title: Fabrication and chromatographic performance of porous-shell pillar-array columns.
abstract: We report on a new approach to obtain highly homogeneous silica-monolithic columns, applying a sol-gel fabrication process inside a rectangular pillar-array column (1 mm in width, 29 microm in height and 33.75 mm in length) having a cross-sectional area comparable to that of a 200 microm diameter circular capillary. Starting from a silicon-based pillar array and working under high phase-separation-tendency conditions (low poly(ethylene glycol) (PEG)-concentration), highly regular silica-based chromatographic systems with an external porosity in the order of 66-68% were obtained. The pillars, 2.4 microm in diameter, were typically clad with a 0.5 microm shell layer of silica, thus creating a 3.4 microm total outer pillar diameter and leaving a minimal through-pore size of 2.2 microm. After mesopore creation by hydrothermal treatment and column derivatization with octyldimethylchlorosilane, the monolithic column was used for chip-based liquid-chromatographic separations of coumarin dyes. Minimal plate heights ranging between 3.9 microm (nonretaining conditions) and 6 mum (for a retention factor of 6.5) were obtained, corresponding to domain-size-reduced plate heights ranging between 0.7 and 1.2. The column permeability was in the order of 1.3 x 10(13) m(2), lower than theoretically expected, but this is probably due to obstructions induced by the sol-gel process in the supply channels.
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering, Belgium.
authors.forename: Frederik
authors.initials: F
authors.lastname: Detobel
authors.forename: Selm
authors.initials: S
authors.lastname: De Bruyne
authors.forename: Joris
authors.initials: J
authors.lastname: Vangelooven
authors.forename: Wim
authors.initials: W
authors.lastname: De Malsche
authors.forename: Tim
authors.initials: T
authors.lastname: Aerts
authors.forename: Herman
authors.initials: H
authors.lastname: Terryn
authors.forename: Han
authors.initials: H
authors.lastname: Gardeniers
authors.forename: Sebastiaan
authors.initials: S
authors.lastname: Eeltink
authors.forename: Gert
authors.initials: G
authors.lastname: Desmet