An EC-CE-C4 D flow system was applied to the investigation of electrocatalytic processes by monitoring carboxylic acids formed during the electro-oxidation at various potentials of primary alcohols (mixture of 1mmol/L of ethanol, n-propanol, n-butanol and n-pentanol) in acidic, neutral and alkaline media. The electro-oxidation was carried out on gold and platinum disk electrodes (3mm of diameter) in a thin-layer electrochemical flow cell. Products were sampled 50μm apart from the electrode directly into the capillary. All the generated carboxylates were determined in near real time (less than 2min) by CE-C4 D in counter-flow mode, with Tris/HCl buffer solution (pH8.6) as BGE. Long sequences of 5-min experiments were run automatically, exploring the applied potential, electrolysis time and solution composition. Electro-oxidation at 1.5V (versus Ag/AgCl quasi-reference) during 50s in acidic medium was found appropriate for both Pt and Au electrodes when the determination of alcohols after derivatization is intended. A noteworthy selectivity effect was observed on the Au electrode. The signal corresponding to pentanoate is similar on both electrodes while the signal of ethanoate (acetate) is four times larger on gold than on platinum. The carboxylate signals were lower in alkaline medium (below the determination limit on Pt) than in acidic and neutral media. On gold, the formation of carboxylates was anticipated (0.85V in alkaline medium versus 1.40V in neutral medium). The automatic online monitoring of electrochemical processes by EC-CE-C4 D holds great potential to investigate ionic/ionizable intermediates/products of new electrocatalysts and/or alternative fuels.