NEW METHOD FOR DETECTING METHYLMERCURY BY ITS ENZYMATIC CONVERSION TO METHANE

A new method is suggested for determining methylmercury in biological samples. The determination is based on the use of whole cells of a "broad-spectrum" mercury-resistant bacterium, Pseudomonas putida, strain FB1, which is induced to produce the enzymes organomercurial lyase and mercuric reductase. These biocatalysts convert organomercurials to elemental mercury and their derivative hydrocarbons. The extraction procedure for methylmercury in biological samples followed the conventional toluene extraction method, which is retained until methylmercury is concentrated in an aqueous phase containing 0.01 M Na2S2O3. This solution is mixed with bacterial cells in exponential growth phase and then incubated in microreaction vessels. A complete biological degradation of methylmercury to methane occurs. The efficiency of derivatization depends on the organomercurial concentration, the incubation time, and the cell density. The detection limit is 15 ng of methylmercury in 1 g of biological tissue and the coefficient of variation is 1.9% in 10 replicate samples with 100 ng/mL.