MASS SPECTROMETRIC INVESTIGATIONS OF STRUCTURALLY DIAGNOSTIC ION-MOLECULE REACTIONS AND OF MOLECULAR STRUCTURES OF ASPHALTENES

Tandem mass spectrometry (MS/MS) has proven to be a powerful tool for the molecular-level characterization of components of complex mixtures due to its ability to study ionized molecules with high sensitivity, selectivity and specificity. By combining MS/MS with liquid chromatography (LC) to enable front end separation of complex mixtures, trace level analysis of components in these mixtures is possible. Hence, LC-MS/MS has proven invaluable in the separation and characterization of saturated, alkyl aromatic, and polycyclic aromatic hydrocarbon constituents of crude oil. The most common MS/MS method involves collision-activated dissociation of mass-selected ions. Additionally, MS/MS strategies utilizing functional-group or isomer specific ion-molecule reactions have been recognized as a fast and efficient way to identify specific analytes among mixture components. However, the mechanisms of many gas-phase reactions, including dissociation and ion-molecule reactions, are not easily deciphered using MS alone. Thus, density functional theory (DFT) calculations may be used in combination with MS/MS data to derive reaction pathways leading to the formation of intermediate and product ions. Knowledge of the structures of these intermediate and product ions and pathways to their formation may be used to develop new mass spectrometry methodologies for elucidation of structures of unknown components in mixtures and to identify better reagents for functional-group and isomer specific ion-molecule reactions