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Laser desorption - laser photoionization ion trap mass spectrometry for the direct analysis of solid samples Specht, August Anders

Abstract

This thesis describes work associated with the creation of a novel analytical instrument, a two-laser ion trap mass spectrometer. This device combines one of the most sensitive and selective direct solid sampling techniques, two-laser solid sampling, with a very versatile mass spectrometer, the ion trap. This work demonstrates some of the potential advantages associated with coupling these two techniques. The results from this work can be divided into three sections. Section one shows data associated with the development and characterization of this new instrument which couples IR laser desorption followed by UV laser photoionization and analysis using an ion trap mass spectrometer. For calibration, a new type of solid sample preparation method involving activated charcoal as the solid substrate was used. It was found that both the IR and UV intensity, and the delay between them, play an important role in both the magnitude and type of signals observed. A method of gas phase ion accumulation was also examined. Finally , this section demonstrates the technique's ability to provide direct qualitative information for PAH content for N.I.S.T. SRM 1944 river sediment with no sample pre-treatment. The second section of this thesis shows data relating to the detection of the pharmaceutical agent Spiperone directly on a solid biologically relevant tissue matrix. This data shows that the two-laser ion trap method is suitable for applications with complicated matrices with no need for sample pre-treatment. Finally, the third section of this thesis describes the addition of a third, tunable laser to the system. This laser allows for optical probing of the trapped ion cloud. Visible absorption spectra for the gas phase PAH cations isomers phenanthrene and anthracene are shown. The third laser also allows for the possibility of wavelength selective photodissociation of PAH isomers for resolving complicated isomer mixtures.

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