Nanospray Ionization Efficiency and Infrared Multi-Photon Dissociation In Mass Spectrometry

This dissertation covers research into the ionization efficiency of nanospray, a widely used technique for transferring ions from solution into the gas phase, the modifications required to perform infrared multiphoton dissociation (IRMPD) on a hybrid tandem quadrupole time-of-flight (Qq-TOF) mass spectrometer and practical applications of IRMPD. Infrared-induced dissociations have so far only been performed on Fourier-transform ion cyclotron resonance (FTICR) machines and three-dimensional quadrupole ion traps (QIT). Such machines are limited by the rate of mass scanning (FTICR) or hindrance of multiphoton dissociation by the high operating pressure (QIT).;In order to perform IRMPD on a Qq-TOF mass spectrometer, an infrared laser beam had to be introduced into the quadrupole ion trap. In addition, the trapping conditions had to be modified in order to minimize cooling collisions of the heated ions with gas molecules in the relatively high-pressure collision cell. The infrared beam was introduced coaxial to the ion beam by mounting an IR-transparent window at the detector end of the mass spectrometer. Delivery of the laser beam was accomplished using laser optics components and mirrors. The optimal setup required the use of a water-cooled laser together with a light and flexible hollow wave guide for laser delivery. In order to achieve high sensitivity and resolution conditions on a Qq-TOF mass spectrometer, ions were trapped, collisionally cooled and focused before the time-of-flight analysis. The trapping cell's original pressure conditions did not suit IRMPD requirements and various hardware modifications were examined in order to optimize both IRMPD and ion trapping efficiencies.;The IRMPD technique was found to provide better dissociation control without mass discrimination compared to collision induced dissociation (CID); these conclusions were derived from experiments with a series of analytes including reserpine, apomyoglobin, alcohol dehydrogenase, GroEl and avidin. In addition, IRMPD was applied to non-covalent complexes to remove solvent and buffer adducts in a controlled manner, which was found to facilitate the determination of accurate molecular masses of these complexes. Investigations were also conducted to fragment by means of IRMPD large non-covalent complexes that may be difficult to fragment with the conventional CID technique.;Using a setup consisting of a filled nanospray needle, a video camera and a metal grid as a ruler, the flow rate resulting from electrospraying of the needle content was determined. Using a simple model, the flow rate together with the measured current was used to obtain analyte ionization efficiencies. Experimental results indicate efficiencies varying between 0.1 and 12%.