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Please use this identifier to cite or link to this item: http://hdl.handle.net/1860/1765

Title: Exploration of the fundamentals of matrix assisted laser desorption/ionization time-of- flight mass spectrometry
Authors: Erb, William Joseph
Keywords: Chemistry;Matrix-assisted laser desorption-ionization;Mass spectrometry
Issue Date: 4-Sep-2007
Abstract: This thesis focuses on the study of different tools used for preparing samples for MALDI TOFMS and the utilization of these tools to study different ionization processes operating in the MALDI experiment. The electrospray deposition technique was employed to study the effect of salt/analyte (S/A) ratio, a critical factor for the quantitation of synthetic polymer samples. The analysis was performed with four different matrices: DHB, CHCA, dithranol, and DCTB, with three different alkali ions: lithium, sodium, and potassium. The results obtained from titrating a PMMA 6800 sample with different alkalis in the presence of different matrices produced varying results, from an “ideal” titration curve using sodium with the DHB matrix to a “non-ideal” titration curve (i.e., increasing analyte signal up to a S/A value of approximately 1, followed by a decreasing analyte signal with further increases in salt) for sodium with the dithranol matrix. Utilization of a specially designed split probe in which the segregation of the PEG 1500 analyte and the lithium hyrdroxide cationization agent was complete, demonstrated the unequivocal proof of gas phase cationization. A dual electrospray deposition system was successfully developed in which two solutions are sprayed simultaneously, ensuring that the contents of the independently prepared samples are not mixed in the solution state. This device was used for the further study of both the gas phase cationization reactions of polymers and the counterion exchange reaction observed with inorganic complexes. Four matrices were used to analyze a ruthenium dimer complex in which the use of all matrices except DCTB led to dissociation of the non-covalent bonds of the dimer complexes. An analysis of hetero ligand ruthenium complexes with all matrices except DCTB demonstrated a counterion exchange reaction where the ClO4- or PF6- counterions were substituted by a matrix anion. Performing TOFMS instrument mass calibration using synthetic polymer calibrants with different molecular weight ranges uncovered visual and mathematical methods for evaluating the accuracy of the calibration function. Statistical analysis of systematic errors in the observed mass deviations enabled development of a correction method that yielded corrected mass values acceptable for use in accurate mass measurements.
URI: http://hdl.handle.net/1860/1765
Appears in Collections:Drexel Theses and Dissertations

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