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How to Increase Further the Resolving Power of the Ultrahigh Magnetic Field FT ICR Instruments? The New Concept of the FT ICR Cell–the Open Dynamically Harmonized Cell as a Part of the Vacuum System Wall
journal contributionposted on 2020-12-23, 00:14 authored by Evgeny Nikolaev, Anton Lioznov
FT ICR mass spectrometry continues to be the leader in the resolving power among all mass spectrometry methods. With the introduction of the dynamically harmonized FT ICR cell, it has become possible to achieve the resolving power of more than 10 million at m/q = 1000 with moderate magnetic fields of about 7 T. A further increase in the mass resolving power is desirable mainly for two reasons: with this we are increasing the number of resolved components in analyses of complex mixtures (like oil and natural organic matter (NOM)) and increasing the number of the mass of molecules for which a fine structure can be resolved. In recent years, some attempts have been made to further increase the mass resolving power by increasing the magnetic field and using the multielectrode detection method. An increase in the magnetic field to 21 T did not show a proportional increase in the mass resolving power. Likely, the reason for this is an insufficiently high vacuum to satisfy the requirement of an increase in the mean free path of ions with the increasing magnetic field power. We offer a new design for the FT ICR cell and the whole mass spectrometer, in which an open, dynamically harmonized FT ICR cell is integrated into a vacuum system with the outer surfaces of the cell electrodes at atmospheric pressure. In this design, the trap electrodes are the walls of the vacuum system and have the minimized active surfaces by combining the vacuum system surface and the cell surface into one. In this design, the pumping process is accelerated, and the factor of insufficient vacuum in FT ICR mass spectrometers with an ultrahigh magnetic field is eliminated.