Page 249 - Multidimensional Chromatography

Foods, Flavours and Fragrances Applications 243

Often, planar chromatography is used as a preparative step for the isolation of sin-
gle components or classes of components for further chromatographic separation or
spectroscopic elucidation. Many planar chromatographic methods have been devel-
oped for the analysis of food products, bioactive compounds from plant materials,
and essential oils.
The separation capacity of a TLC method can be easily improved by use of a two-
dimensional high performance TLC technique (2D HPTLC). Various plant essential
oils (menthae, thymi, anisi, lavandulae, etc.) have been analysed by 2D TLC with
florisil (magnesium silicate) as the adsorbent, using dichloromethane/n-heptane (4 : 6)
in the first direction and ethyl acetate/n-heptane (1 : 9) in the second direction (69).

Figure 10.15 (a) One-dimensional OPLC development of the sixteen closely related
coumarins: optimised mobile phase, S t , 1.55, P s , 271 (7% ethyl acetate, 52.9% chloroform,
20% dichloromethane and 20.1% n-hexane); development time, 30 min. (b) Two-dimensional
OPLC development of the same coumarins system: mobile phase, 100% chloroform in direc-
tion (a) for 55 min, and 30% ethyl acetate in direction (b) for 80 min. Compound identification
is as follows: (1) umbelliferone; (2) herniarin; (3) psoralen; (4) osthol; (5) apterin; (6)
angelicin; (7) bergapten; (8) oxypeucedanin; (9) isobergapten; (10) scopoletin; (11) sphondin;
(12) xanthotoxin; (13) imperatorin; (14) pimpinellin; (15) isopimpinellin; (16) new
archangelicin derivate. Reprinted from Journal of Planar Chromatography, 3,P. Härmälä
et al., ‘Two-dimensional planar chromatographic separation of a complex mixture of closely
related coumarins from the genus Angelica’, pp. 515–520, 1990, with permission from Prof.
Sz. Nyiredy, Research Institute for Medicinal Plants, Budakalász, Hungary.