Spectrophotometric determination of cadmium(II) with dithizone and 1,10-phenanthroline

Cadmium(II) has been quantitatively separated from zinc(II) by an ion-pair extraction system. An ion-pair consisting of cadmium(II) and 1,10-phenanthroline (phen) was found to be preferentially extracted into chloroform from an aqueous chloride solution containing zinc(II). The extracted species in chloroform reacted with dithizone (H2Dz) to give the reddish mixed complex Cd(HDz)2(phen) having an absorption maximum at approximately 505 nm. The resulting calibration curve obeys Beer's law, the Sandell sensitivity being 0.0013 μg cm-2. The effect of diverse ions has been examined, and a new highly selective method for the spectrophotometric determination of trace amounts of cadmium in metallic zinc established. (author)