Determination of glucocorticoids in sewage and river waters by ultra-high performance liquid chromatography-tandem mass spectrometry.

In this paper we present a method based on ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) combined with a solid-phase extraction to determine nine glucocorticoids in river waters and sewage. In addition, we attempt the chromatographic separation of two glucocorticoid epimers (betamethasone and dexamethasone) which until now had not been determined simultaneously in environmental matrices. For SPE, we have tested three commercial polymeric polar/non-polar balanced sorbents. The recoveries were close to or above 90% in rivers and sewage influents and effluents. The repeatability expressed as relative standard deviation (%RSD, n=3, 10 ng/L) was less than 8% in all cases. The method obtains LODs for glucocorticoids at low ng/L levels in aqueous environmental matrices (0.5-20 ng/L depending on the matrix and the analyte). The method was applied to determine these compounds in three Catalan rivers (Ebre, Ter and LLobregat) and two sewage treatment plants in the Tarragona area. Cortisone, cortisol, prednisone and prednisolone were frequently determined in influent sewage samples between 21 and 285 ng/L. Moreover, the two epimers were successfully determined below LOQs in some influent sewage samples.