Nonchiral Plates Used with Chiral Mobile Phases

3 NONCHIRAL PLATES USED WITH CHIRAL MOBILE PHASES 

Direct separations of enantiomers have been made using a variety of commercial achiral precoated TLC and HPTLC plates developed with a chiral mobile phase. 

Thin Layer Chromatography in Chiral Separations and Analysis 

The layers used include unmodified silica gel (described in Section 3.2.3) and C-2 (dimethyl), C-18 (octadecyl), C-18W, diol, and diphenyl chemically bonded silica gel. 

Diol plates are prepared by reaction of the silica matrix with a silane derived from glycerol. The resulting alcoholic hydroxyl residues bonded to the silica by a propyl spacer can operate with NP- or RP-TLC mechanisms, depending on the mobile phase and solutes. Polar compounds show reasonable retention by hydrogen bond and dipole-type interactions in the former mode, and in the RP mode retention is low but higher than with amino layers. 

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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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