Thin-Layer Chromatography (TLC) Techniques |
TLC Enhancements to HPTLC and PLC
Besides the manual method of classical Thin-Layer Chromatography, the technique can be enhanced to high-performance thin-layer chromatography (HPTLC) for faster and more accurate separations. Alternatively, TLC can be easily up-scaled to preparative-layer chromatography (PLC). Furthermore, depending on the optical properties of the analytes, they can be identified and quantified using visible, infrared or UV light.
TLC Techniques - Coupling TLC
Thin-layer chromatography can also be coupled on-line with spectroscopic methods as well as with other analytical and preparative separation techniques. This significantly increases separation performance for complex mixtures and the reliability of identification of individual substances.
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Apparatus of TLC Techniques
Planar chromatography is performed on TLC, HPTLC or PLC layers. These can either be prepared from loose, powdered sorbent materials, or purchased as pre-coated layers on glass, aluminum or plastic foil bases. In most cases, the superior quality and reproducibility of ready-coated layers make these preferable, particularly for in-situ, quantitative determinations or complicated separations. Pre-coated HPTLC layers are the optimal choice as they are capable of the highest separation performance and possess a very homogenous surface.
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TLC Techniques vs. Column Chromatography
The TLC, HPTLC and PLC techniques of planar chromatography possess the following advantages over column chromatography:
- Substances that remain “sitting” at the start are immediately recognizable. Also, catalytic decomposition processes can be readily detected via two-dimensional TLC
- Since chromatographic development and detection are typically separated in space and time (detection is usually performed after the mobile phase has been removed by evaporation), the use of UV-absorbing mobile phase systems poses no problems
- Substances can be detected and identified not only by using universal staining reagents, but also a wide range of selective staining reagents for specific applications
- Up to 72 samples and reference standards can be run alongside each other, and quantitatively evaluated on a single HPTLC plate
- Since chromatographic development and qualitative or quantitative evaluation do not take place on-line, the apparatus for evaluation is only required during the actual measurement process and not for the duration of the separation process
- TLC, HPTLC and PLC plates are economically priced disposables that are only used once. Hence, cleanup of the samples is often unnecessary or minimal
- Two-dimensional or multi-dimensional planar chromatography can be performed simply and economically, for example, by using two different mobile phases in two different directions, or by multiple development using different mobile phases in the same direction