Calculation of the amino acid hydrophilicity index for retention of peptides separation in a normal-phase LC

It was reported in a previous paper that the separation of peptides took pl ace in normal-phase liquid chromatography on amide, diol and silica columns . In this study, the contribution of individual amino acid residues to the retention of peptides was evaluated in order to clarify the mechanism of pe ptide separation. This paper lists the "hydrophilicity retention coefficien ts". The retentions of 121 peptides were measured through normal-phase liqu id chromatography on the amide, diol and silica columns using an acetonitri le-water mixed solution containing 0.2% trifluoroacetic acid + 0.2% triethy lamine as the mobile phase in a linear gradient elution system. For the sil ica column, the best-fit hydrophilicity retention coefficients could be cal culated by a linear-regression analysis. For the amide and diol columns, th e best-fit hydrophilicity retention coefficients could be calculated by a n on-linear regression analysis. A set of the hydrophilicity retention coeffi cients on each column successfully explained the contribution degree of ret ention on each column.