Application of Sulphonated Styrene and Divinylbenzene Copolymers with Various Degrees of Crosslinking to Ion Exclusion Chromatography

The chromatographic retention of neutral polar compounds (alcohols, ketones, carboxylic acids, carbohydrates, and sweeteners) and compounds in the ionized form (mono- and dibasic organic acids) on cation exchange columns packed with sulfonated poly(styrene-divinylbenzene) having crosslinking degrees of 8% (Nautilus-IE) and 10% (Sevko AA) is studied in ion exclusion chromatography. Using 5 mM sulfuric acid, the retention parameters of the compounds are determined and new patterns are obtained, clarifying the mechanism of retention of organic acids in ion-exclusion chromatography. It is found that the retention of all the studied compounds (logk') is directly proportional to hydrophobicity values (log P_exp). In this case, the electrostatic repulsion of organic acids from the sulfo groups of the cation exchanger shifts the log k'–log P_exp dependences by a constant value, proportional to the number of carboxyl groups. A possibility of using the Sevko AA column not only for amino acid analysis, but also for the determination of organic acids and alcohols in complex samples by ion exclusion chromatography with spectrophotometric and refractometric detection is shown.