Massive cluster impact mass spectrometry: A new desorption method for the analysis of large biomolecules

A new ion desorption method is described that utilizes a primary beam of massive, multiply charged cluster ions to generate secondary ions of peptides in a glycerol matrix. The massive cluster ion beam is generated via electrohydrodynamic emission using a 1.5 M solution of ammonium acetate in 30% aqueous glycerol. Negaitve ion spectra of peptides obtained using this technique show greatly decreased relative intensities for fragment ions and ‘chemical noise’ background when compared to spectra obtained using a xenon atom primary beam. The near absence of fragmets derived from radiation damage to the sample solution is attributed to the impact of primary particles with energies less than 1 eV/nucleon.