Photometric Determination of Microamounts of Fe(Ⅲ) Based on Its Catalytic Effect on the Color-fading Oxidation Reaction of Bromocresol Green with Potassium Bromate

It was found that in 0.2 mol·L-1 H3PO4 medium,the redox reaction between bromocresol green and potassium bromate was strongly catalyzed by the presence of microamounts of ferric ion,leading to an enhancement of color-fading of the bromocresol green,the absorption maximum of which was found at 440 nm.The reaction attained to equilibrium by heating in a water bath at 100 ℃ for 12 min.Linear relationship between values of ΔA(ΔA=A0-A) and concentration of Fe(Ⅲ) ion was obtained in the range of 7.2-1 800 μg per L of solution.Detection limit (3S/b) of the method was found to be 6.8 μg·L-1.In analyzing samples of water of different sources by the proposed method,results obtained were in consistency with the results found by FAAS method.Values of recovery and RSD′s (n=6) obtained were in the ranges of 95.5-100.1% and 2.8%-4.0% respectively.