title: Protein separation and surfactant control of electroosmotic flow in poly(dimethylsiloxane)-coated capillaries and microchips.
abstract: A thermally pyrolyzed poly(dimethylsiloxane) (PDMS) coating intended to prevent surface adsorption during capillary electrophoretic (CE) [Science 222 (1983) 266] separation of proteins, and to provide a substrate for surfactant adsorption for electroosmotic mobility control was prepared and evaluated. Coating fused-silica capillaries or glass microchip CE devices with a 1% solution of 100 cSt silicone oil in CH2Cl2, followed by forced N2 drying and thermal curing at 400 degrees C for 30 min produced a cross-linked PDMS layer. Addition of 0.01 to 0.02% Brij 35 to a 0.020 M phosphate buffer gave separations of lysozyme, cytochrome c, RNase, and fluorescein-labeled goat anti-human IgG Fab fragment. Respective plates/m typically obtained at 20 kV (740 V cm(-1)) were 2, 1.5, 1.25, and 9.4-10(5). In 50 mM ionic strength phosphate, 0.01% Brij 35 running buffer, the electroosmotic flow observed was about 25% of that in a bare capillary, and showed no pH dependence between pH 6.3-8.2. Addition of sodium dodecylsulfate (SDS) or cetyltrimethylammonium bromide (CTAB) to this running buffer allowed ready control of electroosmotic mobility, mu(eo). Concentrations of SDS between 0.005 to 0.1% resulted in mu(eo) ranging from 3 to 5 x 10(-4) cm2 V(-1) s(-1). Addition of 1 to 2.3 x 10(-4)% (2.7-6.3 microM) CTAB caused flow reversal. CTAB concentrations between 3.5 x 10(-4) and 0.05% (0.0014-1.37 mM) allowed control of mu(eo) between -1 x 10(-4) and -5.0 x 10(-4) cm2 V(-1) s(-1). For both surfactants the added presence of 0.01% Brij 35 provided slowly varying changes in mu(eo) with charged surfactant concentration.
authors.affiliation: Department of Chemistry, University of Alberta, Edmonton, Canada.
authors.forename: M Youssouf
authors.initials: MY
authors.lastname: Badal
authors.forename: Margaret
authors.initials: M
authors.lastname: Wong
authors.forename: Nghia
authors.initials: N
authors.lastname: Chiem
authors.forename: Hossein
authors.initials: H
authors.lastname: Salimi-Moosavi
authors.forename: D Jed
authors.initials: DJ
authors.lastname: Harrison
mesh_terms: D002412:Cations; D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D019075:Electrophoresis, Capillary / Q000379:methods*; D008904:Miniaturization; D009995:Osmosis; D011506:Proteins / Q000302:isolation & purification*; D012828:Silicones / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D002412:Cations; D004129:Dimethylpolysiloxanes; D011506:Proteins; D012828:Silicones; D013501:Surface-Active Agents; C013830:baysilon