The charge transfer processes for tetracycline and tetracycline derivatives are characterized across the H2O vertical bar 1,2-dicloroethane interface. Stability of tetracycline and tetracycline derivatives, TC, OTC, and CITC is studied in strong acid and alkaline solutions. The analysis of the degraded solutions is carried out with cyclic voltammetry applied to the H2O vertical bar 1,2-dicloroethane interface and the results obtained are complemented with measures of UV-vis spectroscopy in the homogeneous phase. (c) 2005 Elsevier B.V. All rights reserved.