Determination of monomethylmercury cation in sediments by vacuum distillation followed by hydride derivatization and atomic fluorescence spectrometric detection

Abstract

This paper presents a method capable of quantitatively separating sub-nanogram amounts of monomethylmercury cation (MeHg+) and dimethylmercury from sediments by vacuum distillation at 40 °C and 6 μm Hg pressure followed by hydride derivatization and atomic fluorescence spectrometric detection. Concentrations of MeHg+ in Great Bay Estuarine sediments ranged from 2.2 to 7.3 ng g−1 (dry weight) with a 4.7 ng g−1 average for samples taken over nine weeks of the 1996 summer. The RSD for replicate determinations of a homogenized estuarine sediment is typically less than 6%. The detection limit for the routine determinations on MeHg+ is 0.2 ng g−1 dry weight of sediment. We validated the method by determining MeHg+ concentration in reference sediment S-19, by confirming our method against an established extraction method, and by recovering 85% of 10 ng MeHgCl spiked into estuarine sediments. This paper also includes significant improvements in the hydride derivatization method for mercury compounds relative to previous work with respect to faster analysis time and lower detection limits. © 1997 John Wiley & Sons, Ltd.