SOLVENT EXTRACTION AND SPECTROPHOTOMETRIC DETERMINATION OF CADMIUM WITH 2, 2'-DIPYRIDYL-2-QUINOLYLHYDRAZONE

2, 2'-Dipyridyl-2-quinolylhydrazone(DPQH) is used for the spectrophotometric determination of traces of cadmium after the extraction as the iodide complex. Cadmium is extracted as the coordinationally solvated iodide complex with tributyl phosphate (TBP) in benzene from an aqueous buffered solution containing iodide and tartrate ions. The cadmium is converted to a strongly colored complex by the subsequent treatment of the extract with a DPQH solution in benzene in the presence of an ammonia-sodium hydroxide solution. The analytical species of interest has an absorption maximum at 510 nm and obeys Beer's law over the range 5 ×10-7-9 ×10-6 M cadmium in the organic phase. The effective molar absorptivity is 8.94×104 1 mole-1 cm-1 at 510 nm. The interfering metal ions can be effectively masked by thiosulfate, ascorbate, oxalate, thiourea, or cyanide.