Analytical Sciences

Flow-Injection Determination of Copper(II) Based on Its Catalytic Effect on the Oxidative Coupling of 3-Methyl-2-benzothiazolinone Hydrazone with N-Ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyaniline in a Micellar Medium

Takuji KAWASHIMA* * , Hideyuki ITABASHI*, Norio TESHIMA*, Makoto KURIHARA* and Shigenori NAKANO**

*Laboratory of Analytical Chemistry, Department of Chemistry, University of Tsukuba, Tsukuba 305-8571, Japan
**Department of Environmental Sciences, Faculty of Education and Regional Sciences, Tottori University, Koyama-cho, Tottori 680-0945, Japan

A highly sensitive flow-injection spectrophotometric method has been developed for the determination of copper(II). It is based on the catalytic effect of copper(II) on the oxidative coupling reaction of 3-methyl-2-benzothiazolinone hydrazone with N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyaniline to form a red compound (lamda_max=525 nm) in the presence of hydrogen peroxide and pyridine as an activator. A higher sensitivity and sampling rate were achieved by adding benzyldimethyltetradecylammonium chloride (Zephiramine) as a surfactant to this reaction system. The calibration graph for copper(II) was linear over the range 0.005 - 0.75 ng cm^-3 at a rate of 40 samples h^-1. The relative standard deviations for ten determinations of 0.5 and 0.05 ng cm^-3 were 0.21 and 2.0%, respectively. The proposed method was successfully applied to the determination of copper in pepperbush. (Keywords: Flow-injection photometric method; catalytic reaction, copper determination, 3-methyl-2-benzothiazolinone hydrazone, N-ethyl-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyaniline, Zephiramine)

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