EP stands for "Extended pH" range. Chromenta EP packing material is made by our proprietary grafting process that evenly incorporates organic layers on the surface of ultra-high purity (99.999% SiO2) porous silica particles. This polymer-coated Chromenta EP packing material is designed to provide excellent peak shape, high efficiency, and particularly long lifetime for use in high pH. In addition, Chromenta EP columns can be used in low and intermediate pH with excellent stability. In mid-pH range, the hybrid polymer-silica layers effectively shield analytes from the surface silanol groups, thus further improve the peak shape.