Improved instrumentation for magnetic field focusing electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.

摘要

The use of mass spectrometry has experienced rapid growth over the last decade. The development of new ionization sources, in particular electrospray ionization (ESI), has made mass spectrometry a candidate for analyzing large biomolecules and synthetic polymers directly from solution. The coupling of an atmospheric pressure source like ESI to a mass spectrometer has proven challenging. Several interfaces have been evaluated to bring the ionization capabilities of ESI and the high resolving power and mass accuracy of FTICR mass spectrometry together. A new approach developed in our laboratory uses concentric pumping stages to position the source inside the magnet bore. Ions are focused into the cell by the magnetic field eliminating the need for an external ion guide. The goal of this work is to evaluate new design features to improve the overall performance of the magnetic field focusing FTICR mass spectrometer.; The work presented here details the design and construction of a new spectrometer built within a 6 Tesla superconducting magnet. Improvements include reducing the length of the pumping chambers by over 40" without eliminating any pumping stages. The mechanical shutter was modified to improve actuation speed, reproducibility and reliability.; The versatility of the system was tested using different source configurations. A probe mounted solid sample heater was used to volatilize solid C{dollar}sb{lcub}60{rcub}{dollar} in the shutter region. Neutral C{dollar}sb{lcub}60{rcub}{dollar} was admitted into the cell through the shutter and ionized by electron impact ionization. A probe mounted ESI source was used to study large multiply charged ions. Infrared multi-photon dissociation (IRMPD) was also available to provide structural information on large biomolecules. Due to limited access to the ESI source inside the probe, an elongated capillary was evaluated to bring the spray source outside of the magnet bore.; To improve control over the mass spectrometer, in particular the generation of new excitation waveforms, a PC based data station was constructed. Its unique capability to continuously output arbitrary waveforms was exploited to perform selective broadband quadrupolar excitation. Axialization experiments were also performed to evaluate the extent of non-ideal fields as ions move away from the center of the cell.