Microdetermination of thorium using 5, 7-diiodo-8-hydroxyquinoline

An extractive spectrophotometric method for the trace determination of thorium is developed employing 5, 7-diiodo-8-hydroxyquinoline (in acetone) as complexing agent for the metal ion in aqueous medium. The yellow colored complex produced is quantitatively extracted into chloroform with absorption maximum at 409 nm. The method obeys Beer's law in the range 0.0-12.0 μg Th ml-1 having molar absorbitivity and Sandell's sensitivity values of 0.9 x 104 1 mol-1 cm-1 and 0.0256 μg Th cm-2 respectively. The ratio of metal to ligand in the extracted species is determined as 1:2. The method is free from the interference of a large number of diverse ions. Using the proposed procedure, the analysis of various samples has been carried out satisfactorily. (author)