Simultaneous Preconcentration of Cobalt, Nickel and Copper in Water Samples by Cloud Point Extraction Method and their Determination by Flame Atomic Absorption Spectrometry

A new cloud point extraction procedure was established for the simultaneous preconcentration and determination of cobalt(II), nickel(II), and copper(II) ions in water samples. After complexation with 2-(5-bromo-2-pyridylazo)-5- (diethylamino) phenol (5-Br-PADAP), the analytes could be competitively extracted in a surfactant octylphenoxy polyethoxyethanol (TritonX-114), prior to determination by flame atomic absorption spectrometry (FAAS). The effects of pH, the concentrations of chelating agent and surfactant, equilibration temperature and time, sample volume, etc on CPE were studied. The preconcentration factor obtained was 25 and the limits of detection (DL) obtained for cobalt(II), nickel(II), and copper(II) were 2.4, 1.7 and 1.5 ng·mL−1, respectively. Standard reference material of poplar leaf (GBW 07604) was analyzed by the proposed methods, giving results of cobalt(II), nickel(II), and copper(II) found contents in consistency with the standard values. The presented preconcentration procedure was successfully applied to determination cobalt(II), nickel(II), and copper(II) in water samples.