Voltammetric determination of α-tocopherol in the presence of surfactants

As established, α-tocopherol is electrochemically active on glassy carbon electrode in the available range of anodic potentials in acetonitrile and its aqueous mixtures. However, an increase in the water percentage up to 50% and beyond leads to a substantial decrease and then the total disappearance of the analytical signal. A scheme of electrode reaction responsible for the signal formation is proposed. The effect of surfactants on the oxidation of α-tocopherol in aqueous acetonitrile is estimated. As found, surfactants (N-dodecylpyridinium bromide, Triton X-100 and N-cetylpyridinium bromide) enhance the current of α-tocopherol oxidation. The surfactants reduce the detection limit and extend the analytical range. Analytical methods for the voltammetric quantification of α-tocopherol in drugs in the presence of surfactants are elaborated and may be recommended for the control of pharmaceuticals.     

Generalization of theorems of Szász and Ruscheweyh on exact bounds for derivatives of analytic functions

Let Ω and Π be two domains in the extended complex plane equipped by the Poincaré metric. In this paper we obtain analogs of Schwarz-Pick type inequalities in the class A(Ω, gH) = {f: Ω → Π} of functions locally holomorphic in Ω; for the domain Ω we consider the exterior of the unit disk and the upper half-plane. The obtained results generalize the well-known theorems of Szász and Ruscheweyh about the exact estimates of derivatives of analytic functions defined on the disk |z| < 1.     

Investigation of the Spectral Line Intensities of the ν9 Band of the Trans-Conformer of Ethylene

Russian Physics Journal - The intensities of 740 vibrational-rotational lines of the ν9 fundamental band in the IR spectrum of the trans-C2H2D2 molecule are first analyzed. The...     

Cyclic Voltammetry of Retinol in Surfactant Media and Its Application for the Analysis of Real Samples

Retinol is irreversibly oxidized at 790 mV in water 0.1 M LiClO₄ that corresponds to formation of retinal. Effect of surfactant on voltammetric characteristics of retinol oxidation has been evaluated. The calibration graph was linear in the range 29.4–980 µM of retinol with detection limit of 15 µM in presence of 1.1×10^?4 M of sodium dodecyl sulfate. Application of surfactant media leads to decrease of detection limit, enlargement of analytical range for retinol determination and permits analyze retinol in water media. Simple, express and reliable voltammetric approach for determination of retinol in real samples using surfactant media have been developed.     

On the Pseudopotential Model of Interacting Particle and Electrical Conductivity of Fully Ionized Plasma

The value of the Coulomb logarithm, as a determining factor in investigations on the kinetic properties of plasma, is calculated on the basis of effective potentials of particle interactions of dense semiclassical plasma. The expression for the electrical conductivity of dense semiclassical nonideal plasma, which is compared with the results of other authors, is calculated using the Coulomb logarithm. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Study of the ν2 + ν10 Hybrid Band of the Trans-C2H2D2 Molecule

Russian Physics Journal - The ν2 + ν10 (Bu) hybrid band of the trans-C2H2D2 molecule in the region 2100–2300 cm–1 is studied for the first time. The spectrum has been analyzed...