Final Exam-Elvin Cabrera

About the event

Speaker:  Elvin Cabrera

Group:  Professor Brian Clowers

Title:  COMPRESSING EXPERIMENTAL TIMESCALES IN DRIFT TUBE ION MOBILITY – ION TRAP MASS SPECTROMETRY

Abstract:

Drift tube ion mobility spectrometry (IMS) is a technique that measures the mobility coefficient of ions in the presence of an inert drift gas of known composition. This mobility coefficient is a metric related to the ion-neutral cross section that can be used to make inferences about the structure of an ion. IMS was initially used as a standalone detector for chemical warfare agents, explosives, narcotics, and other simple organic vapors. However, the utility of this technique for structural characterization is bolstered by coupling an IMS with a mass spectrometer (MS), where the mass of the ion can also be determined. Although the data from both techniques is complementary, the synchronous operation of the instrumentation itself typically is not, and the relative duty cycles must first be considered. This is especially true for drift tube IMS and ion trap mass spectrometers, where each respective instrument operates at similar timescales and thus makes nesting the data from one domain in the other difficult. Although methods for coupling IMS with ion traps have been developed, the efficiency of these early methods was low with regards to both ion utilization and experimental time. To this end, the development of frequency-based multiplexing methods such as Fourier transform ion mobility-mass spectrometry (FT-IM-MS) has been a necessary innovation in order to achieve efficient IM-MS experiments. Thus far, through FT-IM-MS, increases in signal-to-noise ratios, resolving power, and ion throughput have been achieved. Additionally, experiments that used to take tens of minutes or hours with early IM-MS methods have been reduced to single minutes by implementation of FT-IM-MS.

Contained within this dissertation are theoretical considerations and optimizations that aim to increase the performance of frequency modulated IM-MS. Early efforts were focused on synchronization of the IMS and MS in order to increase the precision of frequency assignment in generated ion transients. Following this, novel frequency modulation strategies were developed in order to increase the efficiency of FT-IM-MS. Concluding this dissertation is work where a framework was developed for implementing compressed sensing in ion mobility-mass spectrometry (CS-IM-MS) where full signal reconstructions are possible using randomized and under sampled frequency sweeps. Through CS-IM-MS, experimental timescales are reduced to single seconds while also maintaining the high performance of traditional frequency modulated IM-MS experiments.