Calculation of peptide retention coefficients in normal-phase liquid chromatography.

The retention of 121 peptides was studied on a TSK Amide-80 column using solutions containing 0.1% trifluoroacetic acid and an increasing linear gradient of water in acetonitrile. The contribution of each residue to retention was calculated by linear multiple regression analysis. This paper described the contribution values 'hydrophilicity retention coefficients'. The result is an index of hydrophilicity retention coefficients for normal-phase liquid chromatography, analogous to the hydrophobicity indices calculated for the reversed-phase liquid chromatography. The order of residues in the index of one mode was substantially the inverse of the others'. Using the new hydrophilicity retention coefficients, retention times could be predicted for peptides of known amino acid content and sequence.