Enantioselective determination of modafinil in pharmaceutical formulations by capillary electrophoresis, and computational calculation of their inclusion complexes

A fast capillary electrophoretic method is described for the separation and determination of the enantiomers of the novel wake-promoting agent, modafinil. Several parameters affecting the separation were studied, including the type and concentration of chiral selector, buffer pH, buffer concentration, voltage and temperature. Good chiral separation of the racemic mixture was achieved in less than 5 min with resolution factor Rs?=?2.51, using a bare fused-silica capillary and a background electrolyte (BGE) of 25 mM H₃PO₄?1 M tris solution; pH 8.0; containing 30 mg mL^?1 of sulfated-β-cyclodextrin (S-β-CD). The separation was carried out in normal polarity mode at 25 ^?C, 18 kV and using hydrostatic injection. Acceptable validation criteria for selectivity, linearity, precision, and accuracy were included. The developed method was successfully applied to the assay of enantiomers of modafinil in pharmaceutical formulations. The computational calculations for the enantiomeric inclusion complexes rationalized the reasons for the different migration times between the modafinil enantiomers.     

Elliptically polarized breather in the nonintegrable problem of laser radiation propagation through an isotropic gyrotropic nonlinear medium

A particular analytical solution to the nonintegrable problem of plane electromagnetic wave propagation through an isotropic gyrotropic nonlinear medium is found in the form of elliptically polarized breather. The intensity ratio for the circularly polarized components of this wave, which remains constant during propagation, can be used to determine the ratio of local and nonlocal nonlinear susceptibilities describing the Kerr nonlinearity and its spatial dispersion.     

Internal rotation and intramolecular hydrogen bonding in thiosalicylamide: gas phase electron diffraction study supported by quantum chemical calculations

Structural Chemistry - The molecular structure of thiosalicylamide (2-hydroxythiobenzamide) was investigated in the gas phase at 401 K by means of gas electron diffraction (GED) combined...     

Mixed iodonium-, phosphonium-, arsonium-, sulfoniumdiazonium ylides in reactions with nucleophiles

Russian Chemical Bulletin - The reactions of mixed ylides containing a diazonium fragment and an "onium" group of different nature with nucleophiles were studied. In the...     

Kinetic and analytical study on precipitation reactions with110AgNO3 of some di (β-chloroethyl) amine derivates and hydrochlorides with esters of N-(p-aminobenzoyl)-L-aspartic acid as carriers from dimethylformamide-water solution

The kinetics of precipitation reactions with¹¹⁰AgNO₃ of some di (β-chlorethyl) amine derivates and hydrochlorides with esters of N-(p-aminobenzoyl)-L-aspartic acid as carriers in dimethylformamide-water mixture, were studied. The rate constants of these reactions were of the order of 10^?4 1 · mol^?1 · min^?1. The concentrations of the corresponding hydrochloride solutions were measured by radiometric titration with¹¹⁰AgNO₃ solution of given concentration.