Capillary Ion Chromatography Using 18-Crown-6 Ether as Eluent Additive for the Separation of Anions

Abstract

The retention behavior of inorganic anions was investigated on a hydrophobic stationary phase dynamically modified with 18-crown-6 ether (18C6) in capillary ion chromatography. Styrene–divinylbenzene copolymeric (polystyrene) packing material was used as the hydrophobic stationary phase to retain 18C6. The eluent contained 18C6, salt and acetonitrile; 18C6 was retained on the stationary phase and the analytes anions were separated by the cations, which were trapped on the 18C6 and worked as the anion-exchange sites. The effect of eluent conditions, such as eluent cation species, acetonitrile (ACN), 18C6, and salt concentrations (in this case, potassium chloride was used), was investigated. The retention times of inorganic anions decreased with increasing concentration of ACN. In case ACN concentration was less than 4%, the retention times decreased with the passage of time. The retention time of inorganic anions increased with increasing concentrations of 18C6 and potassium chloride concentrations. By contrast, high concentration of 18C6 and chloride in eluent promotes elution of inorganic anions, and the retention time decreased. Furthermore, a contactless conductivity detector was used to replace the conventional UV detector to obtain higher sensitivity detection. Separation of inorganic anions was achieved with the eluent containing potassium hydroxide and enhanced peak intensity was observed using a suppressed contactless conductivity detection.