Spectrophotometric determination of copper in waste water using liquid-liquid extraction in a flow-injection system

A flow-injection procedure for the determination of copper in waste water is described. The procedure is based on the formation of an ion-pair between tetrabutylammonium and the tetrathiocyanatocuprate(II) anion. This ion-pair is extracted with chloroform, and the absorbance of the organic phase is measured at 485 nm. Concentrations of copper greater than or equal to0.4 mg L-1 can be detected with a linear application range of between 0.5 and 25 mg L-1, a relative standard deviation of 2.3% (0.8 mg L-1, n=10) and a sampling frequency of 30 h(-1). Under the proposed working conditions, only Ni(II) and Pd(II) interfere at molar ratios Ni(II)/Cu(II) greater than or equal to 50 and Pd(II)/Cu(II) greater than or equal to 100.