Paper chromatography. Thin-layer

Because polyphenolics show chemical complexities and similar structures, isolation and quantification of the individual polyphenolic compounds have been challenging. Many traditional techniques (paper chromatography, thin-layer chromatography, column chromatography) have been used. HPLC, with its merits of exacting resolution, ease of use, and short analysis time, has the further advantage that separation and quantification occur simultaneously. A reversed-phase HPLC apparatus equipped with a diode array detector makes possible the easy isolation and separation of many polyphenolics. For enhanced performance of HPLC separation, the polyphenolics should first be isolated into several fractions to effectively separate the individual polyphenolics (Jaworski and Lee, 1987 Oszmianski and Lee, 1990). 

Whichever technique is used - paper chromatography, thin layer chromatography, a column of material - separation will be achieved, but different rates of flow or i f value will be recorded. Different powders are used to achieve different separations. Research in the area of analytical chemistry means that different variations of the techniques are being developed periodically. The products can be separated using chromatography then the separated components characterized using mass spectrometry or various types of spectroscopy. 

As a rule, chemical methods used in the examination of writing materials require initial preparation of a sample for study. Paper chromatography, thin-layer chromatography and capillary electrophoresis are experimental techniques often applied. These methods lead primarily to separation of the dyes contained in the ink under examination and to the discrimination of ink samples. The techniques are simple to use, require a small amount of sample for examination, are selective and give reproducible results. Their basic disadvantage, however, is the necessity to isolate the ink from the substrate (e.g. paper) on which the examined document has been prepared. Solvent extraction of the ink often leads to partial damage of the document. 

See liquid chromatography gas chromatography paper chromatography thin-layer chromatography ion-exchange chromatography gel filtration. 

Thin layer chromatography is very similar to paper chromatography. Thin layer chromatography has a wide variety of possibilities depending on the choice of the stationary phase. Adsorption, distribution and ion chromatography can be carried out in thin layer chromatography. 

Like paper chromatography, thin-layer chromatography is a form of plane chromatography in that the stationary phase is held on a plane rather than in a column. Table 12.1 lists important stationary phases used in TLC along with the respective predominant sorption process operative with each of them. The solid phase is supported on to glass, metal or a plastic substance. (Microscope slides... 

Hoye, A (1967) Determination of radiochemical pinity of some radiochemicals and pharmaceuticals by paper chromatography, thin-layer chromatography and high voltage electrophoresis. J... 

Color reactions Separation schemes Spectrofluorometry Electrophoresis Paper chromatography Thin-layer chromatography... 

Rf value A measure of the relative distance traveled by a sample in a chromatography experiment. It is obtained by dividing the distance traveled by the solvent front into the distance traveled by the sample. Under standard conditions, the Rp value is characteristic of a particular substance. See paper chromatography thin-layer chromatography. 

Other types include column chromatography, paper chromatography, thin layer chromatography (TLC), high-performance liquid chromatography (HPLC), gas chromatography (GC), supercritical fluid chromatography (SFC)... 

Planar chromatography works in similar fashion, except that the stationary phase is a flat sheet of absorbent material such as paper. Components of the mixture are held back by the stationary phase either by adsorption (e.g. on the surface of alumina) or because they dissolve in it (e.g. in the moisture within paper). See paper chromatography thin-layer chromatography. 

Paper chromatography Thin layer chromatography High performance liquid chromatography Paper electrophoresis... 

Compared to paper chromatography, thin layer is more versatile, faster and more reproducible. It is often used as pilot technique to quickly determine the complexity of a mixture. It may otherwise be used as an aid in order to find out the best conditions for large-scale chromatography. Because of its speed and simplicity, it is often used to follow the course of reactions. Thin layer technique has often been used to identify drugs, contaminants and adulterants. It has also been widely used to resolve plant extracts and many other biochemical preparations. 

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