Patent ID: 8426155

Claim:
A method for the mass spectrometric analysis of a protein mixture in a mass spectrometer containing an RF ion trap, comprising: (a) digesting proteins of the protein mixture to form digest peptides; (b) separating the digest peptides by one of a chromatographic and electrophoretic process to elute digest peptides; (c) ionizing the eluting digest peptides with an ionization method producing multiply charged ions; (d) filling the RF ion trap with digest peptide ions having masses between a start mass (m/z) b and an end mass ((m/z) b +Δ(m/z)) forming a mass window; (e) reducing the charge of the peptide ions by introducing reactant ions into the RF ion trap wherein the m/z values of the charge-reduced peptide ions are shifted out of the mass window; (f) separating the ions with m/z values remaining in the mass window from those ions whose m/z values lie outside the window; and (g) acquiring a mass spectrum of the charge-reduced peptide ions.