Absorption Mode Fourier Transform Electrostatic Linear Ion Trap Mass Spectrometry

Abstract

In Fourier transform mass spectrometry, it is well-known that plotting the spectrum in absorption mode rather than magnitude mode has several advantages. However, magnitude spectra remain commonplace due to difficulties associated with determining the phase of each frequency at the onset of data acquisition, which is required for generating absorption spectra. The phasing problem for electrostatic traps is much simpler than for Fourier transform ion cyclotron resonance (FTICR) instruments, which greatly simplifies the generation of absorption spectra. Here, we present a simple method for generating absorption spectra from a Fourier transform electrostatic linear ion trap mass spectrometer. The method involves time shifting the data prior to Fourier transformation in order to synchronize the onset of data acquisition with the moment of ion acceleration into the electrostatic trap. Under these conditions, the initial phase of each frequency at the onset of data acquisition is zero. We demonstrate that absorption mode provides a 1.7-fold increase in resolution (full width at half maximum, fwhm) as well as reduced peak tailing. We also discuss methodology that may be applied to unsynchronized data in order to determine the time shift required to generate an absorption spectrum.

Phase relationships in two-dimensional mass spectrometry

“…Absorption mode FT-ICR MS has shown particular promise for complex mixture analysis such as the study of proteins, crude oil, and lignin [40][41][42][43]. Phase correction for absorption mode FTMS has also been developed for Orbitraps and electrostatic linear ion traps [44,45].…”

Isotope-resolved photodissociation pathways of lead-doped bismuth clusters from tandem multi-reflection time-of-flight mass spectrometry

“…In nuclear physics, MR-ToF devices have recently been applied for fast mass separation or ion selection [22,23] as well as precision mass measurements [24]. On the molecular level, they are appreciated for their capability as ion traps with a virtually unrestricted mass range, operated either in "non-bunching mode," where injected ion beams fill the entire trap volume [25,26], or with capacitive pickup detection (Fourier transform MR-ToF) for high-resolution mass spectrometry [27][28][29][30].…”

Realistic modeling of ion-neutral collisions in quadrupole ion traps

“…Compared with field imperfection and space charge effects, ion‐neutral collision could be the major ion motion decay factor in a quadrupole ion trap, which operates at a relatively high pressure region (mTorr). Therefore, it is critical to have an analytical expression of the ion motion decay profile, so that the collision cross section could be calculated from the spectral line width obtained from FT ion trap instruments . With the pseudo‐potential approximation, the analytical solution of ion motion within quadrupole ion traps was only found for ion motions with the Langevin collision model, which greatly limits the application of ion collision cross section measurement methods.…”

“…Therefore, it is critical to have an analytical expression of the ion motion decay profile, so that the collision cross section could be calculated from the spectral line width obtained from FT ion trap instruments. [36][37][38][39][40][41][42] With the pseudo-potential approximation, the analytical solution of ion motion within quadrupole ion traps was only found for ion motions with the Langevin collision model, which greatly limits the application of ion collision cross section measurement methods.…”