcium HAp (NaCO3HAp) powders were prepared using an oxidative decomposition of calcium,EDTA chelates in a sodium phosphate solution with hydrogen peroxide. The powders obtained were characterized by X-ray diffraction, infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and elemental analysis. Depending on pH, spherical particles approximately 3.5 ,m in diameter or hexagonal prismatic particles measuring 3,9 ,m in length were obtained. Various characterization techniques showed that the precipitates were a single-phase NaCO3HAp. The carbonate content and the lattice parameters of the HAp were a function of solution pH. Maximum carbonate incorporated into the HAp lattice was at pH=10, corresponding to lattice parameters of a=0.93880 nm and c=0.69070 nm. Furthermore, spectroscopic analyses indicate that the as-prepared samples are B-type carbonated HAp, in which carbonate ions occupy the phosphate sites. After heat treatment at 965°C, most of the carbonate is removed from the HAp lattice. [source] Conversion of Bioactive Borosilicate Glass to Multilayered Hydroxyapatite in Dilute Phosphate SolutionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2007Yadong Li The conversion of a bioactive borosilicate glass in aqueous phosphate solution was observed to produce vastly different reaction kinetics and hydroxyapatite (HA) microstructures, depending on whether the glass was reacted continuously or intermittently in the solution. Particles (150,300 ,m) of a borosilicate glass (designated H12) were reacted continuously or intermittently in 0.25M K2HPO4 solution with a starting pH value of 7.0 at 37°C. The conversion kinetics of the glass particles to HA were determined from weight loss measurements. Structural and compositional changes resulting from the conversion reaction were characterized using scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis, and Fourier transform infrared spectroscopy. For conversion experiments carried out intermittently (12,24 h intervals, followed by drying), faster reaction kinetics and a unique multilayered microstructure, consisting of alternating layers of HA and an amorphous SiO2 -rich material with nearly uniform thickness (2,3 ,m), were observed. On the other hand, particles reacted continuously in the phosphate solution for the same total time converted more slowly and produced a single HA layer. The kinetics and mechanism of forming HA under the intermittent and continuous reaction conditions are described and compared with those for bioactive silicate and borate glasses studied in previous work. [source] Chemically Bonded Phosphate Ceramics: I, A Dissolution Model of FormationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2003Arun S. Wagh This is the first of three papers in which the kinetics of formation of chemically bonded phosphate ceramics is discussed. A literature survey indicates that the formation of such ceramics is a three-step process. First, oxides dissolve in a phosphoric acid or an acid phosphate solution and metal ions are released into the solution. The aquoions formed from these cations then react with phosphate anions and form a gel of metal hydrophosphates. In the last step, the saturated gel crystallizes into a ceramic. In this paper, we have proposed that the dissolution is the controlling step and developed a general dissolution model of the kinetics of formation of these ceramics. As an example, the model is used to discuss the kinetics of formation of magnesium phosphate ceramics in detail. In the second and third papers, the model has been used to develop processes to form ceramics of alumina and iron oxides. [source] Meta-analysis: randomized controlled trials of 4-L polyethylene glycol and sodium phosphate solution as bowel preparation for colonoscopyALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 2 2010R. Juluri Aliment Pharmacol Ther 2010; 32: 171,181 Summary Background, Randomized controlled trials (RCTs) comparing polyethylene glycol (PEG) with sodium phosphate (NaP) are inconsistent. Aim, To compare the efficacy of and tolerance to PEG vs. NaP for bowel preparation. Methods, We used MEDLINE and EMBASE to identify English-language RCTs published between 1990 and 2008 comparing 4-L PEG with two 45 mL doses of NaP in adults undergoing elective colonoscopy. We calculated the pooled odds ratios (ORs) for preparation quality and proportion of subjects completing the preparation. Results, From 18 trials (n = 2792), subjects receiving NaP were more likely to have an excellent or good quality preparation than those receiving PEG (82% vs. 77%; OR = 1.43; 95% CI, 1.01,2.00). Among a subgroup of 10 trials in which prep quality was reported in greater detail, there were no differences in the proportions of excellent, good, fair or poor preparation quality. Among nine trials that assessed preparation completion rates, patients receiving NaP were more likely to complete the preparation than patients receiving 4-L PEG (3.9% vs. 9.8% respectively did not complete the preparation; OR = 0.40; CI, 0.17,0.88). Conclusion, Among 18 head-to-head RCTs of NaP vs. 4-L PEG, NaP was more likely to be completed and to result in an excellent or good quality preparation. [source] Hydrogenated castor oil nanoparticles as carriers for the subcutaneous administration of tilmicosin: in vitro and in vivo studiesJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 2 2009C. HAN Tilmicosin-loaded solid lipid nanoparticles (SLN) were prepared with hydrogenated castor oil (HCO) by o/w emulsion,solvent evaporation technique. The nanoparticle diameters, surface charges, drug loadings and encapsulation efficiencies of different formulations were 90,230 nm, ,6.5,,12.5 mV, 40.3,59.2% and 5.7,11.7% (w/w), respectively. In vitro release studies of the tilmicosin-loaded nanoparticles showed a sustained release and the released tilmicosin had the same antibacterial activity as that of the free drug. Pharmacokinetics study after subcutaneous administration to Balb/c mice demonstrated that a single dose of tilmicosin-loaded nanoparticles resulted in sustained serum drug levels (>0.1 ,g/mL) for 8 days, as compared with only 5 h for the same amount of tilmicosin phosphate solution. The time to maximum concentration (Tmax), half-life of absorption (T½ ab) and half-life of elimination (T½ el) of tilmicosin-loaded nanoparticles were much longer than those of tilmicosin phosphate solution. Tissue section showed that drug-loaded nanoparticles caused no inflammation at the injection site. Cytotoxicity study in cell culture and acute toxicity test in mice demonstrated that the nanoparticles had little or no toxicity. The results of this exploratory study suggest that the HCO,SLN could be a useful system for the delivery of tilmicosin by subcutaneous administration. [source] A validated enantiospecific method for determination and purity assay of clopridogrelCHIRALITY, Issue 10 2009Katarina Nikolic Abstract A new and accurate HPLC method using ,-cyclodextrin chemically bonded to spherical silica particles as chiral stationary phase (CSP) was developed and validated for determination of S -clopidogrel and its impurities R -enantiomer and S -acid as a hydrolytic product. The effects of acetonitrile and methanol content in the mobile phase and temperature on the resolution and retention of enantiomers were investigated. A satisfactory resolution of S -clopidogrel active form and its impurities was achieved on ChiraDex® column (5 ,m, 4 × 250 mm) at a flow rate of 1.0 ml/min and 17°C using acetonitrile, methanol and 0.01 M potassium dihydrogen phosphate solution (15:5:80 v/v/v) as mobile phase. The detection wavelength was set at 220 nm. The method was validated in terms of accuracy, precision, linearity, and robustness. The limit of detection for R- enantiomer and S -acid were 0.75 and 0.09 ,g/ml, respectively, injection volume being 20 ,l. Finally, the molecular modeling of the inclusion complexes between the analytes and ,-cyclodextrin was performed to investigate the mechanism of the enantiorecognition and to study the quantitative structure,retention relationships. Chirality, 2009. © 2008 Wiley-Liss, Inc. [source] | ||||||||||||||||