ИСТИНА

Increasing selectivity of the anion exchangers based on styrene and divinylbenzene copolymer (PS-DVB) is an important task of modern ion chromatography (IC). It is known that creation of hyperbranched anion exchange layers on the surface of the polymer matrix by repeating the alkylation with diglycidyl ethers and amination with primary amines allows the obtaining of highly selective stationary phases for IC. Moreover, the selectivity increases with the number of layers with each new reaction cycle consisting of alkylation and amination. In addition to improving the selectivity, this approach also allows the increase of the efficiency due to the creation of branched hydrophilic layer covering aromatic core of the adsorbent and resulting in the elimination of non-ionic interactions of polarizable anions with the hydrophobic surface. In this work the method of covalent attachment of hyperbranched anion exchange layers on the surface of PS-DVB is proposed. This approach includes the introduction of “anchor” secondary amino groups into the polymer backbone, which are subsequently treated with 1,4-bithanediol ether and methylamine, thus increasing the number of anion exchange layers after each cycle of modification. Anion exchangers with one, two, three, four and five layers were synthesized in accordance with the proposed scheme. The chromatographic properties of the obtained anion exchangers were studied in isocratic and gradient IC mode with KOH as a mobile phase. Anion exchangers obtained after three and four modification cycles exhibit good selectivity and allow the separation of the mixture of 7 anions (fluoride, formate, chloride, propionate, nitrite, bromide, nitrate) in isocratic elution mode in less than 17 minutes. The mixture of 9 anions (fluoride, formate, chloride, bromate, nitrite, bromide, nitrate, sulfate, phosphate) can be resolved with anion exchanger after 5 cycles of modification in the gradient mode in less than 20 minutes.