Search results for "Solution"

ChemInform Abstract: Solution Synthesis of Nanoparticular Binary Transition Metal Antimonides.

2011

The transition metal antimonides MSb with M: Co, Ni, and Zn and Cu2Sb with particle sizes ranging from 20 to 60 nm are prepared using presynthesized antimony nanoparticles and activated metal nanoparticles as precursors.

Book Review: Ions in Solution: Basic Principles of Chemical Interactions. By J. Burgess

1989

ChemInform Abstract: Solution Synthesis of a New Thermoelectric Zn1+xSb Nanophase and Its Structure Determination Using Automated Electron Diffractio…

2010

Thermoelectric nanoparticles of the nominal composition Zn4Sb3 are prepared by heating Sb nanoparticles with a 9-fold excess of Zn particles (synthesized by reaction of SbCl3 or ZnCl2 with Li[Et3BH] in THF at room temperature, and about 65 °C, respectively) in trioctylamine at about 300 °C for 225 min.

Nondestructive full-field imaging XANES-PEEM analysis of cosmic grains

2006

For chemical analysis of submicron particles, mass spectrometric methods have the disadvantage of being destructive. Thus, a nondestructive elemental and chemical mapping with a high spatial resolution prior to mass analysis is extremely valuable to precharacterize the sample. Here, first results are presented of combined XANES (x-ray absorption near-edge structure) and PEEM (photoemission electron microscopy) measurements on a cosmic grain fraction from the Murchison meteorite. This nondestructive full-field imaging method is well suited for a quantitative analysis and for a preselection prior to detailed mass spectrometric investigations with isotopic resolution/selectivity. A spectral un…

Electrochemical characterization of solid state reaction kinetics using voltammetry of microparticles. Application to thermal decomposition of iron c…

2011

The voltammetry of microparticles is applied to characterize the electrocatalytic ability of solids towards selected electrochemical processes. The variation of catalytic currents under fixed electrochemical conditions permits to obtain composition/time data to be fitted with solid state kinetic models. This methodology is applied to analyze the thermal decomposition of magnesiochromite ferroan and chlorite chromian standards and a South Africa iron chromite ore on the basis of the significant catalytic effect on the electrochemical oxygen evolution reaction (OER) in aqueous alkaline media at mineral-modified graphite electrodes. Measurement of the time variation of catalytic current for OE…

Study of solid state kinetics using voltammetry of immobilized particles. Application to tetragonal to monoclinic transition in nanoparticulate zirco…

2012

Abstract The voltammetry of immobilized particles methodology is applied to study solid state reaction kinetics on the basis of the electrocatalytic ability of solids toward selected electrochemical processes. Measurement of the time variation of catalytic current for oxygen evolution reaction in aqueous alkaline media provides a direct estimate of fractional conversion of the reactant in the course of the reaction for testing different reaction kinetic models. This methodology is applied to analyze the formation of monoclinic zirconia and praseodymia-doped zirconia from tetragonal precursors. Discrimination between competing and successive reactions mechanisms is obtained for reactions inv…

A system for rapid radiochemical separations from aqueous solutions

1969

Abstract For the study of short-lived fission products, an automatic system has been developed that allows to irradiate aqueous solutions sealed in polystyrene capsules, to separate chemically the radioactive products formed, and to start counting, all within a few seconds. Irradiations are performed in a pneumatic tube system installed in a horizontal beam hole of a reactor. The capsule is projected into a separation apparatus where it breaks by impact. Its content is then sucked through a thin reactive layer that takes up the desired product. The whole sequence of irradiation, transportation, chemical separation, and counting is controlled by automatic timers. The adaption of this techniq…

In vitro prediction of in vivo absorption of ibuprofen from suspensions through rational choice of dissolution conditions

2020

Two ibuprofen suspension formulations were investigated for their dissolution in various bicarbonate, phosphate and acetate buffers. Phosphate and acetate gave faster release than bicarbonate at comparable molarities. Nevertheless, mass transport modelling using the reversible non-equilibrium (RNE) approach enabled the calculation of phosphate molarities that gave good matches to physiological bicarbonate in terms of ibuprofen dissolution. This shows that developing surrogate buffers for bicarbonate that are devoid of the technical difficulties associated with the bicarbonate-CO2 systems is possible. In addition, the intestinal dissolution kinetics of the tested suspensions were determined …

Three simultaneous dissolution profiles on a solid pharmaceutical formulation by a FIA manifold provided with a single spectrophotometric detector.

2003

This article deals with the simultaneous determination of three dissolution profiles in the same pharmaceutical formulation. The officially proposed procedure from the pharmacopoeias is adapted to the FIA methodology to obtain the officially recommended profile or "global profile", and two "individual" profiles, corresponding to dissolution rate of two different active principles present in the formulation; both drugs have overlapped UV-vis spectra. The simultaneous determination of several profiles is based on the derivative spectra and the zero crossing mathematical procedure for the "individual" profiles of an active principle; the "global" profile of the formulation is obtained from the…

Toward Biopredictive Dissolution for Enteric Coated Dosage Forms

2016

The aim of this work was to develop a phosphate buffer based dissolution method for enteric-coated formulations with improved biopredictivity for fasted conditions. Two commercially available enteric-coated aspirin products were used as model formulations (Aspirin Protect 300 mg, and Walgreens Aspirin 325 mg). The disintegration performance of these products in a physiological 8 mM pH 6.5 bicarbonate buffer (representing the conditions in the proximal small intestine) was used as a standard to optimize the employed phosphate buffer molarity. To account for the fact that a pH and buffer molarity gradient exists along the small intestine, the introduction of such a gradient was proposed for p…