Stereoselective Sorption of Trenbolone and Estradiol Isomers

Regulatory decisions regarding the land application of manure and the use of growth-promoting hormone implants in beef require quantitative information on the environmental behavior of steroid hormones. Hormone implants typically include the 17β-isomer form of the synthetic androgen trenbolone and the natural estrogen estradiol. Most laboratory studies conducted to date focus on the fate of the beta isomers. However, the primary metabolic pathway for excretion of 17β-trenbolone and 17β-estradiol is oxidation to trendione and estrone, respectively, followed by a stereoselective reduction to 17α-trenbolone and 17α-estradiol, thus the alpha isomers are dominant in land applied manure. Sorption by five soils with a range in % organic carbon, % clay, clay type, and pH clearly show that sorption of β-isomers is approximately a factor of two greater than the α-isomers and that sorption is well correlated to soil organic carbon. The sorption mechanism responsible for stereoselective sorption will be discussed and probed using additional data for sorption by well characterized clays and dissolved organic material as well as chromatographic retention data.