Applications of electrospray ionization mass spectrometry to organic chemistry

The new technique of electrospray ionization mass spectrometry (ESI-MS) has revolutionized the accurate mass measurement of biopolymers. More and more studies have shown that ESI-MS reflects a great extend of solution chemistry while other ionization methods such as FAB-MS (fast atomic bombardment) and LD-MS (laser desorption) are good for studying gas phase chemistry. The present work is to apply this incredible technique to organic chemistry. The mild ionization process and highly efficient ion formation of ESI-MS make it possible to analyze compounds which are fragile and not volatile such as alkaloids, metal complexes, fullerene derivatives, etc. Under normal conditions, only the molecular ions are detected. More structural information can also be obtained by formation of fragments by the CID (collision induced dissociation) technique. Compounds with groups which can be protonated or attached by metal ions are easily analyzed in the positive ion mode, while compounds with acidic groups may be observed in the negative ion mode. For neutral compounds, derivatization is necessary since preformed ions are normally required for ESI-MS measurement.; Several important and unique features of ESI-MS have been examined. The most significant discoveries are: (1) mixture of compounds can be analyzed without separation since only molecular ions are observed; (2) tagged compounds can be used for monitoring the progress of organic reactions and surveying chemical properties of certain compounds; (3) relative binding strength or reactivity can be estimated; (4) reduction of transition metal ions under high repeller voltage suggests that the potential use of ESI-MS for studying redox chemistry.; ESI-MS has been shown to be good not only for characterization of molecules but also for mechanistic studies. With its high sensitivity, it can also be useful for analysis of drug metabolites. Although ESI-MS has its own limitations in regard to structures of the analytes, the current work shows that its future in organic chemistry is promising.