Spectrophotometric determination of nitrite by the formation of bisazo dye

Abstract

A sensitive spectrophotometric method for the determination of nitrogen dioxide in air, nitrate and nitrite in water, soil, radiator coolant and some analytical grade chemicals is described. The method is based on diazo coupling reaction, where 4-amino azobenzene is treated with nitrite under acidic condition in the presence of bromide ion and the formed diazonium salt couples with resorcinol in acid medium. The formed bisazo dye has an

absorption maxima at 550 nm under alkaline condition and obeys Beer's law over the range 0-16 μg<i> </i>of nitrite in overall aqueous volume of 25 mL . The system obeys Beer's law over the range 0-3 μg nitrite, when extracted into toluene under ammoniacal condition (<i>p</i>H 9.0 ± 0.5) and stripped to aqueous phase with 5 mL of 0.35 molar NaOH. The molar absorptivity of the colour system is 4.8×10⁴ L. mol^-1 cm^-1.