在由pH 6.0磷酸盐缓冲溶液,0.5 mol·L-1硝酸钠及1.0×10-4mol·L-1中性红溶液组成的电解质溶液中,用循环伏安法以50 mV·s-1扫描速率在玻碳电极上先后在电位-1.3~1.9 V及-0.7~0.9 V范围内扫描6周及15周,从而制得聚中性红(PNR)膜修饰的玻碳电极.在此修饰电极上,亚硝酸根在电位0.872 V(vs.Ag/AgCl)处出现明显的氧化峰.据此并结合流动注射技术提出了安培法测定亚硝酸根的快速方法.方法的工作条件为① 采样环体积20 μL;② 载流0.025 mol·L-1磷酸盐缓冲溶液(pH 7.0)及0.5 mol·L-1氯化钾溶液;③ 载流流量1.8 mL·min-1;④ 工作电位0.95 V(vs.Ag/AgCl).峰电位值与亚硝酸根浓度在0.8~100 μmol·L-1间呈线性关系,其检出限(3σ)为1.0×10-7mol·L-1.以浓度为4.0×10-6mol·L-1亚硝酸根标准溶液平行测定8次,测得其相对标准偏差为3.6%.用此修饰电极连续检测24h,其电流信号保持稳定.此方法应用于分析火腿肠及自来水、湖水等样品,所得回收率在93.0%~112.0%之间.

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%.