SOLID-STATE NMR-STUDIES OF IONIC SURFACTANTS ADSORBED ON CYANOPROPYL-BONDED PHASES - IMPLICATIONS FOR MICELLAR LIQUID-CHROMATOGRAPHY

Solid-state C-13 NMR spectroscopy techniques, including cross polariza tion (CP), magic angle spinning (MAS), and high-power proton decouplin g, have been used to study the interactions of two ionic surfactants, sodium dodecyl sulfate(SDS) and cetyltrimethylammonium bromide (CTAB), with the cyanopropyl bonded phase. Variable contact time CP/MAS C-13 NMR data suggest that the unusual behavior of cyanopropyl bonded phase columns in SDS and CTAB micellar reversed-phase liquid chromatography can be attributed to the strong interactions between the polar head g roup of SDS or CTAB and the cyano functionality of the polar bonded ph ase, Models which depict the structure of the surfactant-modified cyan opropyl bonded phase are proposed from the NMR data, and these models are in good agreement with the selectivity exhibited by cyanopropyl bo nded phase columns toward polar and ionogenic compounds in MLC. (C) 19 96 Academic Press, Inc.