Column chromatography chromatographic results from

So far the plate theory has been used to examine first-order effects in chromatography. However, it can also be used in a number of other interesting ways to investigate second-order effects in both the chromatographic system itself and in ancillary apparatus such as the detector. The plate theory will now be used to examine the temperature effects that result from solute distribution between two phases. This theoretical treatment not only provides information on the thermal effects that occur in a column per se, but also gives further examples of the use of the plate theory to examine dynamic distribution systems and the different ways that it can be employed. 

The resulting product is purified by column chromatography on 90 g of silica gel eluting with a mixture of 30% ethyl acetate in petroleum ether (Note 13). The chromatographed material is further purified by recrystallization from diethyl ether/pentane (2 1) to give 7.1 g (78%) of 2-(4-methoxyphenyl)-2-cyclohexen-1-one as a pale yellow solid, mp 58-59°C (Note 14). An additional 1.6 g (18% mp 58-59°C) can be isolated by concentration of the mother liquor and column chromatography of the residue on 30 g of silica gel eluting with a mixture of 10% ethyl acetate in petroleum ether. 

In principle, h.p.Lc. arose from conventional liquid column chromatography, following the development of g.l.c. and realisation that it was a rapid and accurate analytical method. This led to a reappraisal of the liquid column chromatographic system, which in turn resulted in research developments in instrument design and in the manufacture of column-packing materials. These now have precise specifications to make them suitable for adsorption, normal and reversed phase partition, ion exchange, gel permeation, and more recently affinity chromatography. 

Use is made of this relationship in chromatography in calculating the total zone spreading that results from multiple sources. To get the total zone width a, the variances of the individual sources of zone spreading are summed and the square root is taken. For example, if a chromatograph has appreciable volumes in the tubing used to connect the column to the detector and to the injection valve, these will add to the total width of the peak. The total peak width aT is... 

Liquid-Liquid Chromatography. Liquid-liquid chromatographic (LLC) separations result from partitioning of solute (analyte) molecules between two immiscible liquid phases (10). The liquid mobile and liquid stationary phases ideally have little or no mutual solubility. The stationary liquid phase is dispersed on a column of finely divided support. The use of a nonpolar mobile phase and a polar stationary phase is referred to as normal phase LLC. Under these conditions, less polar solutes are preferentially eluted from the column. Reverse phase chromatography employs a nonpolar stationary phase and a polar mobile phase. Generally, polar compounds elute more rapidly with this technique. Reverse phase chromatography, useful for the separation of less polar solutes, has found increased application in occupational health chemistry. It is optimally suited to the separation of low-to-medium molecular weight compounds of intermediate polarity. 

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