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

Abstract

A simultaneous preconcentration procedure for the d etermination of Cd(II), Ni(II), Co(II) and Cu(II) by atomic absorption spectrometry is described. The method is based on s olid phase extraction of the metal ions on dithizon e loaded on naphthalene in a mini-column, elution with nitric acid and determi nation by flame atomic absorption spectrometry. The sorption conditions including NaOH concentration, sample volume and the amount of dithizone were optimized in order to att ain the highest sensitivity. The calibration graph was linear in th e 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 d etection based on 3S b 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 -1 of 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 determi nation of Cd(II), Ni(II), Co(II) and Cu(II) in black tea, tap and river water samples.