Quantification of estrogenic mycotoxins at the ng/L level in aqueous environmental samples using deuterated internal standards

Because of their pronounced estrogenicity, resorcyclic acid lactones (RALs) are of concern in aqueous environments even at the low ng/L level. Therefore, we developed an accurate, precise and sensitive HPLC-MS/MS method to detect these mycotoxins in different aqueous environmental samples. The compounds investigated included zearalenone (ZON), alpha- and beta-zearalenol, zearalanone as well as alpha- and beta-zearalanol. The use of isotope labelled internal standards (in this case deuterated RAL-analogues) ensured an accurate quantification of the target analytes, independent of matrix compounds interfering with the analytes during ionisation and analyte losses occurring during sample preparation. Sample enrichment was carried out by solid-phase extraction (SPE) using Supelclean Envi-18 cartridges. Absolute method recoveries for all analytes ranged from 95 to 108%, 70 to 102%, and 76 to 109%, method detection limits from 0.5 to 2.1 ng/L, 0.4 to 1.1 ng/L, and 0.8 to 12.4 ng/L and precision from 3 to 14%, 2 to 13% and 4 to 16% in drainage water, river water and wastewater treatment plant (WWTP) effluent, respectively. The method was applied to verify the emission of RALs from a Fusarium graminearum infested crop field into the drainage system. Zearalenone was present in drainage water in concentrations up to 30 ng/L. So far, none of the other five investigated compounds have been detected.