Solid phase extractive preconcentration of thorium onto 5,7-dichloroquinoline-8-ol modified benzophenone

The preparation of solid reagent 5,7-dichloroquinoline-8-ol modified benzophenone for preconcentration of thorium is described. The thorium-5,7-dichloroquinoline-8-ol complex is quantitatively retained on benzophenone in the pH range 6.0–6.5. The solid mixture consisting of the metal complex together with benzophenone is dissolved in 5 ml of acetone and thorium content was established spectrophotometrically by using Arsenazo III procedure. Calibration graphs are rectilinear over the thorium concentration range 0.001–0.2 μg ml−1. Five replicate determinations of 20 μg of thorium present in 1 l of sample solution gave a mean absorbance of 0.320 with a relative standard deviation of 2.9%. The detection limit corresponding to three times the standard deviation of the blank was found to be 0.0005 μg ml−1. The developed procedure has been successfully utilized for the estimation of thorium content of pure Rare earth chloride solution collected from Indian Rare Earths (IRE) Limited, Alwaye.