Flotation-spectrophotometric method for separation and determination of trace amounts of copper

A flotation-spectrophotometric method for the determination of cu 2+ has been developed. the flotation process is based on the formation of a ternary ion-associate between cu2+,methylthymol blue (mtb) and cetyltrimethylammonium bromide (ctab) which is floated at the interface of aqueous phase and n-hexane by shaking in a separating funnel. the aqueous solution is discarded and the adsorbed ion associate (cu 2+-mtb-cta+) on to the wall of a separating funnel is dissolved in a small volume of methanol solvent and its absorbance is measured at 556 nm. the apparent molar absorptivity (ε) of the ion associate was determined to be 6.1×104 l mol-1 cm-1. the calibration curve was linear in the concentration range of 10-400 ng ml -1 of cu2+ with a correlation coefficient of 0.9994. the limit of detection (lod) was 6.7 ng ml-1. the relative standard deviation (rsd) for 50 and 300 ng ml-1 of cu2+ was 3.9% and 1.3% (n=7),respectively. the method was successfully applied to the determination of cu in water samples from water treatment process of ramin power plant,iran.