1983 Volume 1983 Issue 4 Pages 513-517
The formation constants (K) of 1 to 1 metal chelates of 2-[1-(2-methoxy-5-sulfophenyl)-3-phenyl-5-formazano]benzoic acid (CMF) with cobalt(II), nickel(II), copper(II) and palladium(II) have been determined spectrophotometrically in aqueous solution at 1, 0.1(NaClO4)and 26±1°C. The formation constants obtained decrease in the order Cu>Pd>Ni>Co, the log K values being 18.1, 14.90, 11.50 and 11.25, respectively. The copper chelate has an absorption maximum at 580 nm and the maximum absorbance is obtained in the pH range 3.5 to 9.5. The calibration curve obeys Beer's law over the range 0 to 65 μg·25 cm-3 of copper; the molar absorption coefficient of the chelate and Sandell's sensitivity are 2.1 x 104dm-3·cm-3and 3.O× 10-3μg·cm-2, respectively. The relative standard deviation of the absorbance was 3.37x 10-3 for 1.2 μg·cm-3 of copper. A large amount of Co(II), Ni(II), Pd(II) and Fe(III)interfered with the determination. The proposed procedure is as follows: To the sample solution containing up to 65 aug in a 25 cm3 volumetric flask, add 5 cm3 of acetate buffer (pH 3.5) and 2 cm3 of O.1% CMF. Dilute to the mark with water and measure the absorbance at 580 nm against the reagent blank as a reference.
The proposed method which is highly selective and rapid is applicable to the analysis of copper in zinc alloy die casting, food (chiken eggs, mother's milk) and biological materials (rat liver, kidney, blood, and bovine liver).
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