Renkevich A. Broadening of analytical possibilities of the micellar thin-layer chromatography for determination of bioactive substances

The manuscript is devoted to investigations of the influence of micellar mobile phase (MMP) composition and chromatographic parameters on the separation process and analyte spot form in micellar TLC. The dependence of physicochemical parameters (density, surface tension) of MMP on their composition and its influence on the separation of analytes of various structures was investigated. Increase of the modifier volume fraction results in decrease of surface tension and simultaneous increase of viscosity of MMP; the influence of organic modifier on MMP viscosity is much stronger than influence of surfactants. The dependence of stream constant (χ) on transmissibility constant (γ/η) was studied. It was demonstrated, that χ depends on both physicochemical parameters of MMP. Based on the investigations of the χ value dependence on chromatographic tank saturation, it was scientifically grounded that gaseous phase does not influence the chromatographic process in micellar TLC. It was demonstrated, that the organic modifiers with equal number of carbon atoms (2-propanol and propionic acid) influence physicochemical characteristics of MMP and have equal effect on both viscosity and surface tension of MMP as well as separation selectivity of the coumarin derivatives. The assay methods for determination of 4-aminobutyric acid as impurity or active component in different drugs was developed and validated. It was demonstrated that usage of MMP (5 mmol/l Brij 35 aqueous solution adjusted to pH 2.0 by hydrochloric acid) allows to determine 4-aminobutyric acid during 30 min including 20 min of chromatographic separation stage. The proposed methods are alternative to the existing 4-aminobutyric acid assay method – reversed-phase high-performance liquid chromatography and volumetric titration method with use of formalin.