Flow-injection Spectrophotometric Determination of Copper Based on the Solvent Extraction of the Ion Associate of Dibromocuprate(I) with Cationic Dyes

Abstract

Copper in water was determined by a spectrophotometric method involving flow injection coupled with solvent extraction. An ion associate formed between dihalogenocuprate(I)ion and a dye cation was extracted into an organic solvent and the absorbance of the separated organic phase was measured. Three triphenylmethane dyes and three analogues of the azo dye 4- (4-diethylaminophenylazo) N-alkylpyridinium cation were examined as counter cations, and three kinds of dihalogenocuprate(I) ions and various kinds of extraction solvents were examnied. The best extraction system for FIA was the system CuBr₂ ^--PEP⁺ (the propyl derivative of the azo dye)-chlorobenzene. The carrier stream was 0.02 M L-ascorbic acid solution, the reagent stream contained 10^-4 M PEP⁺ and O.03 M KBr (pH 5), and the extraction solvent stream was chlorobenzene. The organic phase was separated with a polytetrafluoroethylene porous membrane. The sampling rate was 30 per hour. The calibration graph was linear at concentrations below 3×10-5 M using samples of 300 id. The detection limit corresponding to a signal to noise ratio of 3 was 2×10^-8 M, and the relative standard deviation for 11 measurements of 1×10^-6 M copper solution was 0.7%. Anionic surfactants were separated from the peak of copper by using a 3 m dilution coil.