Preconcentration procedure using cloud point extraction in the presence of electrolyte for cadmium determination by flame atomic absorption spectrometry

This paper describes a micelle-mediated phase separation in the presence of electrolyte as a preconcentration method for cadmium determination by flame atomic absorption spectrometry (FAAS). Cadmium was complexed with ammonium O,O-diethyldithiophosphate (DDTP) in an acidic medium (0.32 mol 1(-1) HCl) using Triton X-114 as surfactant and quantitatively extracted into a small volume (about 20 mu l) of the surfactant-rich phase after centrifugation. The chemical variables that affect the cloud point extraction, such as complexing time (0-20 min), Triton X 114 concentration (0.043-0.87% w/v) and complexing agent concentration (0.01-0.1 mol 1(-1)), were investigated. The cloud point is formed in the presence of NaCl at room temperature (25 degrees C), and the electrolyte concentration (0.5-5% w/v) was also investigated. Under optimized conditions, only 8 ml of sample was used in the presence of 0.043% w/v Triton X-114 and 1% (w/v) NaCl. This method permitted limits of detection and quantification of 0.9 mu g 1(-1) and 2.9 mu g 1(-1) Cd, respectively, and a linear calibration range from 3 to 400 mu g 1(-1) Cd. The proposed method was applied to Cd determination in physiological solutions (containing 0.9% (w/v) of NaCl), mineral water, lake water and cigarette samples (tobacco). (c) 2005 Elsevier B.V. All rights reserved.