Method and Applications of Ion Collision Cross Section Measurement Based on Fourier Transform-Ion Cyclotron Resonance

The measurement of gas phase collision cross section (CCS) of ions can provide complementary structure information to those typically obtained from mass spectrometry or tandem mass spectrometry. Thus, the ion mobility spectrometry is typically coupled with a mass spectrometer to achieve the advantage after the combination. Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) is characterized by its ultra high resolution and tandem mass spectrometry capabilities. Due to the collisions with neutral molecules, the image current caused by the cyclotron motion of ions in the analysis cell gradually decays under high vacuum condition. Based on this feature, the CCS of ions can be calculated by selecting an appropriate theoretical model and combining with the corresponding algorithm. This method can be directly applied to obtain the value of CCS of the selected ion through the analysis of high-resolution mass spectrometry data without increasing the cost of instrument hardware. With the development and promotion of FT-ICR MS instruments in recent years, such methods have developed rapidly in the past decade and have attracted extensive attention. There are three different ionneutral collision models (Langevin collision model, hardsphere collision model and energetic hardsphere model) which have been applied to connect ion CCS and image current of FT-ICR MS instruments. Time-domain analysis, frequency-domain analysis and time-frequency analysis are three types of data analysis method used to measure ion CCS based on FT-ICR MS. Although the reliability and accuracy of the CCS data provided by such methods need to be further improved, it has been demonstrated its unique advantages in the dynamic CCS measurement and potentials in isomerization study. Such methods can be further combined with ion mobility technology to provide multidimensional ion structure information with the help of FT-ICR′s superior mass resolution and superior ion manipulation capabilities.