which should have miscibility with the extraction solvent and the aqueous sample. Different solvents (methanol, ethanol, acetonitrile and acetone) were taken into consideration. Ethanol was selected as dispersive solvent synthesizing each kind of situation for its best performance and the lowest toxicity. The effect of the volume of ethanol on the absorbance was shown in Fig. 2c. The maximum absorbance was obtained in the range of 200–300 lL. The optimum volume of ethanol was chosen at 200 lL in all experiments.