Thin-layer chromatography occupies a leading position in the quantitative and semi-quantitative analysis of complex pharmaceutical, natural, biomedical, technological, chemical and many other substances. Thin layer chromatography is also the most affordable mass analysis method for virtually any class of substance.
This technique of separation and analysis of multicomponent systems is widely used in laboratories of various specificities and directions: sanitary-epidemiological, veterinary, agrochemical, research, criminalistic, as well as at plant protection stations, standardization centers and forensic medical examination bureaus .
The main advantages of thin-layer chromatography, based on the movement of the eluent (analyte solvent) in the sorbent layer due to the so-called capillary forces, are the simplicity and ease of the chromatographic process, a high degree of analysis accuracy and the relatively low cost of the necessary equipment.
Thin-layer chromatography, having a high degree of sensitivity (low detection threshold) and selectivity, allows you to determine 10-20 ΞΌg of substances with an accuracy of 7%, which is a very high indicator. Thin layer chromatography can be of the adsorption and distribution types. The most widely used is the first option.
The essence of the method of thin-layer chromatography is the movement of the solvent of the substance in the sorbent layer and the spatial distribution of different components depending on their individual characteristics and properties. The fact is that molecules of different composition and structure are sorbed (deposited) on the solid surface of the chromatographic plate in different ways. Therefore, complex multicomponent systems are gradually divided into separate components.
Moving at different speeds along the sorbent layer, individual, already separated, components form a chromatogram. Each color spot corresponds to a specific chemical. Colorless substances are illuminated with ultraviolet light, under the influence of which many compounds begin to fluoresce, or are treated with a special coloring reagent.
Among modern analytical methods , gas-liquid chromatography is especially notable. This method of separation and analysis is characterized by the use of a special non-volatile liquid as a sorbing substance, which is wetted by a powdery ceramic material. And as a driving medium, various inert gases are used here . This method is the most effective for the study of complex mixtures, which contain hundreds of different components.
Another modern method for studying the composition of complex substances is liquid chromatography. The principal feature of this method is the separation of individual components by using differences in their distribution between the mobile (eluent) and the stationary (sorbent) phases. This method is most often used in the analysis of various organic compounds (food additives, pesticides, various toxins, etc.). Also, this method of chromatographic research is used to control the quality of pharmacological preparations, determine the content of steroids in biological fluids, amino acid analysis and other things.