High-Capacity Electrostatic Ion Trap with Mass Resolving Power Boosted by High-Order Harmonics

Abstract

A form of electrostatic ion trap mass analyzer, named the orbital frequency analyzer (OFA), has been developed. The ions in the analyzer are trapped around the middle plane and orbit around the central axis perpendicular to the middle plane with high-ellipticity and precessing trajectories. The orbital frequency of the ions in this device has been optimized to be independent of ions’ energy so that the image charge signal picked up by some of the field-forming circular/ring electrodes can be used to produce a mass spectrum after Fourier transform data processing. Spectra acquired by the OFA are rich of high-order harmonics, which offer higher mass resolving power than that for fundamental frequency components. The experiment shows that the resolving power is proportional to the harmonic order and exceeds 150 k for mass-to-charge ratio (m/z) of 526 Th and the transient length of 500 ms. Using high-order harmonics, an isotopic cluster of a heavy protein was resolved with a shorter transient length. The transient signals from different pick-up electrodes give different waveform shapes, and therefore, their harmonic peak distributions in a frequency spectrum are different, thus allowing the removal of unwanted harmonic peaks. The preliminary results also show a wide dynamic range of the analyzer.

Protein Analysis by Electrospray-Orbital Frequency Analyzer with Charge Detection Mass Spectrometry Algorithm

“…More detailed description of the system can be found elsewhere. 14 Standard proteins were used to demonstrate CDMS capability of OFA. Myoglobin from equine heart and aldolase from rabbit muscle were purchased from Sigma-Aldrich.…”

“…Due to precession motion, ions are evenly distributed in this disk-shaped volume inside the trap, resulting in an even lower space charge density than that in the Orbitrap analyzer, where the orbit diameter and the axial oscillation amplitude of ions are only about 20 and 14 mm, respectively. 14,15 By employing high order harmonics analysis, mass resolving power of 155000 was achieved at m/z = 526 Th for a 500 ms transient, and analysis of electrosprayed cytochrome C was demonstrated. 14 In this work, we extend application of the OFA analyzer to CDMS for larger proteins.…”

“…14,15 By employing high order harmonics analysis, mass resolving power of 155000 was achieved at m/z = 526 Th for a 500 ms transient, and analysis of electrosprayed cytochrome C was demonstrated. 14 In this work, we extend application of the OFA analyzer to CDMS for larger proteins. Being different from the other types of electrostatic analysers, the image charge signal picked up in the OFA is a pulsed waveform, and its frequency domain contains many high harmonic components.…”

“…In our lab, a new electrostatic analyzer, the orbital frequency analyzer (OFA) was developed for high-resolution FTMS. , In the OFA, ions are injected from an external curved ion guide in all directions, creating a large disc shaped ion cloud with diameter of about 180 mm. Due to precession motion, ions are evenly distributed in this disk-shaped volume inside the trap, resulting in an even lower space charge density than that in the Orbitrap analyzer, where the orbit diameter and the axial oscillation amplitude of ions are only about 20 and 14 mm, respectively. , By employing high order harmonics analysis, mass resolving power of 155000 was achieved at m / z = 526 Th for a 500 ms transient, and analysis of electrosprayed cytochrome C was demonstrated .…”

“…In our lab, a new electrostatic analyzer, the orbital frequency analyzer (OFA) was developed for high-resolution FTMS. , In the OFA, ions are injected from an external curved ion guide in all directions, creating a large disc shaped ion cloud with diameter of about 180 mm. Due to precession motion, ions are evenly distributed in this disk-shaped volume inside the trap, resulting in an even lower space charge density than that in the Orbitrap analyzer, where the orbit diameter and the axial oscillation amplitude of ions are only about 20 and 14 mm, respectively. , By employing high order harmonics analysis, mass resolving power of 155000 was achieved at m / z = 526 Th for a 500 ms transient, and analysis of electrosprayed cytochrome C was demonstrated . In this work, we extend application of the OFA analyzer to CDMS for larger proteins.…”