Department of Chemistry, Purdue University
Chemical reactions in Mass Spectrometry
Mass spectrometry has always depended on chemical reactions including the gas phase bimolecular reactions of chemical ionization and the unimolecular dissociations associated with collisional activation. However, bimolecular solution phase reactions are a recent component of the subject, made possible by the introduction of electrospray ionization and more recently the ambient ionization methods, especially desorption electrospray ionization (DESI).
This presentation covers a variety of homogeneous and heterogeneous phase chemical reactions that are associated with mass spectrometry. The reactions are chosen to illustrate the degree to which MS is a chemical methodology as much as it is a form of spectroscopy. Included are (i) in situ derivatization reactions that accompany the ambient ionization methods and increase ionization efficiency (ii) the use of desorption electrospray ionization (DESI) to sample reacting mixtures (iii) the accelerated reactions that occur in microdroplets in DESI (iv) the heterogeneous reactions that occur when mass selected ions are scattered from or are deposited on a surface (soft landed) (v) the ambient reactions that occur when analytes in solution are heated in coiled tubes and the products sampled using mass spectrometry (atmospheric pressure thermal desorption) and (vi) the heterogeneous reactions that occur in chemical sputtering and the redox reactions that occur at organometallic interfaces prepared by ion soft landing.
In each instance the fundamental phenomenon and potential applications of the methodology will be discussed. Among the reactions is a surface assisted Birch reduction, Fischer indole synthesis, and Borsche-Drechsel cyclization and the Eberlin transacylation.