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Abstract  

The conductivities of binary mixtures of glycerine and water were measured at 20C by means of a transient method. The equation describing the correlation between concentration and thermal conductivity was determined. The equation can be used for determining concentrations in mixtures. The results show that (1) the error in the determination of the molar concentration of water in mixtures is less than 1%, (2) the time of measurement is 1 s, (3) this method can be used for on-line analysis in production control.

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Summary

Ezetimibe is the first in a new class of antihypercholesterolemic drugs. Since it has not long been available on the market, many of its properties may still be revealed. Analytical methods for its determination are scarce, especially regarding serum samples. A simple, fast, and effective high-performance liquid chromatography-ultraviolet (HPLC-UV) method for the determination of ezetimibe concentration in human serum has therefore been developed. Three mobile phases were analysed, and original modifications to the concentration and flow parameters were made. Of five potential internal standards (IS), only nitrendipine was found to be suitable. The analytical wavelength was chosen based on the absorption spectrum of ezetimibe in the mobile phase. Finally, an extraction analysis was performed using two different solvents, and the extrahent volume was optimised. The final method developed was as follows. Single extraction of 1 mL serum sample, spiked with IS, was performed using 10 mL of methyl-t-butyl ether. Separation was obtained at ambient temperature on a Waters C18 Symmetry Shield (4.6 mm × 250 mm, 5 μm) column. The isocratic mobile phase was composed of acetonitrile and 0.1 M ammonium acetate aqueous solution 55:45 (v/v), set at flow rate of 0.75 mL min−1. Ezetimibe was detected at a wavelength of 232 nm after 5.49 min, and the IS was detected at 8.05 min. The developed method has been validated according to ICH standards. It was found to be specific, precise, accurate and linear over the range 10–800 ng mL−1 with R 2 > 0.998, and detection and quantification limits of 4.60 ng mL−1 and 13.94 ng mL−1, respectively. The method has been applied to clinical serum samples. The developed technique allowed for successful in vivo assessment of ezetimibe concentrations in samples obtained from hypercholesterolemia patients who are chronically receiving the drug.

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Abstract  

Surface seawater and water vapor about 10 m above the sea level were collected in the Pacific and Indian Oceans during the expedition of KH-96-5 to examine tritium concentrations in open sea. The tritium concentration in the water vapor was one order of magnitude higher than that in the surface seawater, attributed to downward movement of naturally occurring tritium from stratosphere to troposphere.

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] examined influence of temperatures on degradation of wooden materials by analysis of selected thermal degradation products (formaldehyde, acetaldehyde, vanillin, 2-furaldehyde). From the presented results, the concentration investigated thermal

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sufficient to maintain an oxygen concentration with 20.95% by volume in the area affected by fire. The result of this fact is that most internal fires are in an atmosphere with a reduced oxygen concentration. Final products of the oxidation of carbon

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Acta Chromatographica
Authors: Samiuela Lee, Christa E. Nath, Ben W. R. Balzer, Craig R. Lewis, Toby N. Trahair, Antoinette C. Anazodo, and Peter J. Shaw

proportionality with respect to maximal plasma concentrations and area under the plasma concentration–time curve was demonstrated across a dose range of 300 to 900 mg twice daily, with 600-mg twice daily being recommended for further phase 2 studies on the basis

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, thermodynamic studies at low concentration, of less than 0.05 mol kg −1 , are scarce; in the literature, data are found for partial molar volumes at molar concentrations above 0.05 mol L −1 [ 6 ] and it is only possible to find data of enthalpies of solution at

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Abstract  

A method is proposed by which the significance of the differences between trace element concentrations of sample and control can be estimated without detailed knowledge of the distribution in the total population. Both sample and control are cut in half and the trace element concentrations of all four pieces are determined. The concentration values of the two halves of each sample are compared with each other and so are the concentration values of the two samples. This cross-comparison is essentially the application of Student's t-test to the smallest possible number of data. The calculation is reduced to a simple formula, and tables of confidence limits are not needed. The implications of lack of general background knowledge are discussed. Since it cannot always be known whether a certain trace element follows a normal or log-normal distribution pattern, or whether simultaneously determined concentrations of several trace elements are correlated with each other, the most cautious estimate of the significance is recommended.

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Abstract  

Rice plants were grown in an experimental field and separated at harvest into different components, including polished rice, rice bran, hull, straw and root. The distribution of chlorine in these components was determined by instrumental neutron activation analysis. The concentration of chlorine in the roots was the highest (4800 mg·kg−1 dry wt.) and that in the polished rice was the lowest (140 mg·kg−1 dry wt.) among the plant components. The content of chlorine in the polished rice was about 2% of the entire plant, and the rest was present in the inedible portions; about 75% of the total chlorine content was in the straw. The percentage of chlorine removed from the surface soil layer to the above ground biomass of the rice plants was calculated as 5% every year. The chlorine concentrations in leaf blades of different positions collected from four growing stages varied by more than one order of magnitude, and were well correlated with the sum concentrations of major cations (potassium + calcium + magnesium). This may be attributed to the fact that the translocation rate of chlorine among the leaf blades with age depends on the concentrations of the major cations.

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Acta Chromatographica
Authors: Feng Wu, Xiuli Zhao, Shumin Wang, Hui Zhou, Shaojie Guo, Siyang Ni, Bo Yang, Lihua Zhang, and Xinde Xu

[ 1 ]. Lutein is found in a number of human tissues but the highest concentration of these carotenoids (0.1–1 mM) is found in the human retina [ 2 ]. In the human eye, lutein and zeaxanthin are specifically located at the center of the retina

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