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Novel polymer-based anion exchangers with covalently-bonded functional layers of quaternized polyethyleneimine for ion chromatography

Shchukina, O.I., Zatirakha, A.V., Uzhel, A.S., Smolenkov, A.D., Shpigun, O.A.
Analytica chimica acta 2017
acetates, alkylation, analytical chemistry, anion exchange, anions, bromates, bromides, butyrates, chlorates, chlorides, chromates, epoxides, fluorine, formates, hydrophilicity, iodides, ion exchange chromatography, nitrates, nitrites, oxalates, phosphates, propionic acid, sulfates, thiocyanates, thiosulfates
For the first time novel pellicular anion exchangers with functional layers of quaternized branched polyethyleneimine (PEI) covalently bonded to the surface of aminated poly(styrene-divinylbenzene) (PS-DVB) with 1,4-butanediol diglycidyl ether (1,4-BDDGE) as a linker are obtained and studied. The proposed method of synthesis includes the alkylation of PS-DVB substrate containing secondary aminogroups with 1,4-BDDGE followed by amination with branched PEI containing primary, secondary, and tertiary amino groups. Quaternization of amino groups of PEI required for increasing ion-exchange capacity of the stationary phase is provided with two epoxides – glycidol and 1,4-BDDGE, which results in the considerable variations of ion-exchange selectivity. Chromatographic properties of the obtained anion exchangers are evaluated using various model mixtures of anions (F-, HCOO-, CH3COO-, C2H5COO-, Cl-, BrO3-, NO2-, Br-, NO3-, ClO3-, S2O32-, C2O42-, CrO42-, SO42-, PO43-, I-, SCN-) in hydroxide and carbonate/bicarbonte eluents. All anion exchangers show better selectivity toward the anions of weakly retained organic acids (acetate, formate, propionate) as compared with previously reported chemically derivatized anion exchangers with monomeric functional sites in the ion-exchange layer. In terms of separation abilities, novel anion exchangers with covalently-bonded PEI are not inferior to some commercial columns with grafted polymeric anion exchange layer. Anion exchanger quaternized with more hydrophilic glycidol packed in 10-cm long column enables the separation of 16 anions including weakly retained and highly retained polarizable ones in one run within 26 minutes using gradient elution. Column efficiencies for both anion exchangers with quaternized PEI are up to 32000 N/m and 37000 N/m in case of hydroxide and carbonate eluent, respectively, which is comparable with the values demonstrated by commercially available columns of related chemistry.