Ultrasound-assisted cloud point extraction coupled with flame atomic absorption spectrometry for the determination of lead and cadmium in water samples

Abstract

A new method based on ultrasound-assisted cloud point extraction (UA-CPE) using the mixture of non-ionic surfactant alkylphenol ethoxylate NP-7 and alkylphenol ethoxylate NP-9 for the preconcentration of trace amounts of lead (Pb) and cadmium (Cd) in water samples prior to determination by FAAS has been developed. In this method, Pb and Cd react with ammonium pyrrolidinedithiocarbamate (APDC), yielding hydrophobic complexes, which then are extracted into the surfactant-rich phase. Compared with the traditional CPE, faster phase separation and higher recovery were obtained using the ultrasound-assisted process and a series of non-ionic nonyl phenol ethoxylate surfactants in the present UA-CPE. Variable parameters affecting the CPE procedure were evaluated and optimized. Under the optimized conditions, the calibration graph was linear in the range of 10–500 μg L⁻¹ for Pb and Cd. The detection limits were 0.5 μg L⁻¹ and 0.28 μg L⁻¹ with relative standard deviations of 2.6% and 3.4% for Pb and Cd, respectively. The enrichment factors were 57 and 63 for Pb and Cd, respectively, for 10 mL of preconcentrated solution. The method was successfully applied to the determination of Pb and Cd in water samples.