Cloud point preconcentration and flame atomic absorption spectrometry: application to the determination of nickel and zinc

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Abstract
A simple and versatile method for the preconcentration of trace amounts of nickel and zinc is proposed. The method, which does not require the use of organic solvents, is based on the phase separation phenomenon undergone by aqueous solutions of non-ionic surfactants and can be used as a prior step to the determination of these elements by flame atomic absorption spectrometry. 1-(2-Pyridylazo)-2-naphthol (PAN) and Triton X-114 were used as hydrophobic ligand and non-ionic surfactant, respectively. The chemical variables affecting the separation phase and the viscosity affecting the detection process were optimized. Under the experimental conditions used, preconcentration of only 10 ml of sample in the presence of 0.1% Triton X-114 permitted the detection of 8 ppb of zinc and 6 ppb of nickel. The proposed procedure was applied to the determination of both ions in different water samples.