DETERMINATION OF BROMIDE IN SODIUM-CHLORIDE MATRICES BY FLOW-INJECTION ANALYSIS USING BLANK PEAK ELIMINATION AND KINETIC DISCRIMINATION

Flow-injection analysis was applied to the determination of bromide in a sodium chloride matrix. The method is based on oxidation of bromide with chloramine-T to bromine, followed by reaction with phenol red to form bromophenol blue, the absorbance of which is measured spectrophotometrically. The interference of chloride, forming chlorinated reaction products at a much slower rate than the reaction with bromophenol blue, is prevented in flow-injection analysis because of the short reaction times. The influence of blank peaks, which appear because of the difference in the refractive indices of the aqueous carrier solution and the sample solution, is eliminated by use of a large sample injection volume. The limit of quantification of bromide in sodium chloride is 1.0 mg kg-1. The relative standard deviation at a level of 30-50 mg Br- kg-1 is better than 1%. The repeatibility and reproducibility were determined in a round-robin test. The characteristics of the method such as calibration, selectivity and ruggedness are described. The sample throughput is about 60 h-1.