Novel Uniformly Sized Polymeric Stationary Phase with Hydrophilized Large Pores for Direct Injection HPLC Determination of Drugs in Biological Fluids

Novel separation media for the direct injection of complex samples have been prepared from porous 10 Rm uniformly sized poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads. The simple hydrolysis of all epoxide groups produces beads with separation characteristics similar to those of some restricted access media. The use of a novel size-specific modification of porous materials provides separation media with even better chromatographic properties. In this approach, hydrolysis of the epoxide groups to diols can be carried out exclusively within the large pores of the medium through the use of a polymeric catalyst. The epoxide groups remaining in the small pores after hydrophilization of the large pores were then transformed either to hydrophobic C18 or phenyl groups, or to more polar diethylamino groups. Due to the size specific characteristics of the modification process used in the preparation of the beads which renders the large pores hydrophilic, no protein interaction with the surface of the pores was observed, the protein recovery was high, and the retention times of proteins and of a non-retained probe was similar. Examples of separations of drugs from plasma document the good efficiency and excellent selectivity of columns packed with the novel separation medium.