OCTYL DERIVATIZED SILICA hplc sorbents silica gels octyl C8*60 angstroms 4 HPLC SORBENTS SILICA GELS OCTYL C8*60 AN GSTROMS 40- SILICAGEL,REVERSEDPHASE,BUTYL(C4),ULTRAPURE SILICAGEL,REVERSEDPHASE,OCTADECYL(C18),ULTRAPURE SILICAGEL,REVERSEDPHASE,OCTYL(C8),ULTRAPURE SILICAGEL,REVERSEDPHASE,PHENYL,ULTRAPURE SILICAGEL,REVERSEDPHASE,SILVERNITRATE