PRP-C18 Analytical Guard Column Replacement Cartridges (5/pk), PEEKHigh efficiency separations at any pH PRP C18 columns have genuine pH and chemical stability. The stationary phase stands up to prolonged exposure to concentrations as high as 1 M NaOH and 1 M H2SO4, with no measurable decrease in performance. The support does not strip, bleed, or dissolve at any pH. It can therefore perform reliably and reproducibly throughout the extended life of the column, regardless of mobile phase conditions. Unlike a silica C18