Influence of capacity on four different sulfobetaine stationary phases

A number of covalently bonded zwitterionic stationary phases with inner quaternary amines and outer sulfonic acids in varying capacities was synthesized based on poly (styrene-DVB) particles by graft polymerization. The different spacer lengths and capacities are used as an investigative tool, for the retention behavior of the inorganic anions in ZIC and ZIC-HILIC modes. The results of variations of acetonitrile content, buffer concentration and mobile phase pH show that pharmaceuticals can be separated based on hydrophilic, hydrophobic and anion/cation-exchange interactions between the stationary phase and analyte. The pharmaceutical deferoxamine mesylate (DFOM) is a chelating agent which forms complexes with multiple charged metal ions of biological importance (Fe3+, Al3+) and other metals. We could demonstrate that the sulfobetaine exchangers are able to separate the Fe(III)-DFOM and Al(III)-DFOM complexes by IC-ICP-AES. Excess adsorption isotherms of water from acetonitrile were measured for ten zwitterionic stationary phases (eight sulfobetaine exchangers have been prepared and two commercially available stationary phases) using the minor disturbance method.