Ion Desorption Efficiency and Internal Energy Transfer in Carbon-Based Surface-Assisted Laser Desorption/Ionization Mass Spectrometry: Desorption Mechanism(s) and the Design of SALDI Substrates

Abstract

Ion desorption efficiency and internal energy transfer were probed and correlated in carbon-based surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using benzylpyridinium (BP) salt as the thermometer chemical. In a SALDI-MS experiment with a N(2) laser (at 337 nm) used as the excitation light source and with multiwalled carbon nanotubes (CNT), buckminsterfullerene (C(60)), nanoporous graphitic carbon (PGC), non-porous graphite particles (G), highly oriented pyrolytic graphite (HOPG), or nanodiamonds (ND) as the SALDI substrate, both the desorption efficiency in terms of ion intensity of BP and the extent of internal energy transfer to the ions are dependent on the type and size of the carbon substrates. The desorption efficiency (CNT approximately C(60) > PGC > G > HOPG > ND) in general exhibits an opposite trend to the extent of internal energy transfer (CNT < C(60) approximately PGC < G approximately HOPG < ND), suggesting that increasing the extent of internal energy transfer in the SALDI process may not enhance the ion desorption efficiency. This phenomenon cannot be explained by a thermal desorption mechanism, and a non-thermal desorption mechanism is proposed to be involved in the SALDI process. The morphological change of the substrates after the laser irradiation and the high initial velocities of BP ions (1100-1400 ms(-1)) desorbed from the various carbon substrates suggest that phase transition/destruction of substrates is involved in the desorption process. Weaker bonding/interaction and/or a lower melting point of the carbon substrates favor the phase transition/destruction of the SALDI substrates upon laser irradiation, consequently affecting the ion desorption efficiency.

Comparison of the internal energy deposition of direct analysis in real time and electrospray ionization time-of-flight mass spectrometry

“…To completely develop DART as a mature analytical tool for direct MS analysis, further research into the physicochemical processes governing ionization, ion transport, and activation is needed [7,9]. To date, the majority of internal energy (E int ) deposition studies have focused primarily on spray- [10 -12] and laser- [13,14] based desorption/ionization techniques. E int deposition studies of ions generated by APCI have focused on post-source E int contributions to fragmentation [15] or isomerization [16] during insource and tandem MS collision induced dissociation (CID).…”

A novel laser desorption/ionization method using through hole porous alumina membranes

“…To date a number of ionization techniques that belong to SALDI have been proposed,1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, ...…”

“…nanoparticles as typical, in treatable forms such as suspension liquids in order to ensure that the photon energies of the laser can act to desorp and ionize analytes 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45. Indeed, the soft ionization laser method such as the original form of MALDI also belongs to this category 1.…”

Nanomaterial-Assisted Laser Desorption Ionization for Mass Spectrometry-Based Biomedical Analysis

“…Tang et al investigated the relationship between ion desorption efficiency and internal energy transfer in carbonbased surface-assisted LDI, including carbon nanotubes, buckminsterfullerene (C 60 ), nanoporous graphitic carbon, nonporous graphite particles, highly oriented pyrolytic graphite and nanodiamonds. It was found that the desorption efficiency generally exhibits an opposite trend to the extent of internal energy transfer [52]. In this article, we mainly focus on the recent application in biomedical study of matrix-free LDI methods, especially some important progresses since 2006, including biomolecule qualitative and quantitative analysis, LDI-MS tissue imaging, nanoparticle-based enzyme immunoassays/DNA hybridization and LDI in source photo-reaction with biomolecules.…”