Collision cross section (CCS) measurement by ion cyclotron resonance mass spectrometry with short‐time Fourier transform

Abstract

The proposed method was successfully applied to determine the CCSs of fatty acids and polyalanines in a petroleum gas oil matrix. This technique can be used for simultaneous measurement of cross sections for many ions in congested spectra.

Advancing Orbitrap Measurements of Collision Cross Sections to Multiple Species for Broad Applications

“…While CCS measurements are typically performed using ion mobility (IM) spectrometers such as ones based on low field drift tubes, ,, alternative methods have been employed based on algorithms that estimate CCS from the signal decay rates in ion trapping analyzers either in the time or frequency domain. − Such approaches are generally based on the correlation between ion-neutral collision rates and cross sections, thus deriving insight from the decay of ion signals with time. − These types of alternative CCS measurements have been implemented using both high-resolution (ion cyclotron resonance (ICR) systems − and Orbitrap analyzers) and low-resolution (electrostatic linear ion trap) Fourier transform (FT) mass analyzers as well as a home-built charge detection mass spectrometer . CCS measurements were first reported using FT-ICR mass spectrometers several decades ago, − and a more recent strategy adapted for FT-ICR instruments developed a relationship between the full width half-maximum (FWHM) of the frequency domain peak (Δω) and CCS (σ) (eq ) derived from the hard-sphere collision model description of ion-neutral collisions. − , σ = normalΔ ω N v To establish this relationship, the ion’s speed ( v ) and the pressure within the ICR cell must also be defined, the latter of which was used to calculate the density of neutral gas molecules ( N ) . This method has been employed for determination of CCSs of a wide array of analytes ranging from small molecules ,, to proteins and more recently has been used to study structural changes upon binding of alkali metal ions to the peptide leucine enkephalin and a macrocyclic cryptand as well as measure CCSs of product ions generated from collisional activated dissociation of the complexes .…”

“…Additionally, many of the previously described methods relied on isolating a single charge state of an ion of interest in the mass spectrometer per experiment, therefore limiting throughput. Other new data processing techniques have reported simultaneous measurement of CCS of small molecules in low charge states on FT-ICR platforms. , …”

“…Other new data processing techniques have reported simultaneous measurement of CCS of small molecules in low charge states on FT-ICR platforms. 24,34 Here we develop and evaluate alternate computational methods with the goal of estimating CCS from commonly available mass spectra files instead of transients on an Orbitrap mass spectrometer. To accomplish this goal, we compare the FWHM and direct decay profile fitting methods as well as a method adapted from the direct decay profile fitting method for data input from raw files (Scheme S1).…”

Validation and Evaluation of High-Resolution Orbitrap Mass Spectrometry on Molecular Characterization of Dissolved Organic Matter

“…At high m / z values, for example, at m / z 521 Da (Figure d), Orbitrap MS shows good baseline. This is mainly caused by the root-cut process in data acquisition, which limits the potential custom processing on the free induction decay signal, like short-time FT . The problem can be resolved by using third-party data acquisition systems, such as FTMS Booster (Spectroswiss, Switzerland).…”