Combination of cloud point extraction and flame atomic absorption spectrometry for preconcentration and determination of nickel and manganese ions in water and food samples.

A simple, rapid, inexpensive, and nonpolluting cloud point extraction (CPE) technique has been improved for the preconcentration and determination of nickel and manganese. After complexation with p-nitrophenylazoresorcinol (Magneson I), the analytes could be competitively extracted in a surfactant octylphenoxy polyethoxyethanol (Triton X-114), prior to determination by flame atomic absorption spectrometry (FAAS). The effects of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and time on CPE were studied. Under the optimum conditions, preconcentration of a 25 mL sample solution permitted the detection of 2.7 ng mL(-1) Ni(2+) and 2.9 ng mL(-1) Mn(2+) with enrichment factors of 17 and 19 for Ni(2+) and Mn(2+), respectively. The developed method was applied to the determination of trace nickel and manganese in water and food samples with satisfactory results.