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Saturday, May 2, 2020

Principle and applications of TLC

TLC is one of the economical, simple, and widely used chromatographic methods in qualitative and quantitative analysis, and is used for separation and analyzes the purity of organic compounds and test the purity of compounds. Thin-layer chromatography is a type of liquid chromatography in which a stationary phase (a thin plate coated with a silica gel or alumina) and a mobile phase (a mixture of solvents) are used to analyze the molecule on a flat surface, and this process works under the capillary action, ambient temperature, and atmospheric pressure.

The principle of thin-layer chromatography (TLC):
Thin-layer chromatography also relies on the separation principle, like other chromatographic methods. The separation depends on the relative affinity of the analytes against the stationary phase and mobile phase. The analytes in the solvent mixture move over the surface of the stationary phase. The movement occurs in such a way that analytes that have a high affinity towards the stationary phase move slowly while other analytes move quickly that have less affinity. Consequently, separation of the complex mixture is achieved. When the separation process is complete, the individual analytes from the sample mixture visualized as spots at particular levels on the TLC plate.
Various essential components involved in the TLC process.
TLC plates, mobile phase, TLC chamber, filter paper, and TLC pipettes, etc.
Major steps involved in TLC procedure:
Saturation: It consists of equilibration the TLC chamber with solvent vapors.
Spotting: It consists of transferring a small volume of sample to one end of the plate.
Development:  It is a method of putting the bottom of the TLC plate in a solvent of development.
Visualization: It is a technique for viewing the distance traveled by molecules along with the stationary phase.

The various applications of TLC are as follows.
To check the sample purity: The purity of the compound can be determined by comparing it with the standard. When the impurity is observed, it shows additional spots so these can be easily identified.
Used in chemistry: Thin layer chromatography is widely used in chemistry to determine the retention factor (Rf value) by the separation and identification of molecules and also used in the determination of cations and anions in inorganic chemistry.
To identification of analytes: Another major application of TLC is it can use to separate, purification, and identification of natural substances such as glycosides, essential oils, alkaloids, pure oils, steroids, volatile oil, waxes, etc.
Used in food and cosmetic industries: The thin layer chromatography technique is used to isolate and identify the sweetening agents, colors, preservatives, foodstuffs, and some cosmetic products.
To separation of biochemical metabolites: To isolate and evaluate the biochemical constituent from blood plasma, urine, and body fluids the thin layer chromatography is useful.
Used in pharmaceuticals: Many pharmaceutical manufacturers use the TLC technique to identify impurities in a chemical substance as well as pharmaceutical formulations.
Used to determine the mobile phase: It is quick, easy, requires a minimum amount of solvent to operate, hence it is used to determine a suitable solvent system for column chromatography.
To analyze the reactions: TLC can be employed to analyze the reaction or rate of reaction and also used to check whether the reaction is completed or not.
Used in forensic science: TLC is useful in forensics to identify chemicals, including adulteration, poisoning, illegal drugs, and drug abuse.

Commonly asked questions on TLC chromatography are as follows.
 
What is the basic principle of TLC?
The TLC, paper chromatography, and high-performance thin-layer chromatography (HPTLC) are works on the same basic principle that is adsorption.

What are the three major applications of thin-layer chromatography?
The pharmaceutical, clinical, and food testing applications are 3 major application of TLC.

Why is TLC better than paper chromatography?
TLC provides better separations of analytes as compared to paper chromatography because as the stationary the TLC uses silica or alumina and paper chromatography uses cellulose paper.

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