Dielectric barrier discharge induced atomization of gaseous methylethylmercury after NaBEt4 derivatization with purge and trap preconcentration for methylmercury determination in seawater by GC-AFS

Abstract

A novel method suitable for methylmercury (CH3Hg) analysis in seawater by gas chromatography (GC)-atomic fluorescence spectrometry (AFS) based on dielectric barrier discharge (DBD) induced atomization of gaseous methylethylmercury (CH3HgC2H5) after sodium tetraethylborate (NaBEt4) derivatization with purge and trap preconcentration was developed in this work. In the proposed method, with NaBEt4 used as derivatization reagent, the nonvolatile CH3Hg could be converted to the gaseous CH3HgC2H5 and trapped in a quartz tube with Tenax sorbent for preconcentration. A DBD atomizer was employed for the atomization of CH3HgC2H5 to Hg0 between the GC separation and AFS detection instead of the conventional thermal decomposition atomizer, which had not been reported before. The DBD atomizer not only produces a comparable atomization efficiency for CH3HgC2H5 to the thermal decomposition atomizer, but also can be operated at room temperature with low power consumption (5 W). The effects of DBD input discharge voltage, DBD discharge distance, N2 gas purge time, and thermal desorption time on CH3Hg determination were evaluated. The method provided good reproducibility (RSD, 2.0%) and low detection limits of CH3Hg (LOD, 0.0008 ng L−1). The proposed method was validated by the analysis of a certified reference material (GBW08675) and successfully applied to the determination of CH3Hg in sub ng L−1 level in different seawater samples.