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 develo ped for the determination of copper(II). It is based on the catalytic effec t of copper(II) on the oxidative coupling reaction of 3-methyl-2-benzothiaz olinone hydrazone with N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyani line to form a red compound (lambda(max)=525 nm) in the presence of hydroge n peroxide and pyridine as an activator. A higher sensitivity and sampling rate were achieved by adding benzyldimethyltetradecylammonium chloride (Zep hiramine) as a surfactant to this reaction system. The calibration graph fo r 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 o f 0.5 and 0.05 ng cm(-3) were 0.21 and 2.0%, respectively. The proposed met hod was successfully applied to the determination of copper in pepperbush.