New organic microspheres for use in enantiomer separations by high-performance liquid chromatography

Monosized nonporous resin particles were prepared in aqueous medium by polymerisation of urea with formaldehyde in the presence of soluble Fe(III) hydrolysis polymers. Measurements of the geometrical parameters showed that the material particle size distribution was in the range 2.5-3.5 mu m (average particle diameter 2.99 mu m with standard deviation 0.49), and had a sphericity index of 0.851. Particle pore-size was determined by gel permeation chromatography. The microspheres exhibited exceptional mechanical strength, chemical stability in the pH range between 1-13, and low tendency toward swelling in the solvents commonly used in liquid chromatography. The synthesis of a chiral urea-formaldehyde based resin for the enantiomer separation of underivatized phenylalanine by ligand exchange chromatography is reported.