Photodegradation of Scopoletin in Organic Solvents and Aqueous Solutions: Kinetics and Degradation Pathways

Scopoletin (hereafter SCO), an excellent candidate of acaricides, was discovered and developed in China. Photolysis kinetics of SCO in organic solvents and different aqueous media were investigated under 500W Xe lamp. Effects of five surfactants, nitrate (NO3−), nitrite (NO2−), and H2O2 on SCO photolysis and photodegradation pathways of SCO in aqueous were also studied. The results indicated that photolysis rate of SCO in organic solvents was in the sequence of acetone > ethyl acetate > methanol, and the corresponding half-lives were 9.63, 36.47, and 49.50 h, respectively. Photolysis rate of SCO in different aqueous media was in the sequence of pure water > river water > natural seawater, and the half-lives were 5.68, 6.66, and 7.79 h, respectively. The five kinds of surfactants, NO3−, and NO2− had significant photoquenching effects on photolysis of SCO, and H2O2 had photosensitization effects on photolysis of SCO. By separation and identification of photoproducts using LC/ESI-MS, it could be concluded that SCO was photolyzed through photorearrangement, photohydrolysis, and photooxidation of the molecule itself.