Development of mass spectrometric methods for catalytic studies
Abstract
Instrumental and experimental mass spectrometric methods have been developed which are applicable to catalyst preparation and characterization. The analytical performance of a multiplexed four channel mass spectrometer has been characterized. Four samples can be analyzed simultaneously, in both MS and MSn modes. This instrument could be used to monitor gas-phase products within a catalytic chamber. A new ionization method, atmospheric pressure thermal desorption ionization (APTDI), has been applied to inorganic compounds. The mass spectra of salen-containing complexes are very simple, containing protonated monomers, dimers and trimers. When solid phase mixtures are analyzed via APTDI, protonated mixed-metal clusters are generated, which demonstrate interesting fragmentation to form radical monomers upon collision-induced dissociation, an unseen phenomenon with the "pure" clusters. This ionization method may be useful for generating small metal-containing clusters for catalyst surface preparation via soft landing. Lastly, a new soft landing instrument has been constructed and characterized. An ion funnel provides high current, while a bent ion guide discriminates between ions and neutrals. Both the square quadrupole and an elongated RIT can be operated in a novel RF/DC mode to provide maximum throughput to the landing surface. Currents up to 1 nA have been collected at the landing surface. Peptides, dyes and inorganic complexes have been landed on gold surfaces and self-assembled monolayers. Subsequent nanosprayed rinses have demonstrated an overall efficiency of ∼0.2-0.4% from solution to surface. Additional analyses of landed surfaces via desorption electrospray ionization and x-ray photoelectron spectroscopy have demonstrated successful landing. This instrument is intended for preparation of catalytic surfaces via soft landing.
Degree
M.S.
Advisors
Cooks, Purdue University.
Subject Area
Analytical chemistry
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