Thin-Layer Chromatography (TLC)

Thin-Layer Chromatography (TLC)

Thin layer chromatography (TLC) is a chromatographic technique in which the stationary phase is a thin adsorbent layer, coated onto an inert supporting plate. An eluting (or development) solvent, for which the analyte molecules have affinity, forms the mobile phase that ascends the thin layer of the stationary phase, by capillary action. The analyte molecules, after dissolution in another suitable solvent (spotting solvent) are deposited as small spots a little above the bottom of the TLC coated plate. The spotted plate is then placed in a TLC development chamber (or glass jar), containing a small quantity of the eluting solvent and with the vapor space saturated with vapors of the eluting solvent. At the interface between the coated plate and the small eluting solvent layer at the bottom, capillary action pulls up the eluting solvent onto the TLC plate. As the eluting solvent rises, it comes into contact with the spotted analyte molecules on the TLC plate. Upon contact with the moving eluting solvent, the analyte molecules are partitioned between mobile and stationary phases, depending on their relative affinities for each phase. The mobile phase continues to move up to the top of the plate, with different molecules moving at different speeds, separating out as individual spots on the plate. The progress of separation can be monitored visually in case the molecules are colored. If fluorescent plates are used, then short wave-UV light makes the spots visible. Alternatively, several chemical staining techniques can be used.

Typical adsorbent coatings are made from Silica, Aluminum Oxide, Acetylated Cellulose and Polyamide, while materials used for inert plates include Glass, Aluminum or Plastic. Standard coated TLC plates are commercially available for various applications. Due to its low cost and high sensitivity, TLC is ideal for laboratory use, in separation and analysis of small quantities of mixtures of non-volatile organic analytes. It can also quickly verify the identity and purity of many compounds and monitor the progress of a reaction.  

Common Uses of Thin-Layer Chromatography (TLC)

• Monitor the progress of organic reactions
• Separation and purification of small quantities of organic compound
• Detection of toxic organic pesticides or insecticides in water or other liquids.
• Fingerprinting of organic extracts from medicinal plants
• Forensics
• Drug evaluation
• Environmental analysis

Advantages of Thin-Layer Chromatography (TLC)

• High sensitivity
• Rapid and economical
• Small quantity of sample.

Limitations of Thin-Layer Chromatography (TLC)

• Qualitative analysis only
• Vapor space needs to be saturated with eluent vapor to prevent eluent moving to gas phase
• Used for Non-polar or slightly polar, non-volatile organics

Industrial Applications of Thin-Layer Chromatography (TLC)

• Chemical and biochemical research and development
• Environmental analysis
• Pharmaceuticals,
• Foods and beverages,
• Forensics