Premium
Fundamental aspects of electrospray droplet impact/SIMS
Author(s) -
Hiraoka Kenzo,
Mori Kunihiko,
Asakawa Daiki
Publication year - 2006
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.1048
Subject(s) - chemistry , analytical chemistry (journal) , mass spectrometry , ambient ionization , quadrupole mass analyzer , ionization , ion , desorption , secondary ion mass spectrometry , electrospray ionization , fragmentation (computing) , ion source , gramicidin , desorption electrospray ionization , electrospray , chromatography , chemical ionization , organic chemistry , biochemistry , adsorption , membrane , computer science , operating system
A new ionization method, electrospray droplet impact ionization (EDI), has been developed for matrix‐free secondary‐ion mass spectrometry (SIMS). The charged droplets formed by electrospraying 1 M acetic acid aqueous solution are sampled through an orifice with a diameter of 400 µm into the first vacuum chamber, transported into a quadrupole ion guide, and accelerated by 10 kV after exiting the ion guide. The droplets impact on a dry solid sample (no matrix used) deposited on a stainless steel substrate. The secondary ions formed by the impact are transported to a second quadrupole ion guide and mass‐analyzed by an orthogonal time‐of‐flight mass spectrometer (TOF‐MS). Ten pmol of gramicidin S could be detected with the presence of as much as 10 nmol of NaCl. The ion signal for arginine disappeared with decrease in the substrate temperature below 150 K owing to the formation of ice film over the sample surface. While 10 fmol of gramicidin S could be detected for 30 min, the ionization/desorption efficiency for EDI becomes smaller with an increase in the molecular weight (MW) of a biological sample. The largest protein samples detected to date are cytochrome c and lysozyme. The high sensitivity for EDI is due to the fact that samples only a few monolayers thick are subject to desorption/ionization by EDI, with little fragmentation. A coherent phonon excitation may be the main mechanism for the desorption/ionization of the solid sample. Copyright © 2006 John Wiley & Sons, Ltd.