BARE SILICA, DYNAMICALLY MODIFIED WITH LONG-CHAIN QUATERNARY AMMONIUM-IONS - THE TECHNIQUE OF CHOICE FOR MORE REPRODUCIBLE SELECTIVITY IN REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

Reversed-phase high-performance liquid chromatography (RP-HPLC) on chemically bonded phases has become the most popular technique in HPLC for use in pharmaceutical and biological chemistry during the last decade. However, it is unfortunate that standardization of RP-HPLC systems developed on column packing materials from different manufacturers with theoretically identical chemically bonded phases (e.g., octadecylsilyl phases) is not possible. When using bare silica from different manufacturers and generating the reversed-phase systems by dynamic modification of the silica surfaces with long-chain quaternary ammonium ions, high reproducibility of selectivity is obtained. Further, the peak symmetries obtained for amine compounds chromatographed in these systems are very good.