Trace amounts of iron were determined by flow injection catalytic kinetic spectrophotometry,based on the catalytic effects of iron on the redox reaction between potassium bromate and 4,4′-tetramethyldiaminodiphenylmethane in the presence of potassium iodide in HAc-NaAc buffer solution.The measurements were conducted at 602nm of an unstable blue product of the reaction.Flow injection technique was utilized to precisely control the timing of merging and reaction of the reagents and samples.A stopped-flow approach was used to improve the sensitivity of the system.A detection limit of 2.6×10-9g/mL was achieved at a sampling frequency of 45/h.Calibration graphs were linear for ranges of 0～0.4mg/L for Fe(III).The proposed method was validated by the analysis of a national reference material and applied to the analyses of several water samples,with recoveries of 95.9%to 97.3%.
