The flavor and colloidal stability of beer are directly influenced by its content of reducing substances. Dark beers are known for their excellent flavor stability compared with pale beers owing to the high amounts of endogenous antioxidants. Ion chromatography with electrochemical detection using a glassy carbon electrode in reversed-phase high-performance liquid chromatography or a platinum electrode in the ion-exclusion mode were applied for determination of antioxidant additives in beers (sulfite and ascorbic acid). Determination of ascorbic acid on its own was shown to be feasible (using the glassy carbon electrode), whereas determination of sulfite was unsuccessful (using a platinum electrode), whether on its own or together with ascorbic acid. Additionally, the presence of natural antioxidants (e.g., reductones from the Maillard reaction, phenolic compounds) was demonstrated, which allows differentiation between beer types.