Enzymatic determination of methylmercury traces using alcohol dehydrogenase from baker's yeast

Methylmercury as well as mercury (II) were found to be effective inhibitors of the catalytic activity of alcohol dehydrogenase from baker's yeast in the reaction of ethanol oxidation by nicotinamide adenine dinucleotide. It was stated that the methylmercury inhibitory action belonged to the non-competitive type, whereas Hg(II) inhibited the enzyme according to the mixed type. The inversely proportional dependence of the indicator reaction rate on the concentration of methylmercury allowed to develop an enzymatic procedure for its determination with a detection limit of 3 nM. The possibility of methylmercury determination in presence of mercury (II) and mercury (II) determination in presence of methylmercury (concentration ratios CH3Hg (+) :Hg(II) were 1:1 and 1:10, respectively) was shown. In the first case masking reagents, DEDTC or thiourea, were used to form stable complexes with Hg(II).