Page 187 - Multidimensional Chromatography

180 Multidimensional Chromatography

Figure 8.8 Comparison of the effects of UMD and IMD on separation.

After detection of the separated non-polar components, the semi-polar com-
pounds can be separated in the next chromatographic step by the use of an optimized
solvent system of medium polarity. With this mobile phase of medium strength, the
non-polar components separated in the previous step migrate close to the solvent
front, whereas the polar components remain at the origin. The separation of the most
polar compounds is executed–after detection of the compounds separated by the
preceding chromatographic step–in the next development step with the mobile
phase of highest S T . By use of GMD with a mobile phase gradient of increasing sol-
vent strength, the authors (18) separated furocoumarin isomers, flavonoid aglycones,
and flavonoid glycosides from the same sample (Figure 8.9).
Fractionation of components into polarity groups, and their optimized separation
(followed by detection) by subsequent development steps increases the separating
capacity of the chromatographic system.

Figure 8.9 GMD separation of various naturally occurring compounds of wide polarity
range from the same sample.