Selective Cloud Point Extraction and Preconcentration of Trace Amounts of Cadmium Prior to Flame Atomic Absorption Spectrometric Determination

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 degrees C for 10 min. The surfactant-rich phase was diluted with 300 mu L of ethanol and 100 mu L 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 mu g L-1 of Cd(II). Analytical calibration curve was linear up to 250 mu g L-1 of cadmium and relative standard deviation was lower than 4% at 100 mu g 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.