Ascorbic Acid Electrooxidation: See the Unseen With Real‐Time Electrochemistry–Mass Spectrometry

This work unveils a streamlined yet powerful hyphenated analytical strategy for real‐time detection of electrogenerated oxidation products of one of the most‐studied vitamins, ascorbic acid (AA), directly on the surface of a screen‐printed carbon electrode (SPCE), offering unprecedented mechanistic insight into the AA redox pathway. Unexpectedly, this study revealed the detection of an oxidation product at applied potentials exceeding 1.4 V. To track, detect, and identify AA alongside its electrooxidation products, we deployed advanced online electrochemistry‍–mass spectrometry (EC–MS) as well as electrochemistry–capillary electrophoresis–mass spectrometry (EC–CE–MS). While many mechanistic studies have long established dehydroascorbic acid (DHAA) as the primary product of AA electrooxidation, the present work uncovers an extended electrochemical pathway for rather high electrode potentials. Specifically, when the applied oxidation potential exceeds 1.4 V on the SPCE surface, a secondary, low‐stability oxidation product, 2,3‐oxalyl‐L‐threonolactone (OxTL), is detected. In this potential region, conventional voltammetric techniques are practically unable to detect electrogenerated species because the current response is already dominated by anodic water decomposition. In this report, we demonstrate that short‐lived oxidation products of DHAA can be generated electrochemically and detected in situ by hyphenated EC–MS and EC–CE–MS techniques at relatively positive potentials.