A modified disposable electrode formed by immobilization of glucose dehydrogenase (DHG) onto pyrocatechol violet (Pcv)-modified graphite pencil electrode (GPE) was proposed for the flow injection (FI) amperometric glucose biosensor. Cyclic voltammetric experiments show that Pcv illustrates a good electrocatalytic effect towards the oxidation of enzymatically produced NADH. Although electrocatalytic oxidation of enzymatically generated NADH at the DHG/Poly-Pcv/GPE was successfully performed at + 250 mV in FIA system, some molecules such as ascorbic acid (AA), dopamine (DA) and uric acid (UA) give a significant positive interference due to their oxidation at this working potential. To overcome these interferences, an injector filled with a pre-oxidant, sodium bismuthate (NaBiO3), was used in the FI amperometric glucose biosensor at the DHG/Poly-Pcv/GPE. Results showed that the interferences of these molecules were significantly minimized, because they were oxidized by NaBiO3 in the injector before reaching the electrode surface in the flow cell. The constructed biosensor showed that a linear calibration curve was obtained in the range between 5.0 mu M and 500 mu M glucose with a detection limit of 1.2 mu M. This proposed glucose biosensor including elimination of interferences of some oxidizable species was successfully applied to the real and artificial samples.