Instrumentation development for miniaturization of ion trap mass spectrometers and the study of ion /surface collisions
Abstract
Concepts in instrument development in academia are enunciated and applied to two projects: (i) the miniaturization of an ion trap and (ii) construction of a QogoQ instrument for the study of ion/surface collisions. In the first project, a miniature (5 mm internal radius) cylindrical ion trap (CIT) was developed and systematic studies of geometric effects have been performed to optimize the instrument. Two CITs were arranged in series to construct a serial array which was operated using a single ion source, detector and rf trapping signal. Ions trapped in the first CIT were later transferred to the second by applying ejecting and retarding do pulses to the endcap electrodes of the CITs. The transfer efficiency is dependent on the amplitude of the do potential applied to eject the ions from the first trap, the amplitude of the do potential applied to retain the ions in the second trap, and the period during which the retarding potential is applied. High-throughput mass spectrometers with multiple-channel ionization source, mass analyzer and detector have also been designed. In the second project, a compact tandem mass spectrometer containing two quadrupole mass analyzers (Q, two octapole ion guides (o) and a static quadrupole ion beam-bending lens (q) (QogoQ configuration) has been built for the study of ion/surface collisions. Positive or negative ions are generated by either electron impact (EI) ionization or chemical ionization (CI), selected by mass-to-charge ratio, and then focused onto a surface at an angle of 45°. The secondary ions generated from collisions with the target surface are collected at an emergent angle of 45° and then mass-analyzed. The capabilities of the QogoQ instrument are demonstrated by experiments on surface-induced dissociation (SID), charge permutation, surface analysis via chemical sputtering, and selective surface modification via ion/surface reactions.
Degree
Ph.D.
Advisors
Cooks, Purdue University.
Subject Area
Analytical chemistry
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