title: Direct ion imaging approach for investigation of ion dynamics in multipole ion guides.
abstract: A key requirement of electrospray ionization (ESI) and other techniques facilitating ionization at elevated pressures is the efficient transport of free gas-phase ions into the high vacuum region of the mass spectrometer. Radio frequency (RF) multipole ion guides that allow for collisional cooling are one of the most popular means of achieving this. However, their performance is highly dependent on several experimental factors, including pressure and various electrode potentials along the ion path. To experimentally visualize these effects, we have employed a position-sensitive detector at the exit of a quadrupole mass spectrometer (QMS) instrument operated in RF only mode that employs an RF only octopole as a collisional cooling ion guide. This allows the spatial distribution of the ions, and its dependence on experimentally determined conditions, to be directly visualized at the exit of the quadrupole. This investigation provides a detailed insight into the ion dynamics occurring inside multipole ion guides. This knowledge can directly be applied to instrument development and to improve the ion transmission efficiency and, thus, sensitivity. Numerical simulations using custom-developed trajectory simulation software are compared and contrasted with the experimental observations.
authors.affiliation: †FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands.|‡TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Sarfaraz U A H
authors.initials: SU
authors.lastname: Syed
authors.affiliation: §Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool, L69 3GJ, United Kingdom.
authors.forename: Simon
authors.initials: S
authors.lastname: Maher
authors.affiliation: †FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands.
authors.forename: Gert B
authors.initials: GB
authors.lastname: Eijkel
authors.affiliation: †FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands.|∥M4I, The Maastricht MultiModal Molecular Imaging Institute, Maastricht University, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands.
authors.forename: Shane R
authors.initials: SR
authors.lastname: Ellis
authors.affiliation: §Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool, L69 3GJ, United Kingdom.
authors.forename: Fred
authors.initials: F
authors.lastname: Jjunju
authors.affiliation: §Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool, L69 3GJ, United Kingdom.
authors.forename: Stephen
authors.initials: S
authors.lastname: Taylor
authors.affiliation: †FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands.|‡TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands.|∥M4I, The Maastricht MultiModal Molecular Imaging Institute, Maastricht University, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands.
authors.forename: Ron M A
authors.initials: RM
authors.lastname: Heeren