title: Transformation of 17β-estradiol in humic acid solution by ε-MnO2 nanorods as probed by high-resolution mass spectrometry combined with (13)C labeling.
abstract: Steroidal estrogens (SEs), widespread in aquatic systems, have a potential to disrupt the endocrine system of wildlife species and humans. In our experiments, the performance of ε-MnO2 nanorods in transforming 17β-estradiol (E2) was investigated, and the effect of humic acid (HA) on the reaction behaviors was systematically characterized. Reconfiguration of humic molecules was also investigated by high-performance size exclusion chromatography (HPSEC). Results indicated that ε-MnO2 nanomaterials ensured efficient removal of E2 from the aqueous solution. The presence of HA hindered the transformation of E2, while enhanced the cross-coupling between E2 and humic molecules. In particular, we used a mixture of un-labeled E2 and (13)C3-labeled E2 at a 1: 1 set ratio (w/w) to probe the reaction products via high-resolution mass spectrometry (HRMS). The combination of HRMS and (13)C3-labeling revealed the intermediate products including estrone (E1), and hydroxylated, quinone-like, and ring-opened species, as well as E2 dimer and trimer. More importantly, possible cross-coupling products between E2 and HA were also identified. A reaction mechanism including two-electron oxidation and single-electron oxidation was proposed. The applied analytical approach using HRMS along with (13)C3-labeling for reaction-product identification is crucial to understanding the role of HA in the transformation of SEs.
authors.affiliation: Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China; Department of Crop and Soil Sciences, University of Georgia, Griffin, GA 30223, USA.
authors.forename: Kai
authors.initials: K
authors.lastname: Sun
authors.affiliation: Department of Crop and Soil Sciences, University of Georgia, Griffin, GA 30223, USA.
authors.forename: Shangtao
authors.initials: S
authors.lastname: Liang
authors.affiliation: Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Fuxing
authors.initials: F
authors.lastname: Kang
authors.affiliation: Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China. Electronic address: gaoyanzheng@njau.edu.cn.
authors.forename: Yanzheng
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Department of Crop and Soil Sciences, University of Georgia, Griffin, GA 30223, USA. Electronic address: qhuang@uga.edu.
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Huang
mesh_terms: D002247:Carbon Isotopes; D004958:Estradiol / Q000737:chemistry*; D004967:Estrogens / Q000737:chemistry*; D004970:Estrone / Q000737:chemistry; D006812:Humic Substances; D007553:Isotope Labeling; D017895:Manganese Compounds / Q000737:chemistry*; D013058:Mass Spectrometry; D043942:Nanotubes / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D012996:Solutions; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D004967:Estrogens; D006812:Humic Substances; D017895:Manganese Compounds; D010087:Oxides; D012996:Solutions; D014874:Water Pollutants, Chemical; D004970:Estrone; D004958:Estradiol; C027424:manganese oxide
keywords: 17β-estradiol; High-resolution mass spectrometry; Humic acid; Product identification; Transformation; ε-MnO(2) nanorods