A step sweep voltammetry (SSV) flow electrochemical (EC) mass spectrometry (MS) platform was developed for real-time and in situ
mapping of EC reaction pathways. By integrating a flow EC cell into the
pneumatic spray nozzle followed by atmospheric chemical ionization,
this setup was capable of in situ MS monitoring of short-lived
EC intermediates with enhanced sensitivity. This setup also realized
precise measurement and control of the electrode potential during in situ
EC-MS analysis, which can provide detailed information on the interplay
of reaction pathways under different electrode potentials. Taking the
EC reductive cross coupling of nitroarenes with arylboronic acids as an
example, SSV-MS had identified 13 compounds among four reaction
pathways. Among these, the electrode potential of active nitrene and
cross coupling intermediates were measured for the first time and the
structure of the nitroso coupling complex was also confirmed by MS. With
the systematic measurement of electrode potential of the intermediates
and products, SSV-MS had clearly mapped out the synergies and
competitions between different reaction pathways, offering key insights
for optimizing reaction conditions and investigating reaction mechanisms
for EC research.（DOI：10.1021/acs.analchem.4c04117）