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

Abstract

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 (λmax=525 nm) in the presence of hydrogen peroxide and pyridine as an activator. A higher sensitivity and sampling rate were achieved by adding ben-zyldimethyltetradecylammonium 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.