Flame Atomic Absorption Spectrometric Determination of Cd(II), Ni(II), Co(II) and Cu(II) in Tea and Water Samples after Simultaneous Preconentration of Dithizone Loaded on Naphthalene

A simultaneous preconcentration procedure for the determination of Cd(II), Ni(II), Co(II) and Cu(II) by atomic absorption spectrometry is described. The method is based on solid phase extraction of the metal ions on dithizone loaded on naphthalene in a mini-column, elution with nitric acid and determination by flame atomic absorption spectrometry. The sorption conditions including NaOH concentration, sample volume and the amount of dithizone were optimized in order to attain the highest sensitivity. The calibration graph was linear in the range of 0.5-75.0 ng ml-1 for Cd(II), 1.0-150.0 ng ml-1 for Ni(II), 1.0-150.0 ng ml-1 for Co(II) and 1.0-125.0 ng ml-1 for Cu(II) in the initial solution. The limit of detection based on 3Sb was 0.13, 0.32, 0.33 and 0.43 ng ml-1 for Cd(II), Ni(II), Co(II) and Cu(II), respectively. The relative standard deviations (R.S.D) for ten replicate measurements of 20 ng ml-1of Cd(II), 100 ng ml-1 of Ni(II), Co(II) and 75 ng ml-1 of Cu(II) were 3.46, 2.43, 2.45 and 3.26%, respectively. The method was applied to the determination of Cd(II), Ni(II), Co(II) and Cu(II) in black tea, tap and river water samples.