Study on Determination of Trace Copper(Ⅱ) by Catalytic Kinetic Discoloring Spectrophotometry
ZHENG Huai-li1, LONG Teng-rui2，ZHU Yan1
1. Faculty of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044, China 2. Faculty of Urban Construction and Environment Engineering, Chongqing University, Chongqing 400045, China
Abstract：A kinetic spectrophotometric method for the determination of trace Cu(Ⅱ) was developed in this paper. This method is based on the discoloring oxidation reaction between malachite green and hydrogen peroxide catalyzed by copper(Ⅱ) in the medium of HCl solution. The influential factors of reaction and the optimum conditions for the determination of Cu2+ were investigated in detail. The decrease in absorbance was measured at 615 nm at fixed time intervals. The linear determination range is between 0 and 22 μg·L-1 of copper(Ⅱ). A detection limit of 1.92 μg·L-1 is achieved. The catalytic and non-catalytic reactions are the first-order on copper(Ⅱ), in the reaction time interval 15-20 min at 70℃. The apparent activation energy of the catalytic reaction is 122.3 kJ·mol-1. The apparent rate is 7.70×10-4 s-1. The Relative Standard Deviations(RSD) are 1.16% and the recoveries are 98.3%-100.3%. By masking Fe(Ⅲ) ion with PO3-4, the method can be applied to the determination of copper in water sample and foodstuffs with satisfactory results.
[1] XI Dan-li, SUN Yu-sheng, LIU Xiu-ying(奚旦立，孙裕生，刘秀英). Environmental Monitoring(环境监测). Beijing(北京)：Higher Education Publishing House(高等教育出版社)，1994. 320. [2] HU Shou-kun, ZHENG Huai-li(胡守坤，郑怀礼). Metallurgical Analysis(冶金分析)，1990，10(3)：12. [3] ZHANG Shu-fang, QIN Mei, QU Li-qiang(张淑芳，秦 梅，曲立强). Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2002，22(1)：113. [4] XIA Chang-bin, HE Xiang-zhu(夏畅斌，何湘柱). Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2001，21(1)：90. [5] ZHENG Huai-li, ZHU Yan(郑怀礼，祝 艳). Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2002，22(6)：1075. [6] LIAO Li-fu, DENG Jian, YUAN Ya-li(廖立夫，邓 健，袁亚莉). Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2002，22(4)：659. [7] QI Yan-juan，WANG Xiao-ju, LI Hong-mei et al(齐艳娟，王晓菊，李红玫等). Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2002，22(3)：449. [8] ZHU Qing-ren, SUN Deng-ming, LI Hai-yan(朱庆仁，孙登明，李海燕). Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2002，22(1)：107. [9] FU Xian-cai, SHEN Wen-xia, YAO Tian-yang(傅献彩，沈文霞，姚天扬). Physical Chemistry(物理化学). Beijing(北京)：Higher Education Publishing House(高等教育出版社)，1990. 713. [10] HE Sui-yun, JIN Yun-yun, HE Fang(何燧云，金云云，何 方). Environmental Chemistry(环境化学). Shanghai(上海)：East China University of Science and Technology Publishing House(华东理工大学出版社)，2000. 108.
