Toward high pressure miniature protein mass spectrometer: Theory and initial results.

Current miniature mass spectrometers mainly focus on the analyses of organic and small biological molecules. In this study, we explored the possibility of developing high resolution miniature ion trap mass spectrometers for whole protein analysis. Theoretical derivation, GPU assisted ion trajectory simulation, and initial experiments on home-developed "brick" mass spectrometer were carried out. Results show that ion-neutral collisions have smaller damping effect on large protein ions, and a higher buffer gas pressure should be applied during ion trap operations for protein ions. As a result, higher pressure ion trap operation not only benefits instrument miniaturization, but also improves mass resolution of protein ions. Dynamic mass scan rate and generation of low charge state protein ions are also found to be helpful in terms of improving mass resolutions. Theory and conclusions found in this work are also applicable in the development of benchtop mass spectrometers.