Retention behaviour of some estradiol derivatives on alumina in normal phase chromatrography

The retention constants of variously substituted estradiol derivatives were measured as a function of the composition of various binary mobile phases in order to study the relationship between chemical structure and retention behaviour in TLC on alumina. The slopes and in rcepts of the linear relationships between the retention constant R M and the logarithm of the volume fraction of the polar mobile phase component were calculated and are discussed in relation to the characteristics of the solute and mobile phase. The R F values and relative retention ΔR M of the compounds depend largely on the retention behaviour of their substituents. The results obtained in this investigation are compared with the results of the same derivatives obtained in previous investigations on silica gel.