Electrochemical processes in electrospray ionization mass spectrometry

Abstract

Editorial Comment Last month we presented, as a Special Feature, a set of five articles that constituted a Commentary on the fundamentals and mechanism of electrospray ionization (ESI). These articles produced some lively discussion among the authors on the role of electrochemistry in ESI. Six authors participated in a detailed exchange of views on this topic, the final results of which constitute this month's Special Feature. We particularly hope that younger scientists will find value in this month's Special Feature, not only for the science that it teaches but also what it reveals about the processes by which scientific conclusions are drawn. To a degree, the contributions part the curtains on these processes and show science in action. We sincerely thank the contributors to this discussion. The give and take of intellectual debate is not always easy, and to a remarkable extent this set of authors has maintained good humor and friendships, even when disagreeing strongly on substance. Graham Cooks and Richard Caprioli Copyright 2000 John Wiley & Sons, Ltd.

A Mechanism for Ionization of Nonvolatile Compounds in Mass Spectrometry: Considerations from MALDI and Inlet Ionization

“…Improved desolvation of the charged clusters or producing more small charged clusters would provide a way to enhance sensitivity. Providing the enthalpy necessary for desolvation through a thermal process in vacuum is problematic [91]. However, innovative means of desolvation, such as collisions with surfaces or use of rf fields under low pressure conditions is expected to provide enhanced desolvation and thus sensitivity.…”

A new cluster-ion-beam source for secondary ion mass spectrometry (SIMS) using the electrospray of a pure ionic liquid under high vacuum

“…Since an ionic liquid has large electrochemical window [21], the oxidation of iron, Fe ? Fe 2+ + 2e À , may occur [30,31], eventually affecting the decomposition of the ionic liquid. For a more detailed understanding of the mechanism of the electrochemical decomposition, further study will be required.…”

“…The emitted charged droplets are delivered toward the counter electrode. Note that, in an electrospray process, electrochemical reactions such as oxidation and reduction occur at metal-liquid interfaces [29][30][31]. Consequently, electrospraying can cause electrochemical decomposition of the ionic liquid.…”

A new strategy for ionization enhancement by derivatization for mass spectrometry

“…Mora et al noted that the typical ESI source is a two-electrode system that consists of a capillary with a high applied voltage and an atmospheric sampling aperture plate. They proposed that an electrolytic process must be present in the ESI source for successful ionization according to the law of charge conservation [84]. Consequently, a series of derivatization methods to enhance the sensitivity of ESI-MS based on electron transfer reactions were developed by Van Berkel's group [85,86].…”