Abstract: Serial electrochemical flow cells coupled in-line with electrospray ionization mass spectrometry (MS) provides rapid electrochemical (EC) study of biologically relevant oxidation-reduction (redox) reactions. Compounds, introduced by flow injection, are subjected to rapid electrolysis and products were monitored by MS. Serial coulometric EC-MS allows high-throughput study of relative compound reactivity, resultant formation of “related substances” and determaination of metabolic and chemical “soft spots.” Serial coulometric EC-MS thus represents a mechanistic probe that can be consistently and reproducibly applied to large compound libraries to generate “modeling friendly” data for prediction and assessment of drug-like properties.