FI-Amperometric Determination of Traces of Nitrite with Glassy Carbon Electrode Modified by Poly-Neutral Red Film

Poly neutral red (PNR) film modified GCE was prepared by cyclic voltammetry (CV) with scanning rate of 50 mV·s-1 in an electrolyte containing PBS of pH 6.0,0.5 mol·L-1 NaNO3 and 1.0×10-4mol·L-1 neutral red solution for 6 cycles at -1.3-1.9 V (vs.Ag/AgCl) and 15 cycles at -0.7-0.9 V.A significant oxidation peak of nitrite ion was observed at the potential of 0.872 V at the PNR modified electrode.By using flow injection technique,a rapid method of amperometric determination nitrite was proposed with the following working parameters: ① vol.of sampling ring 20 μL;② carrying solution 0.025 mol·L-1 PBS (pH 7.0)+0.5 mol·L-1 KCl solution;③ flow rate of the carrier 1.8 mL·min-1;④ working potential 0.95 V (vs.Ag/AgCl).Linear relationship between values of peak current and concentration of nitrite was obtained in the range of 0.8-100 μmol·L-1,with detection limit (3σ) of 1.0×10-7mol·L-1.Eight replicate determinations of NO-2 standard solution of 4.0×10-6mol·L-1 were carried out by the proposed method,giving RSD of 3.6%,and the current signals were kept stable for 24 h in continuous operation with the modified electrode.In applying this method to the analysis of samples of ham sausages and water,values of recovery found were in the range of 93.0%-112.0%.