Ion sources for mass spectrometric identification and imaging of molecular species

Abstract

Covering: 2013 The ability to transfer molecular species to the gas phase and ionize them is central to the study of natural products and other molecular species by mass spectrometry (MS). MS-based strategies in natural products have focused on a few established ion sources, such as electron impact and electrospray ionization. However, a variety of other ion sources are either currently in use to evaluate natural products or show significant future promise. This review discusses these various ion sources in the context of other articles in this special issue, but is also applicable to other fields of analysis, including materials science. Ion sources are grouped based on the current understanding of their predominant ion formation mechanisms. This broad overview groups ion sources into the following categories: electron ionization and single photon ionization; chemical ionization-like and plasma-based; electrospray ionization; and, laser desorption-based. Laser desorption-based methods are emphasized with specific examples given for laser desorption postionization sources and their use in the analysis of intact microbial biofilms. Brief consideration is given to the choice of ion source for various sample types and analyses, including MS imaging.

Intraspecific variations in Conus purpurascens injected venom using LC/MALDI-TOF-MS and LC-ESI-TripleTOF-MS

“…Some ions are detected in one ionization technique that are not detected in the other, giving rise to different sets of masses identified by MALDI-TOF-MS vs. ESI-TripleTOF-MS. The differences in the detected masses might be due to spectra that only show major components, whereas other peptides in the mixture are not detected due to poor ionization, or their abundance fall below the dynamic range capabilities of the instrument [55]. This may explain why less masses were detected using MALDI-TOF-MS in comparison to LC-ESI-TripleTOF-MS [56], and shows that the overlapping capabilities of different ion sources must be used to detect the most compounds possible in complex samples.…”

Gas chromatography coupled to atmospheric pressure ionization mass spectrometry (GC-API-MS): Review

“…In both ion sources the APPI process occurs within the confined volume of a capillary, but differs in the types of VUV source and whether or not they employ a VUV window. Both ion sources are specifically designed for coupling to chromatographic interfaces, and displayed improved ion transmission to the MS and reduction in unfavorable ion-molecule reactions [81]. Capillary APPI is well suited to the analysis of volatile compounds.…”

“…Capillary APPI is well suited to the analysis of volatile compounds. CPI detects both volatile and nonvolatile compounds regardless polarity, since it provides additional sample heating [55,81].…”

MALDI Mass Spectrometry Imaging for the Simultaneous Location of Resveratrol, Pterostilbene and Viniferins on Grapevine Leaves

“…The relative intensities of fragments are indicated in parenthesis. (20) ; 411 (10) ; 369 (12) (38) ; 347 (40) ; 333 (50) ; 317 (14) ; 307 (20) ; 267 (12) ; 251 (13) (38) ; 159 (32) ; 157 (29) ; 143 (11) The extraction sample of grapevine leaf irradiated by UV was also investigated by MALDI-TOFMS with DHB as the matrix (and 0.1% of TFA). The average mass spectrum obtained from 50 mass spectra is displayed in the Figure 2.…”

“…Indeed, MSI is able to provide a specific spatial distribution of proteins or metabolites in tissues. Depending on the ion source, the sample preparation and the mass spectrometer used, the spatial distribution of molecules on a plant sample is specifically dedicated to some compound families [10,11].…”