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

Miao Hu; Linzhou Zhang; Shan He; Chunming Xu; Quan Shi

doi:10.1002/rcm.8096

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

Rapid Commun Mass Spectrom. 2018 May 15;32(9):751-761. doi: 10.1002/rcm.8096.

Authors

Miao Hu^{1

2}, Linzhou Zhang¹, Shan He¹, Chunming Xu¹, Quan Shi¹

Affiliations

¹ State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing, 102249, China.
² CNOOC Research Institute of Refining and Petrochemicals, Beijing, 102200, China.

PMID: 29486526
DOI: 10.1002/rcm.8096

Abstract

Rationale: The collision cross section (CCS) is an important shape parameter which is often used in molecular structure investigation. In Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), the CCS affects the ion signal damping shape due to the effect of ion-neutral collisions. It is potential to obtain ion CCS values from FTICR-MS with the help of a proper ion-collision model.

Methods: We have developed a rapid method to obtain the ion damping profile and CCS for mixtures by only one FTICR-MS measurement. The method utilizes short-time Fourier transform (STFT) to process FTICR-MS time domain signals. The STFT-processed result is a three-dimensional (3D) spectrum which has an additional time axis in addition to the conventional mass-to-charge ratio and intensity domains. The damping profile of each ion can be recognized from the 3D spectrum.

Results: After extracting the decay profile of a specified ion, all the three ion-neutral collision models were tested in curve fitting. The hard-sphere model was proven to be suitable for our experimental setup. A linear relationship was observed between the CCS value and hard-sphere model parameters. Therefore, the CCS values of all the peaks were obtained through the addition of internal model compounds and linear calibration.

Conclusions: 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.