Isomer-Specific Two-Color Double-Resonance IR²MS³ Ion Spectroscopy Using a Single Laser: Application in the Identification of Novel Psychoactive Substances

Abstract

The capability of an ion trap mass spectrometer to store ions for an arbitrary amount of time allows the use of a single infrared (IR) laser to perform two-color double resonance IR–IR spectroscopic experiments on mass-to-charge ( m / z ) selected ions. In this single-laser IR 2 MS 3 scheme, one IR laser frequency is used to remove a selected set of isomers from the total trapped ion population and the second IR laser frequency, from the same laser, is used to record the IR spectrum of the remaining precursor ions. This yields isomer-specific vibrational spectra of the m / z -selected ions, which can reveal the structure and identity of the initially co-isolated isomeric species. The use of a single laser greatly reduces the experimental complexity of two-color IR 2 MS 3 and enhances its application in fields employing analytical MS. In this work, we demonstrate the methodology by acquiring single-laser IR 2 MS 3 spectra in a forensic context, identifying two previously unidentified isomeric novel psychoactive substances (NPS) from a sample that was confiscated by the Amsterdam Police.

Advanced tandem mass spectrometry in metabolomics and lipidomics—methods and applications

“…Another benefit of action spectroscopy experiments is the combination of sequential CID/IRMPD and IRMPD spectroscopy to structurally interrogate fragment or remaining precursor ions. As shown by Martens et al [135] and von Geenen et al [25], fragmentation of isomeric dicarboxylic acids and fluoromethamphetamines (Fig. 1) followed by IRMPD spectroscopy allows to deduce precursor and fragment structures.…”

“…1-dashed box). Although fluorine position isomers are separated in GC runs, EI-MS spectra of these isomers are virtually indistinguishable [25]. To overcome these issues, researchers have developed bioinformatic tools that use fragmentation rules [26], predict metabolite CID-MS n spectra [27,28], or use deep neuronal networks to assign mass spectrometric features to metabolite groups or specific compounds [21].…”

Evaluation of table-top lasers for routine infrared ion spectroscopy in the analytical laboratory

“… 62 Additionally, precursor ion depletion curves were obtained by recording the normalized precursor ion intensity (1 – IRMPD yield) as a function of irradiation time using an automated protocol described in ref. 34 .…”

Infrared multiple photon dissociation (IRMPD) spectroscopy and its potential for the clinical laboratory

“…IRMPD spectroscopy has been used for the characterization and identification of street drugs. In one study, the novel psychoactive substances (NPSs) of a street sample were subjected to IRMPD spectroscopy, where the active compounds were identified as 2- and 4-flouromethamphetamine (FMA), and the presence of 3-fluoromethamphetamine was ruled out [87] . Specifically, in this study, an approach dubbed “IR 2 MS 3 ”, based on hole-burning (setting the laser at one specific frequency to “burn away” one type of conformer/structure), was implemented.…”