Extraction and micro-determination of manganese(II) with oxine and aliquat 336

A sensitive and selective method has been developed for the micro-determination of Mn(II) by the selective extraction of the yellow Mn(II)-8-hydroxyquinolinate complex with a liquid ion-exchanger, Aliquat 336, from basic medium. The molar absorptivity of the complex is 2.2 x 10(4)1.mole(-1).cm(-1) at 420 nm and the colour system obeys Beer's law in the range 0.1-3.5 ppm Mn(II) in the final solution. The composition and stability of the complex are discussed. Potential interferents have been examined and the method is applied to analysis of standard steel and bronze samples.     

Radiochemical measurement of solubility product and thermodynamic functions for erbium trifluoride-water system

The solubility and solubility product of erbium trifluoride in aqueous solution were measured using three different techniques. The more acceptable radiometric values for the solubility and solubility product are 1.98×10^–5M and 3.5×10^–18, respectively. The values for the thermodynamic functions, H ₂₉₈ ^o , G ₂₉₈ ^o and S ₂₉₈ ^o for the dissolution of ErF₃ and the stability constant for ErF²⁺ have also been measured.     

Magnetic enhancement and magnetic reduction in binary clusters of transition metal atoms

Electronic and magnetic properties of small binary clusters containing one or two transition metal atoms are investigated using ab initio calculations with a view to explain the experimentally observed magnetic enhancement/reduction in these systems. As the present investigations do not rely on spin-orbit effects, our results reveal the enhancement or reduction in the magnetic moment to depend on two main factors; namely geometry and, most importantly, the d-band filling. The results can be used as a guide in the experimental synthesis of high density magnetic grains.     

Ethanol Washing Effect on Textural Properties of the Sodium Silicate-Derived Silica Xerogel

This study deals with the use of ethanol as washing solvent in the preparation of the silica gels from sodium silicate in order to enhance the textural properties, especially surface area. We here examined the effect of ethanol-washing on surface area, micro- and mesopore volume, and average pore size. The silica xerogels prepared from sodium silicate solution exhibited an extremely high surface area of 1139 m2/g by washing their hydrogels with ethanol. Compared to water-washed xerogels, ethanol-washed xerogels showed higher surface areas, total pore volumes, and larger average pore sizes. Unlike the surface area of water-washed xerogel, that of the ethanol-washed xerogel was not affected by the silica concentration of initial solution. This study indicates that the textural properties of sodium silicate-derived xerogels are further enhanced by using ethanol as washing solvent.     

HPLC Determination and Pharmacokinetic Study of Valdecoxib in Human Plasma

A sensitive, simple, and accurate high-performance liquid chromatographic method has been developed for determination of valdecoxib and the internal standard rofecoxib in human plasma. Protein was precipitated from plasma samples by addition of perchloric acid (HClO₄); the drug was then extracted with diethyl ether. Separation was performed on a Cosmosil C₁₈ column (150 mm × 4.6 mm i.d., 5 m particles) with ammonium acetate buffer-acetonitrile, 60:40 (v/v), containing 0.1% TEA, pH 6.5, as mobile phase. Detection and quantification were performed by UV-visible detection at 239 nm. Detection and quantification limits were 3 and 5 ng mL^–1, respectively. The linear concentration range for valdecoxib was 5–400 ng mL^–1. The validated RP HPLC method was used for determination of the pharmacokinetic data for the drug in humans.     

Quantitative Determination of Eugenol from Cinnamomum tamala Nees and Eberm. Leaf Powder and Polyherbal Formulation Using Reverse Phase Liquid Chromatography

A simple, rapid and precise reverse-phase high performance liquid chromatographic method has been developed for the quantitative determination of eugenol from the extract of dried powder of Cinnamomum tamala leaves and its polyherbal formulation. Chromatographic analysis was carried out on Zorbax C₁₈ column (150 mm × 4.6 mm, 5 μm) with a mobile phase of mixture of water, acetonitrile and methanol in the volume ratio of 50:40:10, at a flow rate of 1.0 mL min^-1. Quantitation was performed using a UV-visible detector at 210 nm. Good linearity was obtained over the ranges of 0.20–3.0 μg mL^-1 for eugenol.