Preparation of polymer monoliths that exhibit size exclusion properties for proteins and peptides

Protein-resistant poly(ethylene glycol methyl ether acrylate-co-polyethylene glycol diacrylate) monoliths were prepared in 150 microm i.d. capillaries using novel binary porogenic solvents consisting of ethyl ether and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) or PPO-PEO-PPO copolymer with molecular weights (MWs) from 2700 to 5800. The effects of the MWs and concentrations of these surfactants in the porogenic solvent mixture on the pore properties of the resultant monoliths were investigated. Several of the monoliths showed improvements in protein and peptide separations over an extended MW range compared to monoliths synthesized using non-surfactant porogens (i.e., low MW organic liquids). The pore size distributions were examined using inverse size-exclusion chromatography (ISEC) of a select series of proteins and peptides covering a wide MW range. It was found that the best monolith had relatively large fractions of micropores (<2 nm, 11.9%) and mesopores in the range from 2.8 to 15.7 nm (8.5%), which are important for size-exclusion separation of peptides and proteins, respectively. The new monoliths possessed high mechanical rigidity that enabled them to withstand pressures up to approximately 4000 psi.