Monoliths are considered to be the latest version of stationary phases for
protein chromatography. They are now becoming popular since they exhibit re
duced peak broadening due to low mass transfer resistances. A weak point of
monoliths may be an inhomogeneous bed, especially when charged groups are
present during co-polymerization. This becomes apparent when a protein solu
tion is loaded onto such a monolith. A biphasic breakthrough curve differin
g from the sigmoidal-shaped one, is observed. Two error functions were used
to approximate the breakthrough curve. From these parameters an estimate o
f the fraction of flow passing through the homogeneously packed part of the
bed as well as the inhomogeneously one was derived. This flow pattern was
also confirmed by perfusing ferritin through an inhomogeneous monolith and
comparing it to an intact one. Electron microscopy and mercury porosimetry
did not indicate any abnormalities in the bed. (C) 2001 Elsevier Science B.
V. All rights reserved.