On-line solid-phase extraction with on-support derivatization for high-sensitivity liquid chromatography tandem mass spectrometry of estrogens in influent/effluent of wastewater treatment plants

A solid-phase extraction coupled to liquid chromatography/tandem mass spectrometry for the determination of estrogens in sewage influent and effluent has been performed. The possibility of preparing estrogen derivatives directly on a solid-phase extraction bed in which the targeted analytes have been previously isolated and pre-concentrated was explored. This method uses an Oasis HLB column (2.1 mm × 20 mm i.d.) for on-line sample cleanup and derivatization support, and a Sunfire C18 column (150 mm × 2.1 mm i.d.) with a mobile phase consisting of acetonitrile–water–formic acid for separation. After sample introduction, some matrix interferences are removed by washing up SPE column with methanol–water. Phenolic hydroxyl group of estrogens is subsequently derivatized with dansyl chloride. Reaction takes place in the on-line solid-phase extraction column. The excess of reagent and other matrix interferences are then removed by a second washing. Dansylated estrogens are further back eluted and analyzed with HPLC–MS–MS. The optimized on-line protocol is emphasized owing to a low limit of quantification (1 ng L−1) is achieved with only around 1 mL of sample and a low sensitive MS instrument. Developed strategy has been demonstrated to be an improvement over existing methods due to its greater sensitivity and the low volume of matrix used and the total analysis time (extraction, derivatization, analysis) is less than 17 min.