Diol-modified precoated silica layers

AMINO-, CYANO-, AND DIOL-MODIFIED PRECOATED SILICA LAYERS... 

Amino-, Cyano-, and Diol-Modified Precoated Silica Layers... 

Diol-modified precoated silica layers, 114 Diphenyl ether herbicides, 779-781 Directory of manufacturers and suppliers of standards, sample preparation supplies, and instruments and products for 1UC,... 

An especially pronounced selectivity of the diol-modified precoated layers exists for steroids. An example of this is the separation of some anabolic agents as shown in Fig. 7. Vicinal diol groups are fixed to the silica gel matrix by a quite nonpolar spacer. Therefore, an RP mechanism on diol... 

HPTLC separation material is available in the form of precoated layers supported by glass, plastic sheets or aluminum foil. Although precoated layers of aluminum oxide, cellulose, polyamide, ion exchange materials, reversed phase silica (alkyl bonded) have been commercially available for quite some time, the vast majority of TLC separations is carried out on normal phase silica gel, particularly in quantitative TLC analysis. Recently introduced plates modified with amino, cyano and diol functional groups bonded to the silica can be used as multimodal media. Depending on the developing solvent used, they extend normal phase or reversed phase chromatographic properties. These layers may affect the predominant role of normal phase silica gel in TLC to a certain extent. They are described in Chapter 4 of this book. Also chiral layers for the separation of optical isomers are available and cause increased interest (11). 

Chapter 3 through 6 deal with the commercial and noncommercial stationary phases used for the direct and indirect enantioseparations by means of TLC and with the chiral modifiers of mobile phases, which are used exclusively in direct separations. Chapter 3 describes the commercial chiral and nonchiral sorbent materials and commercial precoated layers used in chiral separations. Thus, it deals with silica gel native and esterified cellulose chiral plates (reversed phase plates impregnated with a chiral selector) and C-18, C-18W, diol, diphenyl, and C-2 chemically bonded silica gel. At the end of this chapter, the author discusses the quantification of enantiomers by using densitometry, depending on the type of the stationary phase employed. 

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