Real-time monitoring of the gas phase reactions of a single ion population using the remeasurement experiment in Fourier transform ion cyclotron resonance mass spectrometry

Solvation of acylium fragment ions in electrospray ionization quadrupole ion trap and Fourier transform ion cyclotron resonance mass spectrometry

In electrospray ionization (ESI) quadrupole ion trap and Fourier transform ion cyclotron resonance mass spectrometry, certain fragment ions (e.g. acylium ions) generated either during the ion transportation process (in the source interface region) or in the ion trap are found to undergo ion--molecule reactions with ESI solvent molecules (water, acetonitrile and aliphatic alcohols) to form adduct species. These unexpected solvated fragment ions severely complicate the interpretation of mass spectrometic data. High-resolution accurate mass measurements are important in establishing the elemental compositions of these adduct species and preventing erroneous data interpretation.

Investigation of low-voltage on-resonance ion selection for Fourier transform mass spectrometry

Low-voltage on-resonance ion selection (LOIS) was recently introduced as an alternative technique for ion selection and storage. Under high pressure conditions and similar to the technique of quadrupolar axialization, unwanted (unselected) trapped ions are eliminated from the analysis cell through collisions with cell plates following orbital expansion. The ions remaining after tens of seconds of mass selection can be detected with better coherence, leading to improvements in ion detection and sensitivity. Here, experiments designed to test ion remeasurement and ion transfer capabilities are presented. Simulations of ion motion give insight into the possible mechanism of ion cooling, which does appear to be the same as that of the axialization process. Because of its ease of use, lack of need for additional hardware devices, and comparable ion selection results, LOIS is an attractive alternative for trapped ion experiments.

Two-way conversation with a mass spectrometer: nondestructive interactive mass spectrometry

Most mass spectrometers employ destructive detection, so that it is necessary to repeat an experiment in order to vary even one parameter. In contrast, Fourier transform ion cyclotron resonance mass spectrometry offers nondestructive detection, so that ions remain available for further manipulation and redetection. Here, we show for the first time how to perform mass spectrometry interactively. Following each elementary experimental stage, such as ion generation, isolation, dissociation, or detection, the operator is free to choose and tailor the next stage without creating a fresh supply of ions. For example, we can test the effect of varying one parameter over several values without having to repeat the entire experimental event sequence each time, much like varying one letter or word in a sentence without having to rewrite the whole sentence. Such interactive control promises to speed development of complex experimental event sequences, as for optimizing the sequencing and structural analysis of tiny amounts (e.g., femtomoles or less) of biomacromolecules (peptides, nucleic acids, oligosaccharides).

High-resolution multistage MS, MS2, and MS3 matrix-assisted laser desorption/ionization FT-ICR mass spectra of peptides from a single laser shot

By combined and repeated use of sustained off-resonance irradiation (SORI) for ion dissociation, stored waveform inverse Fourier transform (SWIFT) waveforms for ion isolation, and ion axialization and remeasurements techniques, we obtain for the first time MS, MS2, and MS3 FT-ICR mass spectra from peptide ions (enzymatic digest products of horse cytochrome c) produced from a single laser shot. The successive fragmentation of gas-phase ions detected from the same initial batch of ions increases the sensitivity of analysis of trace amounts of biological samples in structural mass spectrometry, and fragment identification is facilitated by resolution of carbon-13 isotopic distributions. The method is illustrated by analyses of subfemtomole amounts of crudely purified samples of tryptic digest solutions of horse cytochrome c and bovine cytochrome c. The high-resolution primary ion mass spectrum, along with the collision-induced dissociation (CID) and MSn capabilities of FT-ICR, help to determine the primary amino acid sequence of the fragment ions beyond what is obtained from enzymatic digestion alone, without prior chromatographic separation and purification.

Remeasurement at high resolving power in fourier transform ion cyclotron resonance mass spectrometry

The Fourier transform ion cyclotron resonance mass spectrometry remeasurement experiment is demonstrated and evaluated under high resolution conditions. Signal-to-noise enhancement is observed for isotopically resolved bovine insulin peaks at a resolution of ∼ 31,000 (full width at half height). The experiment is sensitive to spacecharge effects and resultant changes in scan-to-scan signal-to-noise and resolution. Coulombic repulsion in the ion cloud during the high resolution remeasurement experiment can cause the cyclotron frequency to shift through the duration of the experiment, which results in broadened peak shapes when individual remeasurement spectra are coadded. By either reducing the number of ions in the cell or allowing the ion cloud to diffuse during the lifetime of the experiment, high resolution remeasurement spectra can be coadded without peak broadening or degradation of signal-to-noise ratio.