Chromatography, column paper

Column, paper, liquid and thin-layer chromatography.Ill... 

Column, paper, liquid, thin-layer and ion exchange chromatography. 119... 

Because of the instability of many of the compounds involved, it is necessary to determine the chemical recoveries in all cases. This requires the use of macro quantities (10 mg up to several hundred mg) of carriers and target compounds. This, in turn, makes it impractical to use the various thin-layer methods, such as paper and thin-layer chromatography and paper electrophoresis, although such methods have proved useful in identifying products and in checking the purity of fractions. The separation methods now most commonly used are column chromatography and sublimation. 

Peschanski, using the isotopic method ( ° Hg), has found complete exchange (0 °C) in methanol and various other non-aqueous media. The separation methods used were, (a) paper and column chromatography, (b) paper electrophoresis, and (c) precipitation of Hg(I) with chloride. In the presence of cyanide ions, however, less than complete exchange could be observed. Zero-time exchange was again found to vary in the same manner as for aqueous media. Similar effects were observed in the presence of chloride ions. 

The problem of determining V-j in SEC is similar to that of determining zero retention time (tg) in other liquid chromatography columns. Recently, there have been several papers dealing with the determination of retention time of a retained peak in HPLC (12-19). In high-performance reversed-phase chromatography, McCormick and Karger (1 ) and Berendsen, et al., (16) have employed D2O to measure tg. Neidhart et al.,... 

Before discussing the various derivatives that have been used, it should be remembered that oligosaccharides are often obtained by chromatography on paper or on cellulose columns, and this may cause them to become contaminated by xylan this may be eliminated by extraction of the crude fractions with hot ethanol.474 For similar reasons, glucose that is really extraneous may be detected in fractions separated by electrophoresis on cellulose acetate.475 Gas-liquid chromatography was used to show the presence in pituitary glyco-... 

There are many other forms of chromatography besides paper chromatography. In column chromatography, the mixture to be separated is loaded at the top of a column of sandlike material. A solvent passing through the column pulls the components of the mixture through the material at different rates. As the purified components drip out the bottom of the column at different times, they can be collected in separate flasks. 

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). 

Product separation Paper chromatography of products Thin layer chromatography Column chromatography (419) (420) (380)... 

With regard to terminology, we will use FI to mean flow injection as described above with an injection valve for sample introduction. Similarly, we will use SI as described above to mean sequential injection in which solutions are pulled into a holding coil via a multiposition valve, and pushed out through this valve to the separation system. The combination of a SI fluid-handling system with a separation column can be called SI chromatography. Some papers apply FI and SI terms more loosely to flow-based systems that may or may not follow these formal fluid-handling approaches as just defined. 

A new method for the rapid separation of alkaloids, inter alia atropine, has been elaborated, using chromatography on paper that is impregnated with zirconium oxide.57 Cation-exchange h.p.l.c. analysis of tropane alkaloids has been developed,58 followed by post-column derivatization using the fluorimetric ion-pair technique.58,59 Gas chromatography of tropanes has been reviewed.60... 

There are two popular LC techniques in which the stationary bed is supported on a planar surface rather than in a column paper chromatography (PC) and thin-layer chromatography (TLC). PC preceded TLC by some 10 to 15 years, and a large number of excellent separations were devised for it. But beginning about 1956, it was found that TLC could also be used for most of these separations and that it was faster, more reproducible, more versatile, and more convenient. As a result, most laboratories have abandoned the use of PC with its large cumbersome glass chambers. Those who have not, continue to use PC because they feel that the original PC methods are superior or because of the lower cost of PC. 

Extensive use of column chromatography has been necessary to separate the Rauwolfia alkaloids, and in this connection attention is drawn to a publication which concerned itself with the more refined technique of gradient elution chromatography (123). Paper chromatography has been used extensively for analytical, fractionation, and identification purposes (124, 15). This tool is not particularly useful for the assay of crude extracts, since certain alkaloids show up clearly whereas others cannot be resolved. More information as to specific alkaloidal composition is better obtained from more highly purified fractions. 

Since the fractionation of methylated sugars by paper chromatography, column chromatography, and paper electrophoresis, as well as the properties of the methyl ethers of common sugars and their most suitable derivatives, have been described in previous Volumes of this Series and elsewhere, only a few special points and some recent advances will be discussed here. 

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