Solvatochromic parameter values and pH in acetonitrile-water mixtures. Optimization of mobile phase for the separation of peptides by high-performance liquid chromatography.

The proportion of the organic modifier and the pH of the mobile phase were optimized in order to separate a series of low-molecular-mass peptides by HPLC. The composition of the mobile phase was optimized by establishing relationships between retention parameters and Reichardt's ENT scale of solvent polarity, and between retention and the Kamlet-Taft multiparameter solvent scale of the eluent, using linear solvation energy relationships (LSER). The pH of the mobile phase was also successfully optimized by establishing relationships between the retention and the pH measured in the aqueous-organic mixture used as eluent.