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...