Direct speciation analysis of organic mercury in fish and kelp by on-line complexation and stacking using capillary electrophoresis

To determine organic mercury (Hg) species that could not be detected by ultraviolet (UV), a highly automated on-line complexation method was established, which combined with normal stacking by capillary electrophoresis-diode array detector. The approach was based on the fact that the compounds and complex reagent interacted to form hydrophilic chelates under the effect of the separation voltage, which was effectively separated and detected by UV. Key parameters, such as the type and concentration of complex reagent, separation voltage and so on were systematically investigated. Under the optimized conditions, the precision and repeatability were in the range of 0.16-3.31% and 0.17-1.21%, respectively. Furthermore, PhHg, EtHg and MeHg were effectively separated and determined in fresh fish (Silver carp) muscle and kelp (Kombu) with the recoveries of 84.63-111.39% and 75.68-114.76%, respectively. The proposed method had the advantages of easy-operating, cost-efficient, stable and reliable compared to off-line complexation method.