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dc.contributor.authorSchug, Kevin Alberten_US
dc.date.accessioned2014-03-14T20:19:39Z
dc.date.available2014-03-14T20:19:39Z
dc.date.issued2002-10-02en_US
dc.identifier.otheretd-12032002-112120en_US
dc.identifier.urihttp://hdl.handle.net/10919/29886
dc.description.abstractPseudo-molecular ion formation is an artifact common to most analyses performed by electrospray ionization mass spectrometry. These species are non-covalent complexes formed between an analyte of interest and any other components (such as mobile phase, additives, and impurities) present in the ionized sample band. Published literature addresses pseudo-molecular ion formation in routine analyses as well as in complicated molecular recognition processes. The majority of these works are directed towards the formation of complexes in the positive ionization mode. Consequently, investigation of pseudo-molecular ion formation in the negative ionization mode is a logical extension of work in this area. Experiments presented here detail the work performed on elucidation of factors controlling ionization efficiency of aromatic acid pseudo-molecular ions by electrospray ionization in the negative ionization mode. Sets of tested acidic analytes, including ibuprofen derivatives and benzoic acid derivatives, were analyzed in the presence of various solution systems by flow injection analysis to determine the effect of pH, concentration, injection volume, and instrumental parameters on dominant ion forms observed in the mass spectra. These ion forms correspond to a deprotonated molecular ion ([M-H]-), a hydrogen-bound dimer ion ([2M-H]-), and a sodium-bridged dimer ion ([2M-2H+Na]-). Report of the latter ion form is unique to this work. Response of these ion forms were found to vary greatly with changing solution parameters, particularly in the presence of common LC-MS modifiers, such as triethylamine, acetic acid, formic acid, and ammonium formate. Results point to the formation of the sodium-bridged dimer ion during gas-phase processes following the release of ions from disintegrated droplets. Ab initio theoretical calculations and correlations with calculated solution phenomena (such as pKa and log P) were used to elucidate structural arrangements and dominant factors controlling pseudo-molecular ion formation by aromatic acids in the negative ionization mode.en_US
dc.publisherVirginia Techen_US
dc.relation.haspartdiss.pdfen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectaciden_US
dc.subjectmass spectrometryen_US
dc.subjectelectrospray ionizationen_US
dc.subjectpseudo-molecular ionen_US
dc.subjectadducten_US
dc.titlePseudo-Molecular Ion Formation by Aromatic Acids in Negative Ionization Mode Electrospray Ionization Mass Spectrometryen_US
dc.typeDissertationen_US
dc.contributor.departmentChemistryen_US
dc.description.degreePh. D.en_US
thesis.degree.namePh. D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineChemistryen_US
dc.contributor.committeechairMcNair, Harold M.en_US
dc.contributor.committeememberAnderson, Mark R.en_US
dc.contributor.committeememberDucker, William A.en_US
dc.contributor.committeememberTaylor, Larry T.en_US
dc.contributor.committeememberViers, Jimmy W.en_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-12032002-112120/en_US
dc.date.sdate2002-12-03en_US
dc.date.rdate2003-12-09
dc.date.adate2002-12-09en_US


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