Electrochemistry and electrophoresis of mercury cysteine and ditizone complexes
There are various mercury species in the environment and their toxicity and availability relies on their chemical form and oxidation states. Inorganic and organic mercury is found to co-exist in water and body tissue of some organisms. Among them inorganic mercury has a lower toxicity than the organic mercury. Methyl mercury (CH3Hg+) is the most toxic species found in the environment because it can enter the food chain accumulating and contaminating humans. Hence the total mercury concentration does not reflect the important information and thus the needs for the development of methods for the simultaneously separating and determination of mercury species. A study of the electrochemistry of mercury and organo mercury complexes with cysteine and dithizone indicated the formation of stable complexes, which can be utilized for the determination of the species in environmental matrices. Cyclic voltammetry is used to determine the electrochemical properties of the complexes. A technique based on capillary electrophoresis and amperometric detection (CE-AD) has been developed for the speciation of mercury. This technique has the capability to detect mercury species that are electrochemically active. Using capillary electrophoresis in combination with electrochemical detection makes speciation of the complexes possible at lower than normal concentrations. For CE-AD the detection limits were 0.005 μg/L for Hg2+ and 0.4 μg/L for MeHg+. These detection sensitivities are attractive for environmental monitoring.