title: Optimizing electrospray interfaces using slowly diverging conical duct (ConDuct) electrodes.
abstract: We demonstrate that the efficiency of ion transmission from atmosphere to vacuum through stainless steel electrodes that contain slowly divergent conical duct (ConDuct) channels can be close to 100%. Here, we explore the properties of 2.5-cm-long electrodes with angles of divergence of 0°, 1°, 2°, 3°, 5°, 8°, 13°, and 21°, respectively. The ion transmission efficiency was observed to jump from 10-20% for the 0° (straight) channels to 90-95% for channels with an angle of divergence as small as 1°. Furthermore, the 2-3° ConDuct electrodes produced extraordinarily low divergence ion beams that propagated in a laser-like fashion over long distances in vacuum. To take advantage of these newly discovered properties, we constructed a novel atmosphere-to-vacuum ion interface utilizing a 2° ConDuct as an inlet electrode and compared its ion transmission efficiency with that of the interface used in the commercial (Thermo Fisher Scientific, San Jose, CA, USA) Velos Orbitrap and Q Exactive mass spectrometers. We observed that the ConDuct interface transmitted up to 17 times more ions than the commercial reference interface and also yielded improved signal-to-noise mass spectra of peptides. We infer from these results that the performance of many current atmosphere-to-vacuum interfaces utilizing metal capillaries can be substantially improved by replacing them with 1° or 2° metal ConDuct electrodes, which should preserve the convenience of supplying ion desolvation energy by heating the electrode while greatly increasing the efficiency of ion transmission into the mass spectrometer.
authors: Laboratory for Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, NY, 10065, USA.
authors: Andrew N
authors: AN
authors: Krutchinsky
authors: Júlio C
authors: JC
authors: Padovan
authors: Herbert
authors: H
authors: Cohen
authors: Brian T
authors: BT
authors: Chait
mesh_terms: D004566:Electrodes; D004867:Equipment Design; D007477:Ions / Q000032:analysis / Q000737:chemistry; D007553:Isotope Labeling; D010446:Peptide Fragments / Q000032:analysis / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation* / Q000379:methods*; D013193:Stainless Steel; D014618:Vacuum
chemical_list: D007477:Ions; D010446:Peptide Fragments; D013193:Stainless Steel