Hollow fiber-based liquid–liquid–liquid microextraction combined with high-performance liquid chromatography for the speciation of organomercury

A novel and extremely highly sensitive method for the speciation of organomercury in sea food and environmental water samples was developed by hollow fiber liquid–liquid–liquid microextraction (LLLME) coupled to high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection at 254 nm. By the use of toluene filled the pores of the hollow fiber wall as the organic phase and Na2S2O3 aqueous solution in the lumen of hollow fiber as acceptor phase, the simultaneous preconcentration of methylmercury (MeHg), ethylmercury (EtHg), and phenylmercury (PhHg) could be realized, and the target mercury species in the post-extraction acceptor phase were directly injected into HPLC for their separation. The factors affecting on the liquid–liquid–liquid microextraction of three organomercury species, including organic solvent, the pH of donor phase, the concentration of complexing agent, extraction time and stirring rate were investigated and the optimal extraction conditions were established. With the consumption of 3.8 mL of sample solution, the enrichment factors were about 120, 215 and 350 for MeHg, EtHg, and PhHg, respectively. The limits of detection were in the range of 0.3–3.8 ng mL−1 (as Hg) with precisions (RSDs (%), c = 30 ng mL−1 (as Hg), n = 7) ranging from 6.4 to 8.9%. The developed technique was validated by analyzing a certified reference material (DORM-2, dogfish-muscle, NRCC) and an environmental water sample, and the analytical results were satisfactory.