Application of neutral hydrophobic hypercrosslinked polystyrene to the separation of inorganic anions by ion chromatography

Neutral hydrophobic hypercrosslinked polystyrene was shown to exhibit anion-exchange properties in the pH range 2.6-4.3 that can be attributed to the presence of protonated carbonyls in the framework of the polymer. This resin does not contain any other heteroatoms, except oxygen, responsible for the occurrence of positive charge at the surface. The anion-exchange selectivity of MN-200 and monosized spherical hypercrosslinked polystyrene to inorganic anions with diluted perchloric, nitric and sulfuric acid solutions as eluent was studied and the selectivity was found to be different from that observed for the common anion-exchangers. The main features of hypercrosslinked polystyrene are weak retention of sulphate and comparatively strong retention of nitrite that can be useful in practical ion chromatography. The influence of column temperature on the retention was investigated. Calculated adsorption heats are in the range from -2 to 19 kJ/mol. The retention mechanism of inorganic anions on neutral hypercrosslinked polystyrene includes both ion-exchange and hydrophobic interactions.