Integrating Electrochemical Electrodes into Mass Spectrometry Ionization Sources for Detection of Transient Intermediates.

Identifying short-lived transient intermediates is challenging due to their brief lifetimes (as short as nanoseconds and even picoseconds) and therefore low concentrations in many chemical processes. Conducting electrochemical reactions within mass spectrometry ion sources (i.e., in-source or in situ EC-MS) offers the advantage of minimizing the distance between the electrodes and the mass spectrometer, thereby improving the detection of transient intermediates. However, a key challenge for in-source EC-MS is the effective integration of the electrodes into the MS ion sources. This mini-review highlights three main integration strategies: exploiting inherent electrochemical properties, incorporating a two- or three-electrode system, and implementing bipolar electrodes, focusing on the underlying mechanisms, experimental setups, and applications of these approaches. Future perspectives emphasize the directions of designing and modifying ionization sources, integrating electrocatalysis, enhancing transfer efficiency, developing automated screening platforms, as well as expanding practical applications.