| Modifying the inner-wall surface of a capillary in OTCEC is an approach to improve sample separation. The inner wall of a capillary is etched and bonded with either a C18 or a cholesteryl moiety or coated with a fluorosurfactant. In the separation of antibiotics, three comparisons of resolution are made: (1) between 20 mum and 50 mum capillaries, (2) between bare etched and etched chemically modified capillaries, (3) between bare etched and etched fluorosurfactant-coated capillaries. Resolution depends on the sample and pH. The best separations are achieved by the cholesteryl capillary for ampicillin/gentamycin and by bare etched capillaries for nystatin. The fluorosurfactant-coated capillary has improved resolution for gentamycin in comparison to the bare etched capillary. Comparable data are obtained on the 20 and 50 mum capillaries. Images of the chemically modified surfaces are obtained by AFM showing "pits" for the C-18 capillary and globular-shaped objects for the cholesterol capillary. |
