Analysis of inorganic anions by electrostatic ion chromatography using zwitterionic/cationic mixed micelles as the stationary phase

The inability to separate fluoride, phosphate and sulfate by electrostatic ion chromatography (EIC) was overcome by using: an ODS silica column coated with mixed zwitterionic-cationic surfactants as the stationary phase. The best results were obtained using the zwitterionic surfactant, 3-(N,N -dimethylmyristylammonium)-propanesulfonate (C19H41NO3S), and the cationic surfactant, myristyltrimethylammonium, CH3(CH2)(13)N+(CH3)(3), in a 10:1 molar ratio in the column coating solution. With a dilute solution of sodium tetraborate as the eluent the model analyte anions were completely separated in the following elution order: F-, HPO42-, SO42-, Cl-, NO2-, Br-, NO3-. The very early elution of phosphate and sulfate is most unusual and is unique to this system. Detection limits bet ter than 1.1 x 10(-4) mM and linear calibration plots up to 7.0 mM were obtained with a suppressed conductivity system.