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

Abstract

We report on the performance of a cryogenic 2D linear ion trap (cryoLIT) that is shown to be mass-selective in the temperature range of 17-295 K. As the cryoLIT is cooled, the ejection voltages during the mass instability scan decrease, which results in an effective mass shift to lower m/z relative to room temperature. This is attributed to a decrease in trap radius caused by thermal contraction. Additionally, the cryoLIT generates reproducible mass spectra from day-to-day, and is capable of performing stored waveform inverse Fourier transform (SWIFT) mass isolation of fragile N-tagged ions for the purpose of background-free infrared dissociation spectroscopy. Graphical Abstract ᅟ.

Applications of Infrared Multiple Photon Dissociation (IRMPD) to the Detection of Posttranslational Modifications

“…Among the most fruitful and promising achievements realized in this context, one should acknowledge cryogenic vibrational spectroscopy. ,− As initially proposed by Gerlich, most of the setups are based on a cryogenically cooled multipole ion trap. Molecular ions are cooled through multiple collisions with a buffer gas, − thus reducing the thermal energy distribution of the sampled ionic species and thereby improving the spectroscopic resolution. Sensitivity improvement is achieved using the “messenger technique”. ,− This technique relies on the formation of weakly bound ion-neutral complexes, where the neutral species, also called tag, is typically a rare gas or H 2 .…”

Quantum Chemistry Calculations for Metabolomics

“…Other works without coupled ion mobility have also shown the value of quantum chemical calculations for molecular and conformer identification with the use of conformer-selective cryogenic IR spectroscopy. 275 , 281 , 282 …”

“…Of significant importance to the small-molecule identification field is the recent advancement of cryogenic IRIS, spearheaded by groups at the Swiss Federal Institute of Technology Lausanne and University of Florida, led by Professors Thomas Rizzo ,,− and Nicolas Polfer, − respectively. If the ultimate goal of IR spectroscopy is to determine structural information on a molecule, the highest resolution (and highest deconvolution) can be obtained by reducing thermal inhomogeneous broadening and conformational heterogeneity .…”

“…Interestingly, the trans -Pro 2 / trans -Pro 3 isomer geometry is also that which is observed in solution via NMR and implies that the solution structure maintains its geometry during ESI. Other works without coupled ion mobility have also shown the value of quantum chemical calculations for molecular and conformer identification with the use of conformer-selective cryogenic IR spectroscopy. ,, …”

UV‐vis spectroscopy of gas‐phase ions

“…The performance of a single ion trap, when used for all ion manipulations, has been shown to be adversely affected by the thermal contraction of the trap electrodes at low temperatures (17 K), which resulted in mass‐scale shifts. This effect has been shown to be more significant at higher m / z values and its correction required a careful recalibration of the mass scale (Tesler et al, 2018). Hence, low‐temperature UVPD measurements have been performed in a tandem set up, whereby the cold ion trap was used to store the ions to be photodissociated, while mass analysis of photofragment ions was accomplished after ejecting all ions to be accelerated and separated by a time‐of‐flight mass analyzer.…”