Determination of endogenous and exogenous estrogens in effluents from sewage treatment plants at the ng/L-level

An analytical method for the determination of the major endogenous and exogenous estrogenic steriods in effluent water samples of sewage treatment plants (STPs) with a LOQ down to 1 ng/L and below has been developed. The exogenous estrogen 17 alpha-ethynylestradiol, frequently used as estrogenic component in oral contraceptives, and the endogenous estrogen 17 beta-estradiol show the highest estrogenic potential, therefore they were part of our target compounds. In addition, the content of the synthetic gestagen levonorgestrel, also often administered in oral contraceptives, was determined. A solid-phase extraction system for high volume sampling of water up to 25 L was implemented. Two types of adsorbent, Amberlite XAD 2 and a mixture of LiChrolut EN/Bondesil C-18, respectively, were tested for their extraction efficiency of these polar analytes. Recovery rates with LiChrolut EN/ Bondesil C-18 ranged up to 94%, whereas sampling on XAD 2 led only to poor recoveries below 40%. After a liquid chromatographic clean-up step on silicagel the steroids were converted into their trimethylsilyl-ethers by the reaction with MSTFA/TMSI (N-methyl-N-trirnethylsilyl-2,2,2-trifluoroacetamide, trimethylsilyliodide) and were then determined by HRGC/MS in the selected ion mode. A limit of quantification over the whole procedure of at least 1 ng/L was reached for all analytes. In several effluent samples the input of estrogens by the STP of the cities Ulm and New Ulm into the river Danube was characterised. The concentrations commonly found ranged from 1 ng/L up to 13 ng/L, depending on the respective steroid.