Determination of mercury and nickel by amperometric biosensor prepared with thermostable lactate dehydrogenase

Response of biosensor prepared with the thermostable bacterial LDH enzyme was analyzed in the presence of mercury and nickel. For electrode preparation, the enzyme was purified and immobilized on a gold sheet coated by PGA-pyrrole polymeric material. The working electrode was tested at increasing concentration of lactate in the presence of two different concentrations of mercury and nickel. Current response of biosensor decreased from 0.32 μA to 0.09 μA and 4.13 μA to 2.63 μA when 25×10−7 mmol/L mercury and 17×10−5 mmol/L nickel were included in the working solution, respectively. Sensitivity of the electrode decreased from 0.010 2 μA/(mmol·L−1) to 0.0043 μA/(mmol·L−1) in the presence of 25×10−7 mmol/L mercury. On the other hand, the presence of nickel did not result in a decrease in electrode sensitivity. The results pointed out that the prepared biosensor is useful to detect mercury in a sample containing both mercury and nickel together.