A novel fourier transform ion cyclotron resonance mass spectrometer with improved ion trapping and detection capabilities

Abstract

A novel Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer has been developed for improved biomolecule analysis. A flared metal capillary and an electrodynamic ion funnel were installed in the source region of the instrument for improved ion transmission. The transfer quadrupole is divided into 19 segments, with the capacity for independent control of DC voltage biases for each segment. Restrained ion population transfer (RIPT) is used to transfer ions from the ion accumulation region to the ICR cell. The RIPT ion guide reduces mass discrimination that occurs as a result of time-of-flight effects associated with gated trapping. Increasing the number of applied DC bias voltages from 8 to 18 increases the number of ions that are effectively trapped in the ICR cell. The RIPT ion guide with a novel voltage profile applied during ion transfer provides a 3-to 4-fold increase in the number of ions that are trapped in the ICR cell compared with gated trapping for the same ion accumulation time period. A novel ICR cell was incorporated in the instrument to reduce radial electric field variation for ions with different z-axis oscillation amplitudes. With the ICR cell, called trapping ring electrode cell (TREC), we can tailor the shape of the trapping electric fields to reduce dephasing of coherent cyclotron motion of an excited ion packet. With TREC, nearly an order of magnitude increase in sensitivity is observed. The performance of the instrument with the combination of RIPT, TREC, flared inlet, and ion funnel is presented. (J Am Soc Mass Spectrom 2009, 20, 755-762)

A Novel 9.4 Tesla FTICR Mass Spectrometer with Improved Sensitivity, Mass Resolution, and Mass Range

“…However, many other instrument parameters besides higher magnetic field strength can be modified to improve instrument performance [20], e.g., increased ion transfer and trapping efficiency, and new ICR cell geometries that more closely approach harmonicity in the electrostatic trapping potential at large cyclotron radius [21][22][23]. Increased ion cyclotron radius can reduce space charge frequency shifts [24], and precise control of the number of trapped ions can reduce variation in space charge frequency shifts from successive ion injections [25].…”

Ion behavior in an electrically compensated ion cyclotron resonance trap

“…New electrically compensated trap designs hold significant promise to improve the performance of FTICR MS [1-24] by reducing the deleterious effects of the nonlinearities in the electrical field. We reviewed in detail most of the research on trap compensation in a book chapter [25], and we won’t repeat this perspective here.…”

Improved ion optics for introduction of ions into a 9.4-T Fourier transform ion cyclotron resonance mass spectrometer

“…To accompany this enhancement, the following octopole ion guide after the skimmer has been replaced by a quadrupole. In an octopole ion guide, the pseudopotential varies as r 4 , whereas a quadrupolar pseudopotential varies as r 2 , in which r is the radial position . Therefore, an octopole ion guide can potentially accommodate more ions than a quadrupole because of the radially flatter octopole pseudopotential: e.g.…”