Sulfonated acrylamide copolymers as pseudo-stationary phases in electrokinetic chromatography

Sulfonated copolymers were synthesized, characterized and used as separation media in electrokinetic chromatography. The polymers used were synthesized from AMPS (2-acrylamido-2-methyl-1-propanesulfonic acid) and LMAm (lauryl methacrylamide) in different mole ratios (from 100:0 to 60:40). Electrophoretic mobilities and methylene selectivities were calculated, which showed the expected correlation with the monomer ratios. The chemical selectivities for the separation of nine solutes by the copolymers were compared with that of sodium lauryl sulfate micelles, showing significant differences. No significant difference in chemical selectivities was observed for copolymers with different monomer ratios. No significant change of hydrophobic microdomain of copolymers was found in background buffers with different ionic strength values, based on the investigation of the retention factors, methylene selectivities and polymer effective mobilities. No change of hydrophobic microdomain of the copolymer solutions was found at copolymer concentrations from 0.17 to 3% (w/v), however, plots of k′ versus polymer concentration suggested a different copolymer phase at lower concentrations (from 0 to 0.1%, w/v) from that at higher concentrations (from 0.17 to 3%, w/v). The copolymer with AMPS–LMAm (80:20) could be chosen as optimum copolymer as far as the methylene selectivity, peak symmetry and polymer mobility were concerned.