KINETIC SPECTROPHOTOMETRIC DETERMINATION OF LOW-LEVELS OF NITRITE BY CATALYTIC REACTION BETWEEN PYROGALLOL RED AND BROMATE

A kinetic spectrophotometric method for the determination of trace nit rite (0.003-1.000 mug/ml) based on its catalytic effect on the reactio n between potassium bromate and pyrogallol red in acidic media is desc ribed. The reaction is monitored spectrophotometrically by measuring t he decreasing colour of pyrogallol red at 467 nm by the fixed-time met hod. At a given time of 3.0 min at 30-degrees, the detection limit is 0.001 mug/ml and the relative standard deviation for 0.010 mug/ml nitr ite is 1.8% (n = 8). The method is free from most interferences, espec ially from large amounts of nitrate and ammonium. The procedure was su ccessfully applied to the determination of trace nitrite in natural wa ter without preconcentration.