Alternative mobile phases for enhanced chromatographic selectivity and increased sensitivity in peptide separations

Area of Science:

• Biochemistry
• Analytical Chemistry

Background:

• Standard peptide separation uses reversed-phase high-performance liquid chromatography (RP-HPLC) with acetonitrile and trifluoroacetic acid (TFA).
• Achieving optimal resolution in complex peptide mixtures often requires modifying mobile phase composition or employing complementary separation mechanisms.

Purpose of the Study:

• To investigate the effect of replacing trifluoroacetic acid (TFA) with dilute hydrochloric acid (HCl) in reversed-phase chromatography for peptide separation.
• To explore the utility of strong cation exchange (SCX) chromatography as a complementary technique for peptide mapping.

Main Methods:

• Separation of tryptic digests of cytochrome c using reversed-phase chromatography on a C18 column with dilute HCl as the mobile phase additive.
• Separation of the same digests using strong cation exchange chromatography on a Protein-Pak SP 8HR column.

Main Results:

• Replacing TFA with dilute HCl in reversed-phase chromatography yielded different and enhanced selectivity.
• Hydrochloric acid-based mobile phases offered increased optical clarity, leading to higher sensitivity at low ultraviolet wavelengths.
• Strong cation exchange chromatography provided significantly different selectivity compared to reversed-phase methods.
• The combined approach expanded options for peptide mapping, offering improved selectivity, mass sensitivity, and spectral information.

Conclusions:

• Dilute hydrochloric acid offers an effective alternative to trifluoroacetic acid in reversed-phase peptide separation, enhancing selectivity and sensitivity.
• Complementary use of reversed-phase and strong cation exchange chromatography provides broader peptide mapping capabilities.
• This approach increases analytical options for peptide characterization, particularly in the low ultraviolet range.