Precoated layers reversed-phase chromatography

Chapter 3 through Chapter 8 deal with the basic aspects of the practical uses of PLC. Chapter 3 describes sorbent materials and precoated layers for normal or straight phase (adsorption) chromatography (silica gel and aluminum oxide 60) and partition chromatography (silica gel, aluminum oxide 150, and cellulose), and precoated layers for reversed-phase chromatography (RP-18 or C-18). Properties of the bulk sorbents and precoated layers, a survey of commercial products, and examples of substance classes that can be separated are given. 

Precoated plates are also available for reversed-phase liquid-liquid partition thin-layer chromatography. Here the silica gel has been treated with an octadecyl silylating reagent thus coating the particles with a non-polar chemically-bonded thin film. The solvent employed is more polar than the film and chromatographic development results from partition between these two phases. 

Amino-modified precoated silica layers In the case of the NH2-modified precoated layers, the amino group is bonded via a propyl group as a spacer onto the silica gel. Besides their use in a straight-and a reversed-phase retention mechanism, a further possibility is application in ion-exchange chromatography. This special use is described in Section III.A.3. Typical applications with amino-modified precoated layers used in straight- or reversed-phase mechanisms are, among others, separations of barbiturates and steroids (142, 143), carbohydrates (144-146), phenols and xanthin derivatives (147). and purines and pyrimidines (148,149). 

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