Analysis of estrogens in river sediments by liquid chromatography–electrospray ionisation mass spectrometry: Comparison of tandem mass spectrometry and time-of-flight mass spectrometry

A method has been developed and optimised for the determination of two natural estrogens, estrone (E1) and 17β-estradiol (E2), and one synthetic estrogen, 17α-ethynylestradiol (EE2), in river sediments at the sub-ng/g level. This procedure includes microwave-assisted solvent extraction (MASE), solid-phase extraction and high-performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) with electrospray ionisation. Using sediments spiked with the three estrogens at 10 ng/g wet weight, efficient extraction (>92%) of all the three analytes was achieved by MASE, and whole-procedure recoveries ranged from 82 to 98%. Optimisation of the LC separation allowed for substantial reduction of ionisation suppression in the electrospray source to a final level of <18% suppression. Time-of-flight mass spectrometry (TOF-MS) and MS/MS were compared for the analysis of sediment extracts, with the latter technique proving to be the most selective. The method detection limits achieved by LC–MS/MS were 15, 30 and 40 pg/g for E1, E2 and EE2, respectively, which were 13-fold lower than those obtained by LC–TOF-MS. Analysis of river sediments collected from the River Ouse, UK, showed the presence of the natural estrogens at sub-ng/g level. E1 levels ranged from 0.40 ng/g (dry weight) to 3.30 ng/g while E2 levels ranged from <0.03 to 1.20 ng/g and EE2 was never detected (<0.04 ng/g).