Page 190 - Multidimensional Chromatography

Multidimensional Planar Chromatography 183

Figure 8.12 The ‘universal’ elution gradient during the stages of AMD separation: (a)
change in mobile phase composition; (b) change of solvent strength; (c) change of selectivity
value.

(20–22) for either or both orthogonal developments seems to have been rarely
recognized. Figure 8.13(a) shows a sample applied to the chromatographic plate.
After ‘n’ developments, during which the total solvent strength was reduced step-
wise at constant selectivity (Figure 8.13(b)), the compounds were separated accord-
ing to differences in polarity. In the second dimension, perpendicular to the first
(Figure 8.13(c)), the chromatographic plate was redeveloped ‘m’ times such that the
selectivity was changed at constant S T to achieve maximum spot capacity.
2-D TLC combined with multiple development is therefore a promising route
which should lead to real improvements in planar chromatography in the near future.