Bio-Rad Foresight™ Chromatography Columns, Prepacked - Manual (Page 10)

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For optimal results a phase ratio in the range of
20–40 is recommended. 9 To minimize the error,
the final liquid phase concentration should be
around 50% of the initial concentration, the exact
value however depends on the precision of the
protein concentration measurement 10 . Substituting
Eq. 5 in Eq. 2 leads to the following expression:
( )
0
q C C β = −
This expression shows how the phase ratio and
the adsorbed concentration are related. β directly
affects the depletion level of the solute phase
concentration, thus it has an effect on the uncertainty
of chromatographic HT experimentation. Optimal
values lie in the range of 20–40.
2.4 Adsorption Isotherm
An isotherm plots the solute solid and liquid phase
concentrations at equilibrium for a given set of
experimental conditions (e.g., pH, salt concentration).
The state of equilibrium, when the rates of desorption
and adsorption are equal, may be reached between
one and six hours of contact time in a Foresight™
prepacked filter plate (incubation time varies
depending on target protein and buffer conditions.
A 4–6 hr incubation time is recommended for
conservative measure).
Figure 1 is a schematic representation of an
adsorption isotherm. Figure 1A shows the operating
line. This line connects the initial state (C
0
, 0, t
0
) with
the equilibrium state (c
6
, q
6
, t
6
). The slope of the
operating line is equal to -β. During the adsorption
process the adsorbed concentration increases along
the operating line.
Eq. 6