l-Glutamate biosensor based on l-glutamate oxidase immobilized onto ZnO nanorods/polypyrrole modified pencil graphite electrode

A method is described for the construction of a highly sensitive electrochemical biosensor for the detection of l-glutamate. Such a biosensor is based on immobilization of glutamate oxidase (GluOx) onto zinc oxide nanorods (ZnONRs)/polypyrrole (PPy) composite. This composite was electro-deposited onto a pencil graphite (PG) electrode. The enzyme electrode was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), Fourier transform infra-red spectroscopy (FTIR) and cyclic voltammetry (CV). The biosensor showed optimum response at pH 8.5 (0.1 M Tris-HCl buffer) and 30 °C, when operated at 20 mV s−1. The biosensor exhibited excellent sensitivity (detection limit as 0.18 nM), fast response time (less than 5 s) and wide linear range (0.02-500 μM). Analytical recovery of added l-glutamate (20 and 40 μM) in commercial Chinese soup were 95.40 and 97.56% respectively .The within batch and between batch coefficients of variation (CV) in measurement of l-glutamate in commercial Chinese soup were 2.35% and 4.5% respectively. The enzyme electrode lost 30% of its initial activity after 100 uses over a period of 90 days, when stored at 4 °C.