Study of spectrophotometric method for determination of trace copper after the separation and enrichment with solid phase extractant-microcrystalline phenolphthalein

A new method of using phenolphthalein loaded with 1-(2-pyridylazo)-2-naphthol (PAN) as solid phase extractant to separate and enrich trace copper in diverse water samples has been developed. The ef-fects of different parameters, such as the amounts of PAN and phenolphthalein, stirring time, various salts and metal ions on the enrichment yield of Cu(II) have been investigated to select the experimental conditions. Under the optimum conditions, Cu(II) can be totally adsorbed on the surface of microcrys-talline phenolphthalein. By controlling appropriate acidity (pH=1.0), Cu(II) is completely separated from Cd(II), Pb(II), Mn(II), Co(II), Fe(III), Ni(II), Al(III), Zn(II) and Hg(II) in the solution. The possible reaction mechanism of the enrichment of copper is discussed in detail in this paper. The detection limit of this proposed method is found to be 0.03 mg·L-1 with the enrichment factor of 200. The recovery is in a range of 96.8%―105%. The standard deviation is less than 2.5%. The proposed method has been successfully applied to the determination of trace copper in different water samples with satisfactory results.