Retention behavior of peptides in hydrophilic-interaction chromatography

Selected hydrophilic interaction chromatography (HILIC) columns packed with bare silica, bridge-ethyl hybrid silica, or an amide sorbent chemistry were utilized for an investigation of chromatographic behavior and separation selectivity of tryptic peptides. Retention model was proposed allowing for retention prediction of peptides with correlation coefficient R(2)~0.92-0.97 for various columns. The values of optimized amino acid retention coefficients were compared to those obtained for reversed-phase liquid chromatography (Gilar et al., Anal. Chem. 2010, 82, 265-275) and used to elucidate the impact of different amino acid on peptide HILIC retention. In contrast to reversed-phase chromatography, where presence of Phe, Trp, Ile, and Leu amino acid residues in sequence strongly promoted, and presence of hydrophilic His, Lys and Arg residues strongly reduced peptide retention, the effects of these amino acid residues in HILIC were opposite (His, Lys and Arg promote, Phe, Trp, Ile and Leu demote peptide retention in HILIC). Retention coefficient optimized for pH experiments illustrated the impact of silanols on HILIC retention.