Optimization by isochronal analysis I. Changes in mobile phase composition and velocity

Summary  The theory of isochronal analysis (time normalization) has been extended to reversed-phase liquid chromatography. Of the possible manipulation of experimental parameters, the present paper develops a framework for optimizing the resolution by the simultaneous change of mobile phase velocity and composition. For that purpose the resolution equation was written in terms of these two parameters and under the constraint of constant analysis time. This treatment allows plotting the resolution versus the mobile phase composition and velocity. The surfaces thus obtained show the changes that the analyst must perform in order to optimize the resolution. The treatment deals with three possible α dependencies on the amount of organic modifier: constant, increasing and decreasing.