Time-frequency analysis of Fourier transform mass spectrometry data by the hilbert transform-based time-domain method

Rich information possesses within the transient image current signal collected from a Fourier transform (FT) mass spectrometer. The central frequency corresponds to the mass to charge ratio of an ion, the amplitude decay profile corresponds to its collision cross sections (CCS). Conventionally, fast Fourier transform (FFT) was applied to transfer the time-domain transient data to frequency-domain. There are demanding needs to develop efficient data processing methods to improve the mass accuracy and resolution of the constructed mass spectrum, while shortening the length of the transient data for high-throughput analysis. In this work, a Hilbert transform based time domain method was developed, so that time-frequency analysis of ion transient data could be performed. This method could accurately extract the instantaneous ion motional frequency and amplitude, which could potentially improve the mass accuracy and mass resolution of a FT-based mass spectrometer. Furthermore, ion CCSs could also be acquired from the ion motion decay profiles.