Kinetic-Spectrophotometric Determination of Track Amounts of Nitrite Ion Based on Its Reduction Reaction with Thionine in Acidic Media

A simple, sensitive and rapid method for determination of trace amounts of nitrite ion in real samples is reported. The reaction is initiated by adding known volumes of a nitrite ion solution of identified concentration to acidic solutions of thionine which causes decolorizaiton of reagent with time. The absorbance changes is then monitored spectrophotometrically at lmax = 602nm at 25 °C. Calibration curve is linear in the range 0.005-1.500 mg/mL of nitrite ion. Many of cations and anions have no interfering effect but iodide, Mo(VI), W(VI) and  ions do interfere. The effect of interfering ions have been eliminated by the use of proper masking agents. This method was used to determine nitrite ion concentration in Karoon river water and foodstuffs such as susages.