Electroimmobilization of Nitrate Reductase into Polypyrrole Films on Screen Printed Carbon Electrode (SPCE) for Amperometric Detection of Nitrate

An amperometric nitrate biosensor was successfully constructed by the electroimmobilization of the enzyme nitrate reductase from Aspergillus niger with and without β-NADH, a co-factor, into conducting polypyrrole films on screen printed carbon electrode (SPCE). The best performance was registered by nitrate biosensor developed without the β-NADH electroimmobolize with nitrate reducatse on the SPCE. The formation of the optimum NaR-PPy composite on the SPCE was achieved with an applied potential of 0.9 Vs^-1 for 900s. The optimum amperometric response for nitrate was obtained in 0.1M potassium phosphate buffer, pH 7.5 with an applied potential of -0.1 Vs^-1 and 2mM β-NADH. Sensitivity of the nitrate biosensor was found to be in a linear range of 0.01-0.25mM with a regression coefficient of 0.97 and a relative standard deviation (RSD) of 6.6% (n=5).