New ionization processes and applications for use in mass spectrometry

Abstract

Mass spectrometry (MS) continues to improve at a rapid pace as most prominently witnessed for mass analyzers and fragmentation technology. Ionization methods have also seen resurgence with ambient ionization approaches gaining a foothold because they often provide a convenient and direct means of sample analysis. Nevertheless, a vast majority of biological analyses using MS apply electrospray ionization or matrix-assisted laser desorption/ionization, methods introduced in the 1980s, or variants thereof. To further advance applications by MS such as protein characterization, and, for example, addressing their location within specific cell types, the progress in mass analyzer and fragmentation technology needs to be matched with similar advances in ionization technology. It is imperative to seek ionization methods that more efficiently convert molecules, to gas-phase ions in a way that allows high transfer efficiency to the mass analyzer and subsequently the detector to achieve a more complete picture of sample composition. This review provides a snapshot of fundamental aspects of new ionization methods and potential biological and medical applications.

Transmission Geometry Laserspray Ionization Vacuum Using an Atmospheric Pressure Inlet

“…The airtight Cone B (Figure 1III.A, green plot lines) provided the lowest analyte ion abundance for all matrices when compared to Cones A (Figure 1III.A, red plot lines) and C (Figure 1III.A, blue plot lines) suggesting the importance of air flow in ion transmission and possibly aiding the ionization process. 3,12 This might be expected since the Z-Spray source is designed to operate with rather high gas flow. The representative mass spectra (Figure 1III.B) are shown corresponding to the highest ion intensity of the [M + 5H] 5+ charge state observed for bovine insulin using each matrix.…”

“…2 This relates well with the hypothesis that “desolvation” of the charged matrix/analyte clusters is necessary to expose bare analyte ions. 3,12 …”

“…14 The energy contained in the matrix is sufficient for analyte ionization and has been discussed to be related to luminescence characteristics of the small molecule compound. 12,14 This matrix has been shown to produce multiply charged analyte ions when introduced to a vacuum using an intermediate pressure MALDI source 14 or directly from atmospheric pressure into an inlet aperture. 15 Even though a laser is not necessary for ionization using 3-NBN as matrix, there are applications where use of a laser is desirable, such as sampling small areas and in imaging studies.…”

Desorption electrospray ionization-high resolution mass spectrometry for the screening of veterinary drugs in cross-contaminated feedstuffs

“…Further droplets hit this film splashing secondary droplets containing the analytes into the mass spectrometer [24]. Since their introduction, ambient techniques have been applied to multitude of fields, such as environmental [24][25][26], food [27][28][29], clinical diagnosis [30], and forensic analysis [31]. Nevertheless, only few papers described the use of ambient techniques for the analysis of veterinary drugs [32,33].…”

Characterizing synthetic polymers and additives using new ionization methods for mass spectrometry

“…This method, termed solvent assisted ionization inlet (SAII), introduces samples directly from solution without the use of organic matrix compounds . These combined methods are now termed inlet ionization and are governed by the presence of a heated inlet, preferentially capillary, connecting atmospheric pressure to the vacuum of the mass spectrometer …”