Investigation of collision-induced mass spectrometric fragmentation pathways of gaseous ions derived from some compounds of biological and pharmaceutical significance.

摘要

The research reported in this dissertation focuses on a combination of mass spectrometric techniques and gas-phase ion chemistry that were used to interpret the dissociation processes of gaseous ions. Electrospray ionization was used to generate ions while tandem mass spectrometry was used to select the ions and elucidate the chemical structures by monitoring changes in the mass-to-charge ratio. Additional techniques were applied, including isotopic labeling of the investigated compounds, accurate mass measurements and ion-molecule reactions of the precursor and product ions.;Benzylamine and other related amines which serve as important biological and pharmaceutical agents, readily ionize to the protonated form under electrospray ionization. A diagnostic marker for such amines is an intriguing rearrangement of the structure to eliminate a molecule of ammonia or primary amine. We have determined that this elimination occurs through a specific ion-neutral complex pathway which can be widely applied to other protonated compounds such as sulfonamides.;The gas phase chemistry of negative ions is less well understood since most ESI applications have traditionally been applied in positive mode. We have established fragmentation rules based on the formation of ion-neutral complex intermediates for mono-hydroxy carboxylate anions. These fragmentation rules can be applied to determine the site of the OH function within the chemical structure. We have also generated from electrospray five different isomeric product ions at m/z 59 which bare the same empirical formula (C2H3O2-). These findings advance the notion that gas phase anions yield product ions which are less prone to structural rearrangement and therefore may contain more structural information about the parent ion than positively charged product ions.;A comprehensive collision-induced dissociation study of the anions of glucosinolates, a biologically important group of compounds, was performed. A very unusual and high intensity product ion at m/z 75 was determined to be present in the CID spectra of all glucosinolate anions. Based on our understanding of mono-hydroxy carboxylate anion fragmentation, we were able to determine that the dissociation process for m/z 75 occurs through an ion-neutral complex. We utilized the ion at m/z 75 to improve upon current LC-MS/MS methods for better quantitative analysis of glucosinolates.