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Handbook of Thin-Layer Chromatography Third Edition,Revised and Expanded edited by Joseph Sherma & Bernard Fried

TLC stands for thin-layer chromatography, which is a chromatography technique for separating non-volatile substances. Thin-layer chromatography uses an inert substrate like glass, plastic, or aluminium foil that is coated with a thin layer of adsorbent material, commonly silica gel, aluminium oxide (alumina), or cellulose. The stationary phase refers to the adsorbent layer.

A solvent or solvent mixture (known as the mobile phase) is drawn up the plate via capillary action after the sample has been put to the plate. Separation is achieved because different analytes ascend the TLC plate at different rates. The stationary phase and the mobile phase have different properties. Non-polar mobile phases, such as heptane, are utilised with silica gel, which is a relatively polar material. Chemists can fine-tune the bulk characteristics of the mobile phase by using a mixture as the mobile phase.

The spots are displayed after the experiment. The sheets are often coated with a phosphor, and black spots form on the sheet where chemicals absorb the light impinging on a particular location. Spots can also be visualised by chemical processes; anisaldehyde, for example, creates colourful adducts with a variety of compounds, and sulfuric acid chars most organic molecules, leaving a black spot on the sheet.

To quantify the results, the retardation factor, also known as the retention factor, is calculated by dividing the distance travelled by the material under consideration by the total distance travelled by the mobile phase. The solvent absorption must be halted before the mobile phase reaches the end of the stationary phase for the result to be quantitative. In general, a material with a structure similar to the stationary phase would have a low Rf, whereas one with a structure similar to the mobile phase will have a high Rf. The characteristics of retardation factors vary based on the particular situation of the mobile and stationary phases. As a result, scientists frequently apply a sample of a known compound alongside the unknown compounds to the sheet.

Thin-layer chromatography can be used to track a reaction's progress, identify components in a given mixture, and determine a substance's purity. Assessing ceramides and fatty acids, detecting pesticides or insecticides in food and water, analysing the dye content of fibres in forensics, assaying the radiochemical purity of radiopharmaceuticals, or identifying medicinal plants and their constituents are all examples of these applications.

The original method can be improved in a variety of ways, including automating the various procedures, increasing the resolution gained using TLC, and allowing for more precise quantitative analysis. HPTLC, or "high-performance TLC," is the name given to this approach. HPTLC typically employs thinner stationary phase layers and smaller sample volumes, reducing resolution loss due to diffusion.

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