SIMULTANEOUS DETERMINATION OF COPPER AND IRON BY 2ND DERIVATIVE SPECTROPHOTOMETRY USING MIXTURES OF LIGANDS

A highly sensitive and selective second derivative spectrophotometric method has been developed for the determination of copper and iron in mixtures. The method is based on the separation of the analytes by liq uid-liquid extraction as picrate ion pairs. Iron-picrate, reacts in th e organic phase of DCE with 5-phenyl-3-(4-phenyl-2-pyridinyl)-1, 2,4-t riazine (PPT). Similarly the copper-picrate reacts with 2,9-dimethyl-4 ,7-diphenyl-1,10-phenantroline (bathocuproine). The extracts were eval uated directly by derivative spectrophotometric measurement, using the zero-crossing approach for determination of copper and graphic method for iron. Iron and copper were thus determined in the ranges 8-120 ng ml(-1) and 8-125 ng ml(-1), respectively, in the presence of one anot her. The detection limits achieved (3 sigma) were 2.9 ng ml(-1) of iro n and 2.8 ng ml(-1) of copper. The relative standard deviations were i n all instances less than 2.1%. The proposed method was applied to the determination of both analytes in river and tap water and the results were consistent with those provided by the AAS standard method. (C) 1 997 Elsevier Science B.V.