Analysis of the false peaks in extended Hadamard transform ion mobility spectrometry

With the introduction of the extended method in Hadamard transform ion mobility spectrometry (HT-IMS), the modulation defects and the false peaks inherently located in conventional HT techniques could be well suppressed. However, a few false peaks are still located in the demultiplexed data of the extended HT-IMS, which is hard to be explained and seriously degrades the performance of the extended HT techniques. In this research, in order to discover the origin of the false peaks in the extended HT-IMS, the measurements of double and multiple ion peaks with IMS have been implemented and the effects of the peak-peak repulsion on the multiplexed data of HT-IMS have been explored. Results show that in multiplexing IMS, the space charge effect existed between two adjacent ion packets would lead to the shifts (deviations) of the ion signal peaks. Simulation results prove that this tiny shifting in the multiplexed data is another critical reason for the false peaks in the demultiplexed data of extend HT-IMS. This is of positive significance for revealing those unknown false peaks in extended HT-IMS and other similar techniques.