Capcell Pak C18 AQ series HPLC columns are designed and developed by varying the type and amount of silicone polymer and functional groups so as to retain highly polar compounds and enable the use of 100% water as the mobile phase. The peak shape of basic compounds is symmetrical without tailing even under acidic conditions that are typical of LC/MS analyses. The columns are available in capillary, cartridge, semi-microcolumn, and standard dimensions and in 5 μ and 3 μ particle sizes.