The ODP-50 4E column has a base material of polyvinyl alcohol with a C18 ligand. Its relatively large pore size (250A) makes it suitable for the analysis of amino acids, peptides, and proteins. Usable to pH 13 so it is especially recommended for basic compounds. USP L67, Pore Size: 250A, pH range: 2-13, 100% aqueous compatible. Guard column 220-91460-00 is recommended with stainless steel coupler 220-91524-97, PEEK coupler 220-91524-98 (tubing and fittings) or 220-91524-99 (1-piece double ended.)