Bond Elut C18 OH is a nonendcapped version of the octadecyl bonded phases that enables the silanols on the silica surface to be more active. This low-load C18 phase has well-controlled silanol activity that permits the fractionation of metabolites and enhances retention of basic compounds compared to endcapped C18. The 150 Å pore size makes it a good choice for peptide extraction and higher molecular weight compounds.