A hyperbranched anion exchanger obtained by carboxylate surface modified polymer substrate for ion chromatography

A surface-carboxylated polymer substrate-based hyperbranched anion exchanger has been described for ion chromatography (IC). It is prepared by grafting maleic anhydride onto porous polystyrene-divinylbenzene (PS-DVB) microspheres, then hydrolyzed to generate carboxylate groups being anchor points for electrostatic attachment of positively hyperbranched polymer obtained by cyclic reaction of diepoxides and amines. The obtained anion exchanger shows high hydrophilicity and good chromatographic performance, as demonstrated by the separation of common inorganic anions, including polarizable anions, disinfection byproducts and organic acids. High efficiency and good peak shape were achieved, as indicated by the theoretical plate counts of 45,000/m, 51,000/m and asymmetry factors of 1.12, 1.08 for nitrite and bromide, respectively. A desirable feature of such carboxylated groups-based anion exchanger is elimination of possible bleed of sulfate encountered in common sulfonated-based ones, avoiding sulfate blank in the case of the analysis of trace anions in pure water.