REVERSED-PHASE LIQUID-CHROMATOGRAPHY OF DANSYL AMINO-ACIDS WITH MICROSPHERICAL OCTADECYL-SILICA AND OCTADECYL-ZIRCONIA BONDED STATIONARY PHASES

A series of non-porous, microspherical octadecyl-silica and octadecyl-zirconia bonded stationary phases were introduced and evaluated in the HPLC of dansyl-amino acids over a wide range of elution conditions. The microspherical silica and zirconia particles were coated with either polymeric or monomeric octadecylsilyl layers. Polymeric octadecyl-silica columns afforded virtually no solute-support interaction, whereas polymeric octadecyl-zirconia bonded stationary phases exhibited metallic interaction with some dansyl amino acids, and their residual adsorptivities toward the separated analytes were comparable to those observed on monomeric octadecyl-silica columns without end-capping. These metallic interactions, which are of the electron donor-electron acceptor (EDA) type, predominate in the acidic pH region. However, the presence of small amounts of tartrate or phosphate ions in the eluent greatly reduced EDA interaction, and consequently allowed the high resolution separation of dansyl amino acids (Dns-AA). Under optimal gradient elution conditions, eleven or fourteen different Dns-AA could be separated in less than 6.0 min on short polymeric octadecyl-zirconia or octadecyl-silica columns, respectively.