PHOTOMETRIC DETERMINATION OF ETHACRYNIC ACID IN DOSAGE FORMS AND BIOFLUIDS OF ATHLETES

Abstract

It was shown that ethacrynic acid (EA) with the polymethine dye astrafloxin FF (AF) forms an ionic associate (IA). Using the method of mathematical modeling, the energy efficiency of the formation of the IA is substantiated. Molecular modeling of EA-+ AF+ systems and related calculations were carried out using the “HyperChem 8.0” package for various initial options for the arrangement of counterions relative to each other (“single point” procedure). Geometrical optimization of ions was carried out using the MM+ molecular mechanics method. The resulting AIs are fairly well extracted with various aromatic hydrocarbons. The maximum extraction of IA from the aqueous phase is achieved at pH 4–12. The effect of dye concentration on the optical density of toluene extracts of ionic associates of EA with AF was studied. The extraction of IA reaches its maximum value at the concentration of the reagent (1.5–3.0) ·10–4 M. The extraction equilibrium is reached in 50–60 s. The stoichiometry of IA EA with AF was established by spectrophotometric methods of isomolar series and equilibrium shift; the ratio of components is 1:1. A scheme for the formation and extraction of IA is proposed. The conditional molar absorption coefficient of IA is 1.0·105. The graduation graph of the dependence of the optical density of the extracts on the concentration of EA is described by the equation of the straight line A = 0.010 + 0.052c in the concentration range of 0.7–45.4 μg/cm3 EC. The EA detection limit, calculated according to the 3s criterion (n = 5; P = 0.95), is 0.6 μg/cm3. A method of extraction-photometric determination of ethacrynic acid in medicinal forms and biofluids of athletes was developed.