PUB - Publikationen an der Universität Bielefeld

The inner wall surface topography of fused silica capillaries with an inner diameter of 50 µm, coated with linear polyacrylamide layers of different quality, was investigated by atomic force microscopy (AFM). After electropherograms were recorded of a synthetic mixture of proteins in a capillary having a given coating, the capillary was fragmented into many small pieces, and some of the fragments whose inner surface was easy to access by the cantilever were randomly selected and probed by AFM. A correlation between coating quality and capillary electrophoresis (CE) performance was observed. A comparison between both CE and AFM data from the same capillary indicates that those capillaries having zones with nonhomogeneous coatings, i.e., those having higher surface roughness, give poorer CE separation performances than those with a homogeneous polyacrylamide coating. The polymeric coating of these later capillaries showed typical thickness values of a few nanometers. The reduced CE performance observed in those capillaries with higher roughness is probably associated with the noxious adsorption of proteins directly onto the bare or thinly coated inner wall of the fused silica capillaries.