Sensitive Spectrophotometric Determinaton of Thorium(Iv) using 5-Bromo Salicylaldehyde Isonicotinoyl Hydrazone(5-Brsainh).

Simple and sensitive direct and derivative spectrophotometric method for the determination of thorium(IV) is reported.The method is
based on the formation of yellowish green coloured complex of a stoichometric ratio 1:1 between thorium and 5-bromo salicylaldehyd 
isonicotinoyl hydrazone(5-BrSAINH) at pH 5.0. The maximum absorbance of [Th(IV)-5-BrSAINH] complex was measured at
385nm.Under the optical conditions , Beer’s law is obeyed over the range 1.16-15.08μg mL-1. The molar absorptivity and sandell’s
sensitivity are calculated as 1.3342 X 104 L mol-1 cm-1 and 5.8 X 10-3 respectively. The proposed method has been succesfully applied for the determination of trace level of thorium in monazite sand.