Application of cinnamoyl derivative as a new ligand for dispersive liquid-liquid microextraction and spectrophotometric determination of cobalt

The method is based on the reaction of Co(II) with 3-[4-(dimethylamino)cinnamoyl]-4-hydroxy-6-methyl-2H-pyran-2-one (ligand) and a dimethylindocarbocyanine dye, followed by dispersive liquid-liquid microextraction of the ion associate formed and subsequent spectrophotometric detection. The appropriate experimental conditions were found to be: pH 9, 0.14 mM dye, toluene (extraction solvent) containing 2.25 mM of ligand, acetonitrile (dispersive solvent) and carbon tetrachloride (auxiliary solvent). Beer's law is obeyed in the range 0.06-0.42 mg/L of Co(II) at a wavelength of 558 nm. The limit of detection, calculated as three times the standard deviation of the blank test (n = 10), was found to be 9 mu g/L for Co(II). The method was applied to the determination of cobalt in spiked water samples and a vitamin B12 pharmaceutical injection.