Kinetic - spectrophotometric determination of trace amounts of resorcinol based on its inhibitory effect on the formaldehyde catalyzed reaction between bromate and neutral red

ABSTRACT A novel sensitive, simple and fast kinetic method for the determination of trace amounts of resorcinol (0.50 — 3.00 μg ml−1) based on its inhibitory effect on the formaldehyde catalyzed oxidation reaction of neutral red by bromate ion in acidic media is reported. The reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of neutral red in an inhibited reaction at 524 nm using a variable - time method. The detection limit is 0.38 μg ml−1 and the relative standard deviation of ten replicate measurements for 1 μg ml−1 of resorcinol is 4.2%. The procedure was successfully applied to the determination of resorcinol in resorcinol - S topical cream.