Determination of Copper in Human Urine by Cloud Point Extraction and Flame Atomic Absorption Spectrometry

This work reports novel cloud point extraction and preconcentration for the determination of copper in human urine by flame atomic absorption spectrometry. The method is based on the selective reaction of 2,9-dimethyl-1,10-phenanthroline (neocuproine) with Cu(I) to produce highly hydrophobic chelate that is extracted and preconcentrated using polyethylene glycol tert-octylphenyl ether (Triton X-114) as nonionic surfactant. Before the derivatization reaction, Cu(II) was reduced to Cu(I) by ascorbic acid. The effect of pH, concentration of the chelating agent and surfactant, equilibration temperature, and incubation time were investigated. Under optimum conditions, preconcentration of copper from 10mL of urine sample in the presence of 0.10% (w/v) Triton X-114 and 0.1mmol/L neocuproine at pH 5.9 permitted a limit of detection of 0.01 mu g/L for copper in urine. The relative standard deviation was less than 3.5% for copper concentrations from 0.5 to 100.0 mu g/L following cloud point extraction. The correlation coefficients of the calibration curves were higher than 0.999. The effects of matrix ions (cations and anions) on the recovery of copper were studied systematically. The use of flame atomic absorption spectrometry with certified reference material for the determination of copper in human urine yielded satisfactory results.