Infrared ion spectroscopy inside a mass‐selective cryogenic 2D linear ion trap

Abstract

We demonstrate operation of the first cryogenic 2D linear ion trap (LIT) with mass-selective capabilities. This trap presents a number of advantages for infrared ion “action” spectroscopy studies, particularly those employing the “tagging/messenger” spectroscopy approach. The high trapping efficiencies, trapping capacities, and low detection limits make 2D LITs a highly suitable choice for low-concentration analytes from scarce biological samples. In our trap, ions can be cooled down to cryogenic temperatures to achieve higher-resolution infrared spectra, and individual ions can be mass selected prior to irradiation for a background-free photodissociation scheme. Conveniently, multiple tagged analyte ions can be mass isolated and efficiently irradiated in the same experiment, allowing their infrared spectra to be recorded in parallel. This multiplexed approach is critical in terms of increasing the duty cycle of infrared ion spectroscopy, which is currently a key weakness of the technique. The compact design of this instrument, coupled with powerful mass selection capabilities, set the stage for making cryogenic infrared ion spectroscopy viable as a bioanalytical tool in small molecule identification.

Identification of Active Sites and Structural Characterization of Reactive Ionic Intermediates by Cryogenic Ion Trap Vibrational Spectroscopy

“…While it remains challenging to measure the absorption of photons by mass‐selected gaseous ions directly, because the attainable number density of larger ions is typically too small to attenuate the photon flux sufficiently, significant advances have been made in developing and improving methods for the indirect detection of photoabsorption by cold, mass‐selected cluster ions using IR action spectroscopy, over the last twenty years . Of these methods, cryogenic ion trap vibrational spectroscopy has emerged as the most generally applicable . Cryogenic ion traps do not only allow for a thermalization of the trapped ions close to the ambient temperature, but also provide an alternative method for the formation of messenger‐complexes .…”

“…[20][21][22][23] Of thesem ethods,c ryogenic ion trap vibrational spectroscopy [20] has emerged as the most generally applicable. [24][25][26][27][28][29][30][31][32][33][34] Cryogenic ion traps [35,36] do not only allow for at hermalization of the trapped ions close to the ambient temperature, buta lso provide an alternative methodf or the formation of messenger-complexes. [37] Separating the cluster formation process( in the ion source region) from the tagging process (in the ion trap region) has far-reaching consequences.…”

Mass spectrometry in drug metabolism and pharmacokinetics: Current trends and future perspectives

“…IR spectra were generated from less than 10 ng of metabolite obtained from a collected HPLC fraction. IR‐IS performed at cryogenic temperatures can result in improved spectral resolution and/or faster duty cycles and might be the way forward for bioanalytical applications.…”

Operation and Performance of a Mass-Selective Cryogenic Linear Ion Trap

“…Recently, we demonstrated IR spectroscopy results from the first mass-selective cryogenic 2D linear ion trap (cryoLIT) [39]. The rectilinear electrodes of this design combine simplicity in machining with the higher trapping efficiencies and capacities of 2D linear ion traps vis-à-vis 3D ion traps [40–43].…”

“…Cryogenic operation of Fourier transform ion cyclotron resonance (FTICR) traps has already been demonstrated [36, 37]; however, due to the image current detection scheme, these are generally less sensitive than rf traps [38]. Recently, we demonstrated IR spectroscopy results from the first mass-selective cryogenic 2D linear ion trap (cryoLIT) [39]. The rectilinear electrodes of this design combine simplicity in machining with the higher trapping efficiencies and capacities of 2D linear ion traps vis-à-vis 3D ion traps [40–43].…”