Gas-assisted dispersive liquid-phase microextraction using ionic liquid as extracting solvent for spectrophotometric speciation of copper.

ABSTRACT

Gas-assisted dispersive liquid-phase microextraction (GA-DLPME) has been developed for preconcentration and spectrophotometric determination of copper ion in different water samples. The ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate and argon gas, respectively, were used as the extracting solvent and disperser. The procedure was based on direct reduction of Cu(II) to Cu(I) by hydroxylamine hydrochloride, followed by extracting Cu(I) into ionic liquid phase by using neocuproine as the chelating agent. Several experimental variables that affected the GA-DLPME efficiency were investigated and optimized. Under the optimum experimental conditions (IL volume, 50µL; pH, 6.0; acetate buffer, 1.5molL(-1); reducing agent concentration, 0.2molL(-1); NC concentration, 120µgmL(-1); Ar gas bubbling time, 6min; argon flow rate, 1Lmin(-1); NaCl concentration, 6% w/w; and centrifugation time, 3min), the calibration graph was linear over the concentration range of 0.30-2.00µgmL(-1) copper ion with a limit of detection of 0.07µgmL(-1). Relative standard deviation for five replicate determinations of 1.0µgmL(-1) copper ion was found to be 3.9%. The developed method was successfully applied to determination of both Cu(I) and Cu(II) species in water samples.