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 (El) and 17 beta-estradiol (E2), and one synthetic estrogen, 17 alpha-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 E I, 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. E I 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). (c) 2006 Elsevier B.V. All rights reserved.