Spectrophotometric determination of lead, zinc, and cadmium after extraction of their diethyldithiocarbamates into molten naphthalene and replacement by copper

A method is proposed for the extraction of lead, zinc, and cadmium as their diethyldithiocarbamates into molten naphthalene. These complexes are quantitatively extracted into molten naphthalene. After extraction, the solidified naphthalene containing the colorless complex of each of the above metals is dissolved in chloroform and the metal is replaced by copper(II) to develop a yellow color of copper(II) diethyldithiocarbamate. The absorbance is measured at 440 nm. Beer’s law is obeyed in the concentration range of 5.0–130.0 μg for lead, 3.0–60.0 μg for zinc, or 5.0–100.0 μg for cadmium in 10 ml of the final solution. The molar absorptivities (1 mol−1 cm−1) and Sandell sensitivities (μg/cm2) for lead, zinc, and cadmium are calculated to be 1.15×104, 0.0098, 1.11×104, 0.0059, and 1.15×104, 0.0098 respectively. Solutions containing 45.0μg of lead, 40.0μg of zinc, and 43.0μg of cadmium separately gave mean absorbances of 0.250, 0.620, and 0.440 with standard deviations of 0.0027, 0.0059, and 0.0038, respecti...