Selective determination method for measurement of methylmercury and ethylmercury in soil/sediment samples using high-performance liquid chromatography–chemiluminescence detection coupled with simple extraction technique

A method for the simultaneous determination of monomethylmercury (MeHg+) and monoethylmercury (EtHg+) in soil/sediment samples was developed. The method involves eluting mercury species from the soil/sediment samples using 5 M HCl containing 5 mM Pd2+ and 0.1 M Cu2+ and then extracting MeHg+ and EtHg+ into toluene as chlorides. These alkylmercury chlorides are then back-extracted into an aqueous EDTA solution, creating EDTA complexes. Finally, an emetine-dithiocarbamate (emetineCS2) solution is added to the EDTA solution to form emetineCS2–alkylmercury complexes. EmetineCS2–MeHg and emetineCS2–EtHg were separated using reverse-phase HPLC and then detected by the chemiluminescence reaction with tris(2,2′-bipyridine)ruthenium(III). The MeHg+ and EtHg+ calibration curves, using the peak height, were linear from 0.5 to 20 ng (as Hg). The detection limit was 0.16 ng/g (analyzing 1 g soil or sediment). The procedure was validated by analyzing a certified reference material (ERM CC580, estuarine sediment). The MeHg+ concentration determined using the proposed method was in good agreement with the certified value, and EtHg+ was detected in the reference material. A preliminary study of the relationship between environmental mercury concentrations and MeHg+ production was performed.