Selective cloud point extraction and preconcentration of trace amounts of cadmium prior to flame atomic absorption spectrometric determination

Abstract

Cloud point extraction (CPE) is proposed as a separation and preconcentration procedure for determination of cadmium in water samples by flow injection flame atomic absorption spectrometry (FI-FAAS). The cadmium ion in aqueous solution was converted to [CdI4]2- and its charge was neutralized through ion-pair formation with methyltrioctylammonium cation in the presence of Triton X-114 as a non ionic surfactant. Phase separation was achieved by heating the mixture to 80 ºC for 10 min. The surfactant-rich phase was diluted with 300 µL of ethanol and 100 µL of it was analysed by FI-FAAS. The parameters affecting the ion-pair formation and extraction steps were optimized. Under optimum condition, preconcentration of 35 mL of sample in the presence of 0.04% (v/v) of Triton X- 114 led to a detection limit of 0.3 µg L-1 of Cd(II). Analytical calibration curve was linear up to 250 µg L-1 of cadmium and relative standard deviation was lower than 4% at 100 µg L-1 level. The procedure affords recoveries in the range of 95-102%. The procedure was successfully applied to the determination of Cd in tap water, sea water and certified reference copper concentrate.