Study on the Catalytic Kinetic Spectrophotometric Determination of Trace Amounts of Iron(Ⅲ) and Its Reaction Mechanism
LIU Bing-zhi1, LUO Zhi-yong2*, ZHENG Huai-li1, JIANG Lei2
1. Key Laboratory of the Three Georges Reservoir Region Eco-Environment of Ministry of Education, Chongqing University, Chongqing 400045, China 2. School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044, China
Abstract：A catalytic kinetic spectrophotometric method, which is based on the catalytic effect of Fe(Ⅲ) on the fading reaction between potassium persulfate(K2S2O8) and methyl red(MR) in the solution of 0.30 mol·L-1 hydrochloric acid, for the determination of trace amounts of Fe(Ⅲ) has been investigated. A novel detection system, Fe(Ⅲ)-HCl-K2S2O8-MR, has been developed. The optimum experimental conditions for the determination of trace amounts of Fe(Ⅲ) were found on the basis of orthogonal test. The kinetics parameters and equation of this fading reaction of MR were studied. Its reaction mechanism was discussed. The results show that there is a good linear relationship between the variation of MR absorbance at the maximum absorption wavelength of 518 nm and the concentration of Fe(Ⅲ) under the optimum experimental conditions: ln(A0/A)=1.334 1+0.001 0, the correlation coefficient is 0.999 1. The kinetic research shows that the reaction order with respect to Fe(Ⅲ) is 1 and the overall fading reaction is a pseudo-first order reaction. The apparent activation energy of the fading reaction of MR is 69.88 kJ·mol-1. Furthermore, the catalytic effects of Fe(Ⅲ) on this fading reaction is confirmed by its reaction mechanism. This novel method for the determination of trace Fe(Ⅲ) has never previously been published so far. Trace amounts of Fe(Ⅲ) can be selectively determined by this catalytic kinetic spectrophotometric method with high precision and accuracy. This method is simple and its reagents used are cheap and available. Its sensitivity is higher than that of conventional spectrophtometry with detection limit of 0.005 mg·L-1. This detection system is stable. This proposed method has been applied to the determination of trace amounts of Fe(Ⅲ) in food and water samples with satisfactory results. Relative standard deviation of the detection results is 1.18%～2.11%. Average recovery rate of the detection results is 98.0%～104.0%.
刘冰枝1，罗志勇2*，郑怀礼1，蒋 磊2 . 痕量铁(Ⅲ)的催化光度法测定及动力学机制研究 [J]. 光谱学与光谱分析, 2016, 36(04): 1139-1144.
LIU Bing-zhi1, LUO Zhi-yong2*, ZHENG Huai-li1, JIANG Lei2 . Study on the Catalytic Kinetic Spectrophotometric Determination of Trace Amounts of Iron(Ⅲ) and Its Reaction Mechanism . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2016, 36(04): 1139-1144.
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