Semipermeable-surface reversed-phase media for high-performance liquid chromatography.

Polyoxyethylene was both adsorbed hydrophobically (through the use of non-ionic surfactants) and covalently bonded to reversed-phase high-performance liquid chromatographic packings, thereby establishing a semipermeable hydrophilic layer over the alkylsilane surface. This layer restricts proteins from adsorbing to the alkylsilane phase while permitting penetration and chromatographic separation of small molecules. Biological fluids containing low-molecular-weight analytes may be injected directly, without sample pretreatment or the use of micellar eluents. In the case of adsorbed coatings, surfactant loading was determined primarily by the surface area (over the reversed phase) occupied by the polyoxyethylene head group. Semipermeability of the hydrophilic layer was demonstrated by observing changes in retention of both small molecules and proteins with increasing eluent ionic strength. Coated column stability was evaluated with regard to cumulative eluent volume and repeated serum injections.