Two-dimensional thin-layer chromatography 2D TLC

Two-dimensional thin-layer chromatography (2D-TLC), is particularly effective in the case of complex extracts when one-dimensional developing yields partial separation. Moreover, it offers the possibility of modifying separation procedures when the development direction is changed. 

Two-dimensional thin-layer chromatography (2D TLC) involves the application of a single sample to one corner of a TLC plate, which is subjected to two development processes. The TLC plate is developed with the first mobile phase, dried, and redeveloped in an orthogonal (the plate rotated through 90°) direction with a second mobile phase having different selectivity characteristics. Thus, the components migrate from the point of application into a two-dimensional thin layer, ensuring more space for resolution compared to one-dimensional separation. 

FIGURE 3.24 Two dimensional thin layer chromatography (2D-TLC). (a) A sample is spotted at one comer of the plate (h) the plate is developed in one direction (c) the plate is rotated 90° (d) the plate is developed in the second direction with a different solvent. 

Since 5/J, S-epimers of 5/f,8/f-lyseigic acid derivatives are artefacts their occurrence is not mentioned beside the natural alkaloid, e.g., only eigometrine, not ergometrinine Identification of all ergoUnes by isolation and comparison with authentic samples by means of two dimensional thin-layer chromatography (2D-TLC)... 

This effect is illustrated in Fig. 17.1. Multidimensional chromatography separations can be done in planar systems or coupled-column systems. Examples of planar systems include two-dimensional thin-layer chromatography (TLC) (Consden et al., 1944 Grinberg et al., 1990), where successive one-dimensional TLC experiments are performed at 90° angles with different solvents, and 2D electrophoresis, where gel electrophoresis is run in the first dimension followed by isoelectric focusing in the second dimension (O Farrell, 1975 Anderson et al., 1981 Celis and... 

Two-dimensional displacement thin-layer chromatography (2D-D-TLC) of ecdysteroids was also introduced. Samples of natural origin (plant extracts) were investigated by 2D-D-TLC. The first dimensional run separated the ecdysteroids from the majority of the contaminating compounds (e.g., flavonoids) while the second dimensional run improved the separation, and concentrated the spots into sharp bands. 

FISH, fluorescence in situ hybridization HPLC, high-performance liquid chromatography MS, mass spectrometry NMR, nuclear magnetic resonance PCR, polymerase chain reaction RT, reverse transcription TLC, thin-layer chromatography 2D-PAGE, two-dimensional polyacrylamide gel electrophoresis. 

Two-dimensional analytical techniqnes can combine two similar (e.g., 2D thin-layer chromatography [TLC] [cf. Section 11.3] or 2D gel electrophoresis [cf. Section 11.3]) separation procedures by sequentially varying the mobile phase compositions and developing with the second phase in a direction perpendicnlar to the hrst. 

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