SEPARATION OF VERY HYDROPHOBIC COMPOUNDS BY HYDROPHOBIC INTERACTION ELECTROKINETIC CHROMATOGRAPHY

Separations of very hydrophobic neutral analytes were achieved using h ydrophobic interaction electrokinetic chromatography (HI-EKC). Alkyl a ryl ketone homologues dodecanophenone (C-18), tetradecanophenone (C-20 ), hexadecanophenone (C-22) and octadecanophenone (C-24) were separate d via hydrophobic interactions between free sodium dodecyl sulfate (SD S) monomers and the analytes. The first running buffer consisted of 50 mM SDS and 50% acetonitrile (pH 7.0). A complete reversal in the elut ion order of these analytes was obtained with the second running buffe r, 20 mM cetyltrimethylammonium bromide (CTAB) and 50% acetonitrile (p H 2.8). With the second running buffer, electroosmotic flow was suppre ssed and the free CTAB monomers migrated toward the detector. Through hydrophobic interactions between the free CTAB monomers and the analyt es, separations of these very hydrophobic alkyl aryl ketones were obta ined in less than 10 min; analysis times were less than 5 min with the SDS-based separations.