Article

The Utility of Surface-Induced Dissociation in Molecular Identification

Surface Analysis Spotlight: TOF-SIMS

by Greg Fisher Principal Scientist

Tandem mass spectrometry (tandem MS, or MS/MS) has been in use for several decades for the accurate identification of molecules. Compositional identification of molecules by tandem MS is frequently accomplished by breaking the precursor molecules into substituent components via collisional activation at kinetic energies of < 200 electron volts (eV), a process generally referred to as collision-induced dissociation (CID). Adding to the power of tandem MS, kilo-electron volt CID (keV-CID) allows for the structural elucidation of molecules, metabolites, and degradation products, and this can be achieved with mass spectrometry imaging (MSI) for 2D/3D molecular visualization. TOF-SIMS tandem MS imaging has been particularly useful in a broad range of applications including single cell-omics, metabolomics, natural product chemistry, pharmaceutical research, high-performance polymers and composites, 2D materials, electronic devices, catalysis, forensics, and failure analysis.

Within this context, the focus of this lecture is on introducing and exploring the advantages of surface-induced dissociation (SID) to aid in molecular identification alongside CID spectra. Unlike CID, which promotes cleavage at every molecular bond, SID is more subtle, leading to the observation of functional group chemistry, as demonstrated in Figure 1. Although both the SID and the CID spectra were generated at the same kinetic energy, the molecular energetics and relaxation pathways are distinct, which can significantly impact spectral calibration and the identification of precursor peaks

Figure 1: Tandem MS spectra of the crystal violet [M-Cl]⁺ quasi-molecular ion, m/z 372, produced by collision-induced dissociation (CID, panel A, top) and surface-induced dissociation (SID, panel B, bottom) by collisional activation at a kinetic energy of 1.55 keV. See the article G.L. Fisher et al., Anal. Chem. 88 (2016) 6433-6440 for full experimental details.

For more information on how surface analysis is exploring the advantages of surface-induced dissociation (SID) to aid in molecular identification alongside CID spectra., please attend the upcoming SIMS Europe 2023 where Dr. Greg Fisher, Principal Scientist is invited to give a talk on "The Utility of Surface-Induced Dissociation in Molecular Identification."