In general, the extraction efficiency increases with increasing volume of extraction solvent and then decreases due to the dilution effect. Although the use of a lower volume of extraction solvent might lead to a better analytical response, it is not easy to handle, and it is difficult to remove the solidified drop from the surface of the aqueous phase in the amount necessary for the absorbance measurement. So 55 μL was preferred as the extraction solvent volume. Since the results obtained are close for both extraction solvents, 1-undecanol was selected for subsequent experiments due to the higher melting point.