Page 182 - Multidimensional Chromatography

Multidimensional Planar Chromatography 175

y

x
2
Figure 8.4 Schematic diagram of the peak capacity (n ) of a 2-D planar chromatographic
system (i) the number of squares represents the number of compounds which can theoretically
be separated.

8.4 METHODS FOR THE SELECTION OF
APPROPRIATE MOBILE PHASES

Nurok and his research group (11) proposed the use of a binary mixture of a strong
and a weak solvent, because R f can be predicted as a function of the solvent compo-
sition by the use of the following equation:

log k alog X s b (8.2)

where a and b are empirical constants, X s is the mole fraction of the strong solvent
and k is the capacity factor, which is related to R f by the relationship:
1
R f (8.3)
1 k