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

Abstract

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 5M HCl containing 5mM Pd(2+) and 0.1M Cu(2+) 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 20ng (as Hg). The detection limit was 0.16ng/g (analyzing 1g 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.