An extractive spectrophotometric method for the determination of nitrite using fluorescein amine isomer I

A sensitive spectrophotometric method for the determination of nitrite using fluorescein amine isomer I is described. The method is based on the formation of azido derivative of fluorescein amine isomer I, which is selectively extracted into 20% iso amyl alcohol in toluene and is stripped to aqueous phase using NaOH. Formation of the azido derivative depends on nitrite concentration and the system obeys Beer's law in the range 0-0.4 ppm of nitrite at 495 nm. The molar absorptivity of the colour system is 6.67 x 104 L mol-1 cm-1 with a relative standard deviation of 3% for 10 determinations at 1 μg of nitrite. The proposed method is successfully applied for the determination of nitrite and nitrate in soil, water and radiator coolant sample. NO2 gas in a laboratory fume cupboard is determined after fixing it as nitrite in sodium arsenite absorber solution.