Agilent HPLC Column Selection Guide

Columns for Analytical HPLCZORBAX 80Å Extend-C18OSiC18• High efficiency and long life at high pH – up to pH 11.5• Unique bidentate bonding and double endcapping provides high pH stability• More efficiency and better peak shape than polymer-based columns• Improve retention, resolution and peak shape of basic compounds• High sensitivity for LC/MS separations of peptidesSiO C18Silica SupportThe Agilent ZORBAX Extend-C18 column uses a novel bidentate C18-C18 bonding technologyto make it possible to develop high-resolution separations at high pH with a silica-basedcolumn. At high pH, non-charged basic compounds will not interact with the underlying silica.The result is high efficiency separations with superior peak shape and improved resolution.High pH separations are also the best choice for compounds that are more stable or moresoluble in high pH solutions. Some of the mobile phase buffer options for high pH includetriethylamine, pyrrolidine, glycine, borate and ammonium hydroxide. Ammonium hydroxideat pH 10.5 is an excellent mobile phase modifier for the LC/MS of peptides and smallmolecules with improved sensitivity compared with TFA containing mobile phase at low pH.The Extend-C18 column is stable from pH 2-11.5 with good peak shape for all types ofcompounds. Extend-C18 columns also provide an additional selectivity choice at low pH.Novel Bidentate C18-C18 Bonding forExtend C-18 Bonded PhaseColumn SpecificationsBonded PhasePoreSizeSurfaceAreaTemp.Limits* pH Range** EndcappedCarbonLoadZORBAX Extend-C18 80Å 180 m 2 /g 60°C 2.0-11.5 Double 12.5%Specifications represent typical values only.*Temperature limits are 60°C up to pH 8, 40°C from pH 8-11.5.**Above pH 6 highest column stability for all silica based columns is obtained by reducing the operating temperature to40°C or below and using lower buffer concentrations (0.01 - 0.02M) or organic buffers.52 Order online at www.agilent.com/chem/store