Spectrophotometric determination of nitrite by the formation of bisazo dye

A sensitive spectrophotometric method for the determination of nitrogen dio xide in air, nitrate and nitrite in water, soil, radiator coolant and some analytical grade chemicals is described. The method is based on diazo coupl ing reaction, where 4-amino azobenzene: is treated with nitrite under acidi c condition in the presence of bromide ion and the formed diazonium salt co uples with resorcinol in acid medium. The formed bisazo dye has an absorpti on maxims at 550 nm under alkaline condition and obeys Beer's law over the range 0-16 mug of nitrite in overall aqueous volume of 25 mL. The system ob eys Beer's law over the range 0-3 mug nitrite, when extracted into toluene under ammoniacal condition (pH 9.0 +/- 0.5) and stripped to aqueous phase w ith 5 mt of 0.35 molar NaOH. The molar absorptivity of the colour system is 4.8 x 10(4) L. moL(-1). cm(-1).