Initial photocatalytic degradation intermediates/pathways of 17α-ethynylestradiol: Effect of pH and methanol

This study investigated the photocatalytic degradation of the synthetic oral contraceptive 17α-ethynylestradiol (EE2). Particular attention was paid on the effects of pH and the co-solvent methanol on the degradation intermediates of EE2. Twelve intermediates were identified, and several intermediates reported herein have not been found in previous studies. The degradation efficiency of EE2 and the number of identified intermediates decreased evidently at pH 3 and in the presence of methanol at pH 7. Three photocatalytic degradation pathways were proposed: The transformation of the phenolic moiety (pathway I) is the primary initial reaction pathway; the initial photocatalytic degradation in the aliphatic carbon linked to the aromatic ring (pathway II) only took place at pH 7; the isomerization of EE2 (pathway III) could occur only in the presence of methanol at pH 7. Results from this study underscore the importance of photocatalytic degradation on the removal of estrogenic activity mainly expressed by the phenol moiety of EE2.