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

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 (lambda(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.