Electrospray ionization in concentrated acetonitrile vapor improves the performance of mass spectrometry for proteomic analyses

- Electrospray ionization is performed in the presence of concentrated ACN vapor.
- The background interferences are feasibly suppressed and the peptide signals are enhanced in ESI-MS analyses.
- The median MS signal intensity was improved 5 times for the 23 BSA tryptic peptides.
- The number of reproducibly and accurately quantified peptides could be improved 67% in six replicate label-free quantitative proteome analyses of cell line sample.

Suppressing the background interferences and enhancing the analytes signals are long-term goals in high performance electrospray ionization mass spectrometry (ESI-MS) analyses. We observed that performing electrospray in the presence of a concentrated acetonitrile atmosphere suppresses background interferences and enhances peptide signals. An enclosed nanoESI source was utilized to provide a stable atmosphere of concentrated acetonitrile vapor for high performance ESI-MS analyses. The median MS signal intensity increased by 5 times for a set of 23 BSA tryptic peptides in direct ESI-MS analysis. Further, the number of reproducibly and precisely quantified peptides could be improved 67% in six replicate label-free quantitative proteome analyses by this strategy.