Enhanced analysis of poly(ethylene glycols) and peptides using thermospray mass spectrometry

The effects of a needle-tip repeller electrode on thermospray mass spectra of poly(ethylene glycols) and peptide samples have been studied. A significant increase in ion current was observed for increased repeller potentials in the low-mass region (m/z 300 to m/z 1100) and the high-mass region (m/z 1100 to m/z 1900). The change in ion current is due to a change in ion extraction efficiency because of increased ion diffusion rates. The amount of peptide sample needed for direct injection studies was decreased 1 to 2 orders of magnitude by using an ion source with both a needle-tip repeller electrode and a restricted vaporizer probe tip.