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  • Author or Editor: K. Murthy x
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Abstract  

Isotope exchange behavior of bis(resacetophenone oxime)copper(II) complex with copper(II) in tri-n-butyl-phosphate and methanol medium has been studied. The studies were carried out at different temperatures varying the concentration of both metal ion and complex. The results show that the complex is labile in the kinetic sense. Increase in temperature increases the isotope exchange rate. The increase in concentration also results in enhancement of the rate of reaction.

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Thermal studies on CuCr2O4 spinel indicated the phase present above 870 K to be cubic CuCr2O4. However, when the substance was quenched from 1023 K, 1173 K, 1273 K and 1473 K, only the tetragonal phase of CuCr2O4 was obtained. This is because the first-order, diffusionless, tetragonal to cubic phase transition at 865 K occurs reversibly at a very fast rate. Thec/a ratio for CuCr2O4 present in the various quenched samples did not change when the quenching temperature was raised. A strong preference of the Cr3+ ion for the B site prevents it from interchanging sites with Cu2+ ions, thus keeping the lattice parametersc anda unchanged.

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Abstract  

This paper compares the urinary excretion levels of Th obtained in bio-assay monitoring using the neutron activation technique with those predicted by applying the ICRP metabolic model to the measured Th activity in chest and total body of a group of Thorium plant workers. The results indicated much lower urinary Th excretion as compared to what was expected on the basis of the ICRP model. Lower urinary excretion in occupational subjects is explained in terms of negligible contribution of skeleton and soft tissue to the activity excreted in urine. It is suggested that the existing model should be modified to enable it to be applicable to the bio-assay monitoring of occupational workers.

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Abstract  

A composite mixture of zirconium molybdate and zirconium tungstate was prepared and studied for the sorption of cesium and strontium as a function of nitric acid, metal ion concentration, time and temperature. The distribution coefficient (Kd) of 7000 ml/g (~90% sorption) and 70 ml/g (~20% sorption) was obtained for the sorption of cesium and strontium in 0.1M nitric acid, respectively. Experimental sorption capacity, b for cesium was found to be 50 mg/g from 0.1M HNO3 and 30 mg/g for strontium from 0.001M nitric acid. The sorption of strontium on the sorbent was accompanied by the absorption of heat but the sorption of Cs+ results in the liberation of heat. Column studies were conducted by following a breakthrough (BT) curve of cesium and strontium up to C/C0=1 and the results are reported.

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Linaclotide, a first-in-class guanylate cyclase-C agonist, was recently approved by US Food and Drug Administration (FDA) as a promising pharmacotherapy for the management of constipation-predominant irritable bowel syndrome (IBS). In this communication, we present a novel stability-indicating reverse-phase high-performance liquid chromatography (RP-HPLC) method for the quantitative determination of linaclotide along with its degradation products. During the International Conference on Harmonization (ICH) prescribed stress study, linaclotide was found susceptible to degrade under hydrolytic (acid and base) and oxidative (peroxide) conditions. The separation of the degradants from the analyte was achieved on a Zorbax Eclipse XDB C8 Column (250 mm × 4.6 mm, 5 μm) using 0.01 N potassium dihydrogen orthophosphate buffer and acetonitrile (80:20 v/v) as mobile phase at a flow rate of 1.00 mL min−1 at column temperature of 40 °C. The detection of the column effluents was realized on a photodiode array detector set at 220 nm. Under the above optimal condition, the method was validated with respect to specificity, linearity, range, precision, robustness, and sensitivity in compliance to the regulatory requirements.

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