Preparative layer chromatography principles

Further purification of HP-j8-CDs can be carried out through the thin layer chromatography. A formula for developing was propanol, ethyl acetate, aqua ammonia and water were prepared by 6 1 1 3, or acetonitrile, water, aqua ammonia was mixed by 6 3 1, the latter formula has a shorter developing time. The color development reagents are cerous sulfate 1 g, ammonium molybdate 24 g, concentrated sulfuric acid 50 mb, 450 mL deionized water. Because of the adsorption principle of the silica gel, the more the substituent on the HP- -CDs, the faster the molecules will move. Therefore, the high DS HP-)3-CDs move a long distance. Furthermore, HP-j8-CDs can be purified by sihca column. The mobile phase was chloroform/methanol (100 1) [26]. 

Thin layer chromatography may be either carried out by the adsorption principle (if the thin layer is prepared by an adsorbent such as Kieselguhr, or alumina) or by the partition principle (if the layer is prepared by a substance such is silica gel which holds water like the paper). More recently, thin layer gel filtration chromatography Is also performed as we will see later. In this case, the layer is made up of controlled pore beads of various gels. 

Principles and Characteristics Supercritical fluid extraction uses the principles of traditional LSE. Recently SFE has become a much studied means of analytical sample preparation, particularly for the removal of analytes of interest from solid matrices prior to chromatography. SFE has also been evaluated for its potential for extraction of in-polymer additives. In SFE three interrelated factors, solubility, diffusion and matrix, influence recovery. For successful extraction, the solute must be sufficiently soluble in the SCF. The timescale for diffusion/transport depends on the shape and dimensions of the matrix particles. Mass transfer from the polymer surface to the SCF extractant is very fast because of the high diffusivity in SCFs and the layer of stagnant SCF around the solid particles is very thin. Therefore, the rate-limiting step in SFE is either... 

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