Catalytic Kinetic Spectrophotometric Determination of Trace Iron(III) with 2-(1,3,4-Triazolylazo)-5Diethylaminobenzoic Acid and Hydrogen Peroxide

A new catalytic kinetic method for the determination of trace Fe(Ⅲ) was established based on the catalytic action of Fe(Ⅲ) on the oxidative fading reaction between 2-(1,3,4-triazolylazo)-5-diethylaminobenzoic acid(TZDBA) and hydrogen peroxide.In HAc-NaAc buffer solution with pH=4.0,the maximum absorption wavelength of the fading system was 488 nm.The apparent activation energy Ea of the catalytic reaction was 42.10 kJ/mol and the rate constant k was 8.57×10-4 s-1.The calibration curve was linear in the range of 0.01～0.20 mg/L for Fe(Ⅲ),and the linear regression equation was △A=4.3611c+0.006(c:mg/L) with the correlation coefficient of 0.9992.The detection limit was 6.62×10-10 g/mL.The method was applied to the determination of trace iron in flour and hair samples.The results were in good agreement with the values obtained by atomic absorption spectrometry.The relative standard deviations of this method was between 1.88%～ 2.84%(n=6) and recoveries were in the range of 96.4%～104.4%.