Nanopore ion sources deliver single amino acid and peptide ions directly into high vacuum

In this talk, we describe a nanopore ion source for mass spectrometry that delivers ions directly into high vacuum from aqueous solutions. The ion source comprises a pulled quartz capillary with a sub-100 nm opening. Ions escape from the electrified meniscus between the liquid and high vacuum by the mechanism of ion evaporation and travel along collisionless trajectories into the ion detector. We present mass spectra for 16 different amino acid ions as well as post-translationally modified variants of glutathione in unsolvated states, obtained using the nanopore ion source. The current emanating from the source is composed of ions rather than charged droplets, and more than 90 % of the current can be recovered in a collector at the far end of the instrument. The nanopore ion source could enable more sensitive proteomic analyses. It circumvents the sample loss mechanisms inherent to conventional electrospray ionization (ESI), where charged droplets are sprayed into a background gas that scatters ions and degrades their transmission.