Ligandless cloud point extraction for trace nickel determination in water samples by flame atomic absorption spectrometry

Abstract

A very simple and ligandless cloud point extraction (CPE) methodology has been developed for the preconcentration of trace amounts of nickel as a prior step to its determination by flame atomic absorption spectrometry (FAAS). The method is based on the extraction of nickel at pH 10 by using non-ionic surfactant polyethyleneglycol mono-p-nonylphenylether (PONPE 7.5) without adding any chelating agent. Several variables affecting the extraction efficiency were investigated and optimized. The limit of detection (LOD) and limit of quantification (LOQ) values of nickel for the preconcentration of 50 mL of aqueous solution were 0.5 μg L-1 and 1.6 μg L-1, respectively. The relative standard deviation (RSD) for six replicate determinations at 50 and 80 μg L-1 of Ni were 2.67% and 1.97%, respectively. The calibration graph using the preconcentration system for nickel was linear with a correlation coefficient r = 0.9941. To validate the proposed method a standard reference material NIST SRM 1643e (trace elements in water) was analyzed and the result was in good agreement with the certified value. The proposed method was successfully applied to determination of trace amounts of nickel in water samples. © 2011.