Electro-hydrodynamic study for high efficiency ion transfer for mass spectrometry analysis
Abstract
Mass spectrometry (MS) is considered as a gold standard for chemical analysis. A vision towards clinical/biological mass spectrometry is ongoing, to facilitate development of highly potent devices for biomedical, point of care and/or general purpose in situ analysis. The key developments in this context have been - ambient ionization sources and miniature MS systems. Atmospheric/ambient ionization methods make possible for the interrogation of biological samples particularly in situ. Miniature MS systems allow for simple, efficient, on site analysis. However, their routine combination for the development of high efficiency biological mass spectrometry systems is possible by overcoming certain key technological challenges, particularly the inefficient ion transfer pathway from ion sources (at atmospheric pressure) to mass analyzers (at high vacuum). In this thesis, fundamental electro-hydrodynamic transport studies in MS systems have been made to direct informed development of high efficiency MS systems. Methods and devices have been developed, to collect gas phase ions from ambient/atmospheric pressure ion sources and transfer them over long distances for mass spectrometric analysis. Theoretical studies of ambient ion transport, continuum scale fluid dynamic simulations and experimental tests demonstrate that laminar flow can transfer ions over long distances (over 6 m). The typical angular discrimination effects encountered when sampling ions from ambient ionization sources are minimized, and the sampling of relatively large surface areas is demonstrated. Applications to multiplexed chemical analysis have been demonstrated on samples at locations remote from the mass spectrometer. Ion sampling into relatively small MS inlets and transfer of ions through MS interfaces is studied via multiphysics electro-hydrodynamic simulations. The gas phase ions sampled into MS interfaces need to be delivered to a high vacuum (at ∼10-3 Torr or lower) for mass analysis. In miniature MS systems which use compromised pumping systems to minimize weight and power, this is made possible using a novel interface design v.i.z. discontinuous atmospheric pressure interface (DAPI). The electro-hydrodynamic transport in DAPI is fundamentally different from that in conventional systems and significantly impacts instrument performance. Direct Simulation Monte Carlo methods for gas dynamics and coupled multiphysics models for ion transport have been used to elucidate the dynamics and energetics of DAPI and design high efficiency MS systems for in situ analysis. Based on fundamental understanding gleaned from simulation of DAPI-MS process, simple instrumentation for performing complex ion-molecular chemistry has been designed and evaluated. MS instrumentation development for planetary missions has been explored. The overall study has an impact on instrumentation development of general purpose MS systems.
Degree
Ph.D.
Advisors
Ouyang, Purdue University.
Subject Area
Analytical chemistry|Engineering|Biomedical engineering
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.