Liquid ion exchangers in reversed-phase systems for chromatography of steroidal glucosiduronic acids

Steroidal glucosiduronic acids were chromatographed on paper by the reversed-phase technique using five different liquid ion exchangers as stationary phase and aqueous KCl as mobile phase. The relationship of mobility of the acids (Rm) to both the amount of exchanger on the paper and the concentration of KCl in the mobile phase is discussed: the relationships may be expressed as Rm=n.log [exchanger] + const. and RM=-N.LOG [KCl] + const., respectively. Migration of the acids in the presence of different exchangers is correlated by use of the equation Rm (exchanger Y)=a.Rm (exchanger X) + b. The lack of appreciable correlation between migration of the acids in a reversed-phase system and a corresponding straight-phase system is discussed and expressed by means of regression equations. The correlation coefficients and standard errors of estimate from these equations provide useful indices for selecting two solvent systems that are to be used sequentially to obtain maximal resolution of a group of compounds. deltaRm values obtained for various functional groups with reversed-phase and straight-phase techniques are compared.