Electroosmotic flow suppression in capillary electrophoresis: Chemisorption of trimethoxy silane-modified polydimethylacrylamide

Abstract

Adsorbed polymers are widely used to suppress electroosmotic flow (EOF) in capillary electrophoresis (CE). Polymeric coatings, physisorbed onto the surface of the capillary wall, are often unstable under harsh conditions. This can be attributed to the reversible nature of the coating which becomes apparent when the adsorbed layer competes with a second species in the electrophoresis buffer solution for attachment/interaction with the capillary surface. In an effort to overcome the problem of coating instability, trimethoxysilane-modified polydimethylacrylamide was synthesized. This copolymer rapidly adsorbs on the wall from ultradilute aqueous solutions. After incubation at a temperature of 60 degrees C silyl groups, which extend from the polymer backbone, form condensation bonds with the silanols on the capillary surface. This enables subsequent formation of strong covalent bonds between the copolymer and the capillary wall. In this research, we establish that physisorption of polymer chains to the surface is essential for close alignment of surface and polymer silane groups which facilitates the formation of covalent bonds.

Femtosecond laser microstructuring: an enabling tool for optofluidic lab‐on‐chips

“…Prior to this experiment, the inner walls of the microchannel network were coated with a polymer [88] in order to suppress the EOF and to minimize adsorption of DNA molecules on the channel wall. Subsequently, the channels were filled with a sieving gel matrix [89] in order to maximize the resolution of MCE separation.…”

CE as orthogonal technique to HPLC for alprazolam degradation product identification

“…Furthermore, this second effect will permit us to switch the direction of the EOF which in practice is almost essential in order to have short analysis times. Similar polymeric coatings have been successfully applied for EOF control [37][38][39][40] but tedious coating procedures are needed in most cases [41]. Our approach just takes 15 min to prepare the coating and it does not need any special instrumentation.…”

Combined microfluidic-optical DNA analysis with single-base-pair sizing capability

“…Employing tunable, astigmatic beam shaping [36], an elliptical cross section of the written waveguide was obtained, with a major diameter of ~50 µm in the vertical direction, while the minor diameter in the horizontal direction is ~12 µm in order to retain a high spatial resolution along the direction of DNA migration and separation. Prior to the experimental runs the inner walls of the microfluidic channel network were coated with an epoxy-poly-(dimethylacrylamide) (EPDMA)-based polymer [37]. Subsequently, the channels were filled with a sieving gel matrix consisting of hydroxyethylcellulose (HEC) (2% wt./vol.)…”