Acidic drugs capacity ratios

Table 9.2 Log k values of acidic and basic drugs, nrf represents a negative capacity ratio. Reproduced by permission of Elsevier, ref. 37.

The tetrahydrophthalic ester of prednisolone, an anti-inflammatory drug, consists of two diastereoisomers. Olszewska et al. [66] describes the effect of addition of an optically active compound (amino acids, cyclodextrins, camphosulfonic acid) on the capacity ratios, k, and separation factors of these diastereoisomers by TLC. They used both mobile phases containing a chiral additive and stationary phases impregnated with an optically active compound, for example, silica gel plates impregnated with amino acids. The best resolution was obtained by impregnation of the stationary phase with o-camphosulfonic acid and copper acetate, and use of dichloromethane-isopropanol (90+10, v/v) as mobile phase. The addition of chiral compound to the mobile phase had less effect on the resolution of diastereoisomers. 

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