ИСТИНА

Nowadays, the development of more selective anion exchangers attracts a lot of attention due to the permanently increasing complexity of analytical tasks solved by ion chromatography, which require determination of a wide range of organic anions. Among the known polymer-based stationary phases for ion chromatography, hyperbranched anion exchangers are of great interest because of their very high selectivity and possibility of its variation during the synthesis. In literature such phases are mainly presented as anion exchangers with electrostatically attached functional layers formed by consecutive repeating of alkylation with 1,4-butanediol diglycidyl ether and amination with methylamine. Earlier we found that insertion of glycine into covalently bonded hyperbranched functional layer resulted in significant selectivity improvement toward weakly retained organic acids which made us expect alternative and improved selectivity when using other types of primary amines in hyperbranched layers. The aim of the present work was to establish the influence of amine substituent structure on selectivity towards weakly retained organic acids, such as quinic, gluconic, glycolic, shikimic, acetic, lactic, formic, and galacturonic. Hydrophilicity and charge of hyperbranched functional layer was varied by means of using amino acids, amino sulfonic acids, and amino alcohols in the internal part of the layer. As a result, three different types of stationary phases were synthesized and compared for evaluating the selectivity shifts for organic anions. The obtained anion exchangers were investigated by using 4 mM KOH as eluent and retention mechanisms for weakly retained organic acids were evaluated. The most selective stationary phases provided the separation of up to 25 anions in gradient elution mode including standard inorganic anions, anions of mono- and poly-valent organic acids, and oxyhalides. Revealed correlations between the structure of amine substituent in functional layers and selectivity of anion exchangers allowed us to find the way of constructing anion exchangers with desired properties for solving particular analytical tasks.