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 nitrite (0.003-1.000 mug/ml) based on its catalytic effect on the reaction between potassium bromate and pyrogallol red in acidic media is described. The reaction is monitored spectrophotometrically by measuring the decreasing colour of pyrogallol red at 467 nm by the fixed-time method. 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 nitrite is 1.8% (n = 8). The method is free from most interferences, especially from large amounts of nitrate and ammonium. The procedure was successfully applied to the determination of trace nitrite in natural water without preconcentration.