1977 Volume 26 Issue 6 Pages 386-392
Metals react with various complexing reagents to form water-insoluble colored complexes, which are quantitatively extracted into molten naphthalene at a temperature above 81°C. The solidified mixture of metal complexes and naphthalene is separated from the aqueous solution, dried on the filter paper, and then dissolved in dimethylformamide by shaking. The trace amounts of metals in the solution are determined spectrophotometrically. The other factors such as wavelength, pH, amounts of complexing reagents and naphthalene, shaking time, and stability are studied and the molar absorptivities, sensitivities and relative standard deviations are evaluated. The extracted complexes are stable in naphthalene and naphthalene-dimethylformamide solution. This method is characterized by the facts that the equilibrium distribution in the two phases is attained rapidly and that the complexes are dissolved by contact with molten naphthalene or by slightly shaking. The mixtures of metal complexes and naphthalene are soluble in dimethylformamide which is miscible with water. Various metals were determined by using different complexing reagents as follows: Cu, Bi and Ni with DDTC, Cu, Bi and Co with APDC, Cu, Zn and Ni with 2-methyloxine, Cu with 5, 7-dichlorooxine and 5, 7-dibromooxine, Cu with α-benzoinoxime, Fe(III) and V(V) with N-benzoyl-phenylhydroxylamine and Ni with salicylaldoxime. Copper, zinc, magnesium, cadmium and cobalt were successfully determined by using oxine as the complexing reagent and by atomic absorption spectrophotometry.
