The micro-electrospray ionization source has been optimized for the specific analysis of neuropeptides such as neurotensin and methionine enkephalin. The source has the option of integrating nanoliter flow-rate desalting and preconcentration techniques into the micro-electrospray spray needle, eliminating post-column dead volumes. For neurotensin, the most sensitive neuropeptide analyzed thus far in this work, the injection of 10 μL of a solution containing 320 zeptomolesy/gmL gave an [M + 3H]+3 ion at m/z 558.4 with S/N of > 8:1. The MS/MS analysis of this peptide for the fragment ion at m/z 578.9 gave a S/N > 20:1 for a solution containing 32 attomoles/μL. © 1994 American Society for Mass Spectrometry.
Andren, P. E., Emmett, M. R., & Caprioli, R. M. (1994). Micro-Electrospray: Zeptomole/attomole per microliter sensitivity for peptides. Journal of the American Society for Mass Spectrometry, 5(9), 867–869. https://doi.org/10.1016/1044-0305(94)87010-1