Generalization of an Open Dynamically Harmonized Cell for Ultrahigh FT ICR Resolution

Abstract

FT ICR mass spectrometry is the leader in resolving power among all mass spectrometry methods. Introduction of the dynamically harmonized measuring cella closed-cylindrical cell with specifically shaped electrodeshelps to reach the resolving power of more than 107 with a magnetic field of about 7 T. From the theory of FT ICR mass spectrometry it follows that the resolving power of this type of instrument depends linearly on the magnetic field under various conditions. However, the results obtained on this type of mass spectrometer with the maximum magnetic field achievable today did not show a proportional increase in resolving power. In one of our previous papers, we assumed that the reason for this was insufficient vacuum inside the cell, since vacuum quality should be at least proportional to the magnetic field, since the mean free run time decreases proportionally to the magnetic field growth. We have presented an open modification of the dynamically harmonized cell that can help improve the cell pumping conditions. However, the electric potential distribution inside this new cell is slightly different from the ideal (harmonic) one, obtained inside the closed version of the cell, and the resolving power may have been limited by this difference.

The analytical solution for the optimum voltage on regularizing electrodes of the open dynamically harmonized cell

“…In this article, we continue the analytical study of the field distribution in an open DHC (described in the previous papers 1,2 ). A method for voltage optimization of the regularizing electrodes has been developed.…”

“…The outcome of the numerical optimization of the comet formation time throughout the whole area of ion rotation (provided in Lioznov and Nikolaev 2 ) can be compared with those reported in the equation (21). The time of comet formation in the region of ion rotation was maximized in that paper through numerical optimization using the derived E false( ρ false) / ρ integral (where E is the electric field strength).…”

“…In a recent publication, 2 we have found an analytical solution for the electric potential inside such a cell and have analyzed it numerically in order to obtain a potential as close to the ideal hyperbolic one as possible.…”

“…In recent articles, we have introduced 1 and generalized 2 the open dynamically harmonized cell (DHC). The configuration of the electrodes in an open cell is shown in Figure (1).…”

Large Individual Ion FTICR Measurements from the Mid-1990s Using Reactions for Charge Determination Mass Spectrometry

“…This involves cases where FTICR MS resolving powers significantly exceed those using Orbitraps; particularly for measurements at somewhat lower m / z , with the m / z value that will provide equivalent performance for the two platforms dependent on factors that primarily include the FTICR magnetic field strength, cell design and dimensions. Newer FTICR cell designs, such as the dynamically harmonized cell proposed by Nikolaev and co-workers, provide a basis for improved resolution and pushing the “turnover” in performance to higher m / z . A practical advantage of FTICR can be, depending on design details, the ability to achieve higher vacuum and better pumping speed at the FTICR cell vs an Orbitrap MS due to a more open and efficiently pumped volume.…”