| This dissertation presents research in the fundamental aspects of the quadrupole ion trap mass spectrometer. Recent advances have provided extraordinary improvements in its capabilities. Many of these new capabilities have come from a more complete understanding of fundamentals of operation of the quadrupole ion trap.;It had been previously reported that the mass assignments for ions of certain compounds were shifted to a value either higher or lower than their correct mass. The difference between the measured mass and the true mass has been termed a mass shift. Experiments performed using the M$sp+$ ions of the ortho, meta, and para isomers of trifluoromethylbenzonitrile did not find consistent mass shifts. The experiments failed to provide any evidence of the previously reported correlation of apparent mass shifts with the dipole moment of ions. The mass shifts observed were small enough, even at reduced scan speeds, that they could be attributed to factors such as quantization noise in the digital-to-analog Converter (DAC) or instrumental calibration drift. Because the isomeric mass shifts were not consistently observed in these experiments, the existence of such mass shifts was found to be questionable.;Also studied were methods to increase the ion ejection and detection efficiency of the quadrupole ion trap. To maximize the analytical sensitivity of the quadrupole ion trap, it is necessary to efficiently eject all stored ions to the detector. A new scan method, developed previously in our lab, was investigated in detail in this dissertation. This new scan method ejects trapped ions to the detector by removing the RF trapping field while a positive DC pulse is applied to the ring electrode and a differential AC signal is applied across the endcap electrodes. The ion ejection efficiency by RF Removal was typically found to be ten times greater than by the traditional mass selective instability scan method. The increase in ion signal intensity leads to the conclusion that only a small fraction of the ions created and stored in the ion trap are being effectively ejected using mass selective instability scan. |
