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.