Separation/preconcentration and determination of cadmium ions by solidification of floating organic drop microextraction and FI-AAS

A simple and selective method for the separation and preconcentration of cadmium in water samples based on solidified floating organic drop microextraction (SFODME) was developed. The cadmium ion in aqueous solution was converted to Cdl(4)(2-) and was then extracted with 160 mu L of 1-undecanol containing cationic surfactant of methyltrioctylammonium chloride (0.2 mol/L). When the extraction was completed, the sample vial was cooled in an ice bath for 5 min. The solidified extract was transferred into a conical vial where it melted immediately. It was then diluted to 250 mu L upon addition of ethanol, and 100 mu L of it was analyzed by How injection flame atomic absorption spectrometry (FI-FAAS). Factors that influence the extraction and ion pair formation, such as pH, concentration of iodide and methyltrioctylammonium chloride, extraction time, sample volume, and ionic strength were optimized. Under the optimized conditions, a preconcentration factor of 640, detection limit of 0.0079 mu g/L and good relative standard deviation of +/-5.4% at 5 mu g/L were obtained. The procedure was applied to tap water, well water. and sea water; and accuracy was assessed through recovery experiment and independent analysis by graphite atomic absorption spectrometry. The accuracy was also evaluated through analyses of certified reference ore. (C) 2009 Elsevier B.V. All rights reserved.