Wide range of pore sizes and high compatibility with 100% aqueous phases make Bio-C18 columns ideal for high resolution mapping of peptides and separation of natural and synthetic peptides and small proteins. The specially designed surface bonding chemistry and the pore sizes allow for extended retention and selectivity for polar and hydrophilic compounds, such as peptides and amino acids. C18 monolayer formed by special bonding chemistry does not collapse in pure aqueous solution.