EFFECT OF COLUMN TEMPERATURE ON RETENTION OF DIPEPTIDE ISOMERS IN REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

The effect of column temperature on the capacity factor and selectivity of dipeptide isomers was investigated. It has been observed that the variation in the logarithm of the capacity factor of dipeptide isomers is linearly dependent on the reciprocal of the absolute column temperature. The standard enthalpic change for dipeptide isomers is almost a constant, and the selectivity value is almost independent of the column temperature. It can be concluded that (1) the enthalpy change of dipeptide isomers in RP-HPLC is mainly determined by the molecular interaction in the mobile phase and (2) the difference of their standard entropy change play more important role in the selectivity value than that of standard enthalpy change does