A novel, environmentally friendly dispersive liquid-liquid microextraction procedure for the determination of copper

摘要

A novel, simple and environmentally friendly procedure for copper determination has been developed. The method is based on the formation of an ion associate of Cu(I) with 1,3,3-trimethyl-2-[5-(1,3,3-trimethyl-1,3-dihydroindol-2-ylidene)-penta-1,3-dienyl]-3H-indolium (DIDC) in the presence of chloride ions as ligand, followed by dispersive liquid-liquid microextraction (DLLME) of the formed ion associate into organic phase and UV-Vis spectrophotometric detection. The following experimental conditions were used: pH 3, 0.24molL~(-1) chloride ions, 0.06mmolL~(-1) DIDC. The effect of the nature of the extraction solvent, auxiliary solvent and disperser solvent used was studied. A mixture of amyl acetate, tetrachloromethane, and methanol in a 1:1:3v/v/v ratio was selected for the DLLME procedure. The absorbance of the coloured extracts at 640nm wavelength obeys Beer's law in the range 0.020-0.090mgL~(-1) of Cu. The limit of detection calculated from a blank test (n=10) based on 3s is 0.005mgL~(-1) of Cu. The developed procedure was applied to the analysis of water samples. The suggested DLLME is compared with two procedures previously reported from our laboratory based on (1) conventional liquid-liquid extraction, and (2) sequential injection extraction performed in a dual-valve sequential injection system. The advantages and disadvantages of each method are discussed.