Thin layer chromatography is also called "thin layer chromatography".An analytical method for chromatographic separation after evenly coating adsorbent and supporting agent on glass or plastic plate to form a thin layer.After separating different kinds of compounds in the test material, the type of each component can be determined according to the Rf value or fluorescence characteristics of the separated components.Fit according to the area of the spotThin layer scannerThe content of each component can be determined.The sample consumption is small, the analysis speed is fast, and the equipment is simple.During the separation process, there is no change in the various components of the mixture. After separation, the components that are difficult to confirm can be transferred for other tests, which can be used as a rapid screening method when dealing with a large number of samples of different types.In judicial appraisal, it is mainly used to test various macromolecular organic compounds, such as organic components extracted from ink, dye, paint, soil, grease, alkaloid, resinman-made fiber, organic explosives, organic substances, etc.[1]
Chinese name
Thin layer chromatography
Foreign name
Thin layer chromatography
Role
Separate mixture
Purpose
Analyte separation
Advantages
Simple operation and equipment
Application
petroleum, chemical industry, medicine, biochemistry
Adsorption chromatography is the most commonly used thin-layer chromatography.Common adsorbents are silica gel, alumina, etc.Like other chromatography methods, thin-layer chromatography can also perform chromatography with the mechanism of distribution, ion exchange, molecular exclusion, etc. in addition to the adsorption method, that is, the material for laying the thin layer is correspondingly replaced by the carrier, ion exchanger, gel, etc. coated with the stationary phase, and its operation is basically the same as the adsorption method.
process
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Plate making
When laying thin layer board, the base plate shall be clean and flat, and can be laid by dry method or wet method.Currently, the wet method is commonly used to make boards, that is, to mix the adsorbent and adhesive (such as calcined gypsum) in a certain proportion, add proper amount of water to mix evenly, and then slowly move the homogenate through the base plate with a coater, place it to dry, and then use it after proper baking and activation.If the adsorbent is directly and evenly spread into a thin layer without adhesive and water, it is a dry process board.At present, there are all kinds of prepared thin slabs on the market, collectively referred to as precast slabs.
open
There are many ways, and the above line method is the most commonly used.Place the thin-layer plate vertically or obliquely, and add the developing solvent to the lower part to make it move from bottom to top.The downward rule is to use filter paper to lead the solvent to the upper end of the thin layer to make it flow from top to bottom.When developing in parallel, lay the plate flat, and the solvent is sucked up to the end of the thin-layer plate where there is a sample, and then develop.When using a circular thin plate, place the sample point near the center of the circle to move the solvent from the center of the circle to the circumference, which is called circular expansion or radial expansion;Place the sample point at the circumferential position so that the solvent moves from the circumference to the center of the circle is developed centripetally, which is suitable for the separation of components with large f values.Scrape off the adsorbent near the point sample, so that the solvent can only be developed through the narrow part near the sample point, so the solvent front edge is in an arc development mode, also known as radial development, which may be better for components that are difficult to separate.
After developing once, take out the thin layer plate to volatilize the solvent, and then use the same solvent or another solvent to develop in this direction for several times.Place the sample point at one corner of the square thin plate, first unfold it in one direction, then rotate the plate 90 °, and then unfold it in another direction in two directions.Multiple unfolding and two-way unfolding can enhance the separation effect.[2]
characteristic
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Simple operation, simple equipment, no special equipment except optical densitometer, good separation effect, short time, many samples can be separated on one board at the same time.Except for low boiling point substances, various inorganic and organic compounds can be separated.
Application and development
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It is widely used in petroleum, chemical industry, medicine, biochemistry, etc.The sample dosage is usually several to several hundred micrograms, which is a practical and effective micro separation and analysis method.This method can also be used to separate and prepare a large number of samples, that is, use a larger and thicker thin layer plate to dot the sample solution into strips at the starting point, so that milligram samples can be separated.
