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 (IC), which require simultaneous determination of organic and inorganic anions. Among the known polymer-based stationary phases for IC, 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 (1,4-BDDGE) and amination with methylamine (MA). Earlier we found that covalent attachment of hyperbranched layer formed with 1,4-BDDGE and MA to the surface of polystyrene-divinylbenzene substrate results in the preparation of anion-exchangers with very limited separation selectivity. Therefore, the purpose of the current work was to increase selectivity of covalently-bonded hyperbranched anion-exchangers. For the first time introduction of primary amines with hydrophilic and charged groups, namely, amino acids and amino sulfonic acids, into the structure of covalently-bonded hyperbranched layers is proposed. The influence of acid structure, its position in hyperbranched layer, number of acid-containing layers as well as total number of layers on selectivity of anion-exchangers is investigated. The optimal structures of hyperbranched layers providing the best separation of anions are revealed. It was found that insertion of acids into internal part of covalently-bonded hyperbranched layers results in significant selectivity improvement, especially for organic acids, in comparison with stationary phases obtained using only MA for amination. The obtained anion-exchangers are compatible with hydroxide solutions as eluents and even 10-cm long columns provide the separation of at least 20 anions in gradient elution mode including standard inorganic anions, anions of mono-, di- and tri-valent organic acids, and oxyhalides. Using 25-cm long column results in considerable increase of resolution and possibility of separating up to 25 anions. The obtained anion-exchangers can be successfully applied for solving various analytical tasks of environmental control, food and pharmaceutical industries.