ARS | Publication request: A radioassay-based approach to investigate fate and transformation of conjugated and free estrogens in an agricultural soil

Submitted to: Environmental Engineering Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 3, 2012
Publication Date: February 1, 2013
Repository URL: http://handle.nal.usda.gov/10113/55777
Citation: Shrestha, S.L., Casey, F.X.M., Hakk, H., Padmanabham, G. 2013. A radioassay-based approach to investigate fate and transformation of conjugated and free estrogens in an agricultural soil. Environmental Engineering Science. 30:89-96.

Interpretive Summary: Estrogens are endocrine-disruptors towards aquatic species, but they are usually excreted at high levels as polar metabolites from humans and animals. These polar metabolites are unstable in the environment, and can degrade back to the biologically-active estrogen. To make it easy to track the fate of such metabolite, we describe a simple, easy, and high recovery approach to investigate the fate of a radiolabeled estrogen metabolite, i.e. 17B-estradiol-3-glucuronide (E2-3G), and its metabolites (free estrogens) in a laboratory setting designed to replicate what happens in the environment. This approach obviated the need to perform complicated operations on each sample normally performed. E2-3G and its metabolites were resolved completely so they could be individually studied. The conversion of E2-3G into metabolites, and movement of E2-3G and its metabolites into the water layer, soil, and gas compartments were adequately accounted for in the radiolabeled, laboratory system described. High recoveries were obtained. Although the method gave lower sensitivity than a sophisticated analytical approach like mass spectrometry, it offered a high level of resolution, and advantages to mass spectrometry when studying the fate of unstable estrogen metabolites in dirty, environmental matrices, These advantages included the relatively low-cost and availability of the instrumentation employed, and ease of analyte detection.

Technical Abstract: Estrogens are endocrine-disruptors towards aquatic species, and are excreted at high levels as conjugates from humans and animals. Radioassay-based approaches for environmental fate studies have been frequently conducted for pesticides; however, such techniques have not been exploited for estrogen conjugates. We describe a simple, robust, and high recovery approach to investigate the fate of a prototype estrogen conjugate, i.e. 17B-estradiol-3-glucuronide (E2-3G), and its metabolites (free estrogens) in a batch study without the need for enzymatic cleavage and/or complicating derivatization. E2-3G and its metabolites were baseline resolved in a single run using high performance liquid chromatography (HPLC) and quantified by liquid scintillation counting of the HPLC effluents. Transformation of E2-3G and the disposition of the metabolites 17B-estradiol and estrone into aqueous, sorbed, and gaseous phases were adequately accounted for in the soil-water batch system. High mass balances ranging from 99.0 to 114.1% were obtained. Although the method gave lower sensitivity (parts per billion) than high resolution mass spectrometry (parts per trillion), it offers sufficient resolution and peculiar advantages to mass spectrometry in studying the fate of labile estrogen conjugates in dirty, environmental matrices, including the relatively low-cost and availability of the instrumentation employed, and ease of analyte detection.