Over the past decade, the environment has been polluted by a wide spectrum of exogenous chemicals and environmental analysis has become one of the most progressive parts of analytical research. The aim of this work was to determine the kinetics of natural degradation, and to identify the degradation products of the massively used estrogenic drug, 17-α-ethinylestradiol. The photodegradation, oxidation and thermostability conditions were selected according to ICH requirements for pharmaceutical stability testing. A simple 72-h photodegradation study in purified water exhibited significant first-order kinetics with the kinetic constant k = 0.0303 h-1, and degradation halftime 22.8 h. The basic halftime could be reduced to 17.1 h by the addition of sea salt, and increase in temperature. Monohydroxy, dihydroxy and dehydrogenated derivatives of ethinylestradiol with intact steroidal structure were identified as major degradation products resulting from simple photodegradation. The addition of an oxidative agent significantly accelerated the degradation rate; combined with higher temperature, the degradation halftime was reduced to 1.1 h with the first-order kinetic constant k = 0.632 h-1. TOC analysis showed a notable decrease of organic mass (18% in 3 days) during oxidation experiments, and confirmed the degradation of steroidal structure.

• Keywords
• 17-Alpha-ethinylestradiol, Degradation kinetic, Endocrine disruptor, Environmental model, Natural degradation,
• MeSH
• Water Pollutants, Chemical analysis   radiation effects   MeSH
• Ethinyl Estradiol analysis   radiation effects   MeSH
• Photolysis MeSH
• Kinetics MeSH
• Seawater chemistry   MeSH
• Gas Chromatography-Mass Spectrometry MeSH
• Fresh Water chemistry   MeSH
• Light * MeSH
• Models, Theoretical MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Water Pollutants, Chemical MeSH
• Ethinyl Estradiol MeSH