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APPLICATIONS OF FOURIER TRANSFORM MASS SPECTROMETRY
Abstract
A Fourier Transform mass spectrometer (FT-MS) was built in our laboratory. The capabilities of the instrument were studied and its performance was characterized. The ultra-high resolving power of the instrument was tested and a resolution of 750,000 at mass 78 was obtained. It was demonstrated that increasing resolution in FT-MS is accompanied by improvement in signal-to-noise, and the essential trade-off is resolution vs. mass range rather than resolution vs. signal-to-noise, as in other forms of mass spectrometry. The investigation of low-pressure chemical ionization was carried out using the standard reagent gases at low 10('-6) torr range with a variety of analytes at partial pressures in the 10('-7) - 10('-8) torr range. Conditions for obtaining routine and reproducible chemical ionization spectra were determined. These experiments demonstrated the capabilities of the FT-MS in producing CI spectra with controllable and high rate of proton transfer. Additional experiments were designed to show the other unique features of the technique such as: self-CI (reagent less CI), double-resonance, use of specific reagents for chemical ionization, negative ion CI, deuterium exchange CI, and chemical ionization of samples of biological interest. In FT-MS, exact mass determination rests on the abilities to measure ion resonance frequencies precisely and relate frequency to mass accurately. The mathematical relationship between mass and resonance frequency was investigated and the parameters which affect this relationship were characterized. A typical mass accuracy of 3ppm was obtained using a parabolic mass calibration procedure. A factor of two improvement in mass resolution was gained by elimination of phase distortion which results from practical ion excitation methods, and the broad skirting near the bases of peaks, inherent in magnitude mode display, was attenuated. This was accomplished using a convolution-based phase-correction technique. The applications of this method were studied in both direct and mixer modes of FT-MS operation. Based on these developments, new capabilities such as GC/FT-MS and collisional activation using multiple resonance techniques are forecast.
Subject Area
Analytical chemistry
Recommended Citation
GHADERI, SAHBA, "APPLICATIONS OF FOURIER TRANSFORM MASS SPECTROMETRY" (1981). ETD collection for University of Nebraska-Lincoln. AAI8208353.
https://digitalcommons.unl.edu/dissertations/AAI8208353