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 (CH 3 Hg) analysis in seawater by gas chromatography (GC)-atomic fluorescence spectrometry (AFS) based on dielectric barrier discharge (DBD) induced atomization of gaseous methylethylmercury (CH 3 HgC 2 H 5 ) after sodium tetraethylborate (NaBEt 4 ) derivatization with purge and trap preconcentration was developed in this work. In the proposed method, with NaBEt 4 used as derivatization reagent, the nonvolatile CH 3 Hg could be converted to the gaseous CH 3 HgC 2 H 5 and trapped in a quartz tube with Tenax sorbent for preconcentration. A DBD atomizer was employed for the atomization of CH 3 HgC 2 H 5 to Hg 0 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 CH 3 HgC 2 H 5 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, N 2 gas purge time, and thermal desorption time on CH 3 Hg determination were evaluated. The method provided good reproducibility (RSD, 2.0%) and low detection limits of CH 3 Hg (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 CH 3 Hg in sub ng L −1 level in different seawater samples.