Indirect determination of bromide by diffusion flow injection analysis with amperometric detection

Summary A rapid, indirect diffusion flow injection analysis (FIA) method with amperometric detection has been developed for the selective and sensitive determination of Br^–. The method is based on permanganate oxidation of Br^– to bromine. Bromine diffuses through a PTFE membrane and is quantified amperometrically at a platinum working electrode. Calibration graphs were linear up to the maximum concentration of Br^– investigated (10.0 mmol/l). The precision of the technique was better than a relative standard deviation of 0.7% at 10.0 mol/l, with a throughput of 30 samples per hour. The effects of temperature, acidity, working potential, composition of the reagent solution and interferents on the FIA signals were studied. The catalytic effect of Cl^– on the permanganate oxidation of the analyte was utilized to lower the detection limit to 1 mol/l (16 ng Br^–). Similar detection limits were achieved by combining the effects of higher acidity (4.0 mol/l H₂SO₄) and elevated temperatures (40°C). The method was successfully applied to the determination of Br^– in chloride and other reagents, as well as in natural waters.