Hydrophobic eutectic solvents for endocrine disruptors purification from water: Natural and synthetic estrogens study

Abstract

Effective elimination of natural and artificially synthesized estrogens from water sources and wastewater is very important because even minimal amounts of these substances, considered as endocrine disruptors, are dangerous to humans and wildlife. For the extraction of five estrogens namely estrone, 17α-estradiol, 17β-estradiol, 17α-ethynylestradiol and estriol, hydrophobic eutectic solvents (ES) are newly tested as a green alternative to conventional organic solvents. For this purpose, a series of ES based on a combination of menthol with natural organic acids (octanoic, decanoic and dodecanoic) was prepared in the laboratory. The extraction of estrogens was studied in terms of ES composition, molar ratio of hydrogen bond acceptor and donor, extraction time, extraction rate and reuse. Estrogens were eliminated from the waters at low levels of 10 and 20 μg/mL and their concentrations were monitored using a sensitive HPLC-MS/MS technique. The ES of menthol and octanoic acid in a 1:1 ratio showed the highest extraction efficiency for all estrogens studied, reaching values up to 99.9 % for artificially prepared samples and 97.9 % for real natural and waste waters. Comparable results can be achieved with conventional solvents such as tert-butyl methyl ether, but not with hexane and chloroform. Nevertheless, ES solvents are environmentally sustainable, non-toxic and biodegradable and therefore suitable for industrial wastewater treatment processes.