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Thin-layer chromatography (TLC) is a chromatography technique that separates components in non-volatile mixtures. [1] It is performed on a TLC plate made up of a non-reactive solid coated with a thin layer of adsorbent material. [2] This is called the stationary phase. [2]
Colloidal silica gel with light opalescence. Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other liquids, or may be filled by gas or vacuum.
In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the mobile phase, which carries it through a system (a column, a capillary tube, a plate, or a sheet) on which a material called the stationary phase is fixed ...
The chiral stationary phase can be prepared by mixing chirally pure reagents such as L-amino acid, or brucine, or a chiral ligand exchange reagent with silica gel slurry, [2] [3] or by impregnation of the TLC plate in the solution of a chiral reagent. [4]
For example, one class of the most commonly used chiral stationary phases both in liquid chromatography and supercritical fluid chromatography is based on oligosaccharides [4] such as Amylose Cellulose or Cyclodextrin (in particular with β-cyclodextrin, a seven sugar ring molecule) immobilized on silica gel.
Charge carrier density, also known as carrier concentration, denotes the number of charge carriers per volume. In SI units, it is measured in m −3. As with any density, in principle it can depend on position. However, usually carrier concentration is given as a single number, and represents the average carrier density over the whole material.
The particle size of the stationary phase is generally finer in flash column chromatography than in gravity column chromatography. For example, one of the most widely used silica gel grades in the former technique is mesh 230 – 400 (40 – 63 μm), while the latter technique typically requires mesh 70 – 230 (63 – 200 μm) silica gel. [6]
The spot capacity (analogous to peak capacity in HPLC) can be increased by developing the plate with two different solvents, using two-dimensional chromatography. [8] The procedure begins with development of a sample loaded plate with first solvent. After removing it, the plate is rotated 90° and developed with a second solvent.