Catalytic Kinetic Potentiometric Chemical Sensors Developed

The commonly used method of determining nitrite, Griess colorimetric method, has many disadvantages to the analysts and environment. A new catalytic kinetic method was described for the determination of trace amounts of NO[, based on its catalytic effect on the oxidation of iodide by potassium bromate. The reaction process was followed potentiometrically by an iodide ion-selective 27 KBrO~-KI ~ N07 electrode measurinQ~ the rate of variation of potential (AE) .Under suitable conditions, the indicator reaction is a first-order reaction and the AE is linearly related to the concentration of NO[. The optimum concentration of potassium bromate, potassium iodide and sulfuric acid are 8.OxlO3mol/L, 5.OxlO5mol/L and 1.4xlO2molIL respectively. The temperature is 30 0C and the reaction time is 1 5mm. The range of determination of nitrite is 0?1.63 x 10- 6mol/L and the detection limit is 5.62x109mo1/L. According to the experiment, the rate constant is linear with the catalyst concentration, which accords with the basic equation: RT AE=棔kt. The conditional activation energy E can be worked out by Arrhenius?equation. The E of catalyzed reaction is much less than that of uncatalvzed reaction and decreases with the increasing of catalyst concentration. The interference experiment indicates that most of ions have no influence on the determination of NO[ except Cu( II) and Fe(]Il). The method has been applied to the determination of trace nitrite in serum, meat, vegetables and grain. The results are smiliar to that of Griess method.