Вплив Замісників Та Характеру Середовища На Аналітичні Властивості Асоціатів Ксантенових Барвників З Полігексаметиленгуанідиній Хлоридом

Abstract

The interaction of 5 anionic xanthene dyes -9-R-2,3,7-trihydroxy-6-fluorones (ТОF) with cationic polyelectrolyte (PE) -polyhexamethyleneguanidine chloride (PHMG) has been studied by the optical spectroscopy in a concentration range where PHMG has a polyelectrolyte effect. Hammet σ-constants were calculated. The correlations between structure of ТОF and shift of protolytic equilibrium in aqueous-polyelectrolyte solutions were established. Influence of рН, concentration of the ethanol, components ratio in the system PHMG-TOF on the character of the interaction of cationic PE with ТОF and value of the analytical signal were studied based on absorption spectra. The results were compared to those obtained in water solutions.Keywords: trioxyfluorone; spectrophotometry; polyhexamethyleneguanidine chloride; polyelectrolyte; ionisation constant; aggregation.Introduction. The application of dyes is frequently connected with the definition of PE [1][2][3][4][5][6][7]. 9-R-2,3,7-Triohydroxy-6-fluorones are the most widely studied and used. The degree of PE influence on ionic equilibriums in the dye solutions depends on numerous factors involved in the process of PE-dye interaction. The effect is caused by capability of PE to change property of the substances in solubilized condition that is connected with the change of medium properties in a microenvironment [8; 9]. The solubilized substance passes from aqueous to aqueous-polyelectrolyte microphase. Thus the competitive interactions between polymeric molecules and dye, solvent and components of the system are possible. The number of trapped ions of dye depends on the number and conformation of PE molecules in the solution [10; 13]. The formation of assosiates «PE-dye» is possible by means of a hydrogen bridging, electrostatic and hydrophobic interactions and depends on the concentration ratio of the components. The change of chemical-analytical properties of dyes in the presence of PE was described earlier: phenylfluorone with a nonionic PE poly(vinylpirrolidone) [11], bromphenol red and chlorphenol red with PHMG [8; 9]. The purpose of the present work is to study the optical, protolytic properties, as well as specifics of associate formation between ТОF with various substituents in 9 position of xanthene core and cationic PE -PHMG (М r ≈1,0×10 4 and 6,4×10 3 ) in aqueous and aqueous-alcoholic solutions. Experimental Materials and methods. Structural formulae of ТОF ( fig. 1) are shown in a table 1. Starting solutions of PhF and SF C = 1×10 -3 mol/L were prepared on the day of the experiment by dissolving the sample in 25 ml of twice-distilled water with addition of several drops of concentrated NaOH solution. Initial alcoholic solutions of o-NPhF, DSPhF and NF were prepared according to recommendations [12]: 1 ml HCl (6 mol/L) and 80-85 ml of 96% ethanol were added to the sample of dye and carefully heated until