Stability constants, cyclodextrins mobile phases

Aqueous a-cyclodextrin solutions seem to be generally applicable for TLC separation of a wide variety of substituted aromatics on polyamide thin-layer stationary sheet (13-14). In most cases, the compounds moved as distinct spots and their R, values were dependent on the concentration of the cyclodextrin in tne mobile phase. In a given family of compounds, (o-, m-, and p-nitrophenols, for example) the isomer with the largest stability constant for a-cyclodextrin complex formation had the larger value. In general, the para-substituted isomers have larger R values than the meta-isomers, which in turn have larger R values than the ortho substituted ones. 

Numerous chromatographic studies have also been carried out to investigate possible applications of CyDs as multifunctional drug carriers, discussed in more detail in Chapters 14 and 15. For example the retention of psoralen derivatives was investigated on a C-18 column with HP-) -cyclodextrin as mobile phase additive [62]. Assuming 1 1 stoichiometry, in a 52 48 (v/v) methanol water mixture and temperature —5 °C, the corresponding stability constants were 30, 75, and 40 for the complexes of 8-methoxypsoralen, 5-methoxypsoralen and trimethylpsoralen with HP-yS-CyD, respectively. 

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