Atomic fluorescence spectrometric detection of methylmercury in seawater at sub ng L⁻¹ level by UV-induced atomization of gaseous methylethylmercury after NaBEt₄ derivatization with purge and trap preconcentration and gas chromatography separation

A sensitive method for methylmercury (MeHg) analysis in seawater by UV-induced atomization of methylethylmercury (MeHgEt) based on NaBEt₄ derivatization with purge and trap preconcentration and gas chromatography- atomic fluorescence spectrometry (GC-AFS) detection was developed. The UV atomizer was demonstrated successfully to atomize MeHgEt to Hg⁰ with low temperature (<45 °C) and low consumption (11 W). The effects of UV lamp power, the quartz tube length, the GC carrier gas flow rate and the NaBEt₄ concentration on MeHg determination were optimized. The relative standard deviations obtained from 0.25 ng L⁻¹ MeHg was 3.5%. The detection limits was calculated as 0.0002 ng L⁻¹ for MeHg, which not only reduced two orders of magnitude compared to the solid-phase extraction and cation or anion exchange column preconcentration methods, but also was comparable or even better than the thermal decomposition and dielectric barrier discharge (DBD) atomization methods after NaBEt₄ or NaBPr₄ derivatization with purge and trap preconcentration. In addition, compared with KBH₄ as reductant without preconcentration, the detection limit of this method was nearly reduced six orders of magnitude for MeHg. The accuracy of the proposed method was also validated by analyzing a certified reference sample (GBW08675) with a satisfactory result and successfully applied to the determination of MeHg in sub ng L⁻¹ level in different seawater samples.