Spectrophotometric Determination of Cadmium after Separation by Adsorption of Its Oxinate on

A procedure is presented for the spectrophotometric determination of cadmium after separation by adsorption of cadmium oxinate on microcrystallin naphthalene. A water-insoluble oxinate formed with cadmium is quantitatively adsorbed from aqueous solution with microcrystalline naphthalene. This oxinate has an absorption maximum at 395 nm. The optimum pH range for the adsorption is 5.8-9.2. The molar absorptivity is 4.5 x 103 l·mol-l.cm-l at 395 nm, the sensitivity being 2.5 x 10-2 μg of cadmium per cm-2 for an absorbance of 0.001. 87 Ten samples containing 100 μg of cadmium gave a mean absorbance of 0.403 with a relative standard deviation of 2.8%. Effect of optimum wavelength, amounts of reagent and naphthalene, digestion time, standing time, shaking time and diverse ions are studied