EXTRACTION SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF URANIUM IN GEOLOGICAL SAMPLES USING A TERNARY COMPLEX OF 2-(PARA-METHYLPHENYLAZO)PYRIDINE AND THIOCYANATE

An uranyl ion (UO2(2+)) reacts with 2-(p-methylphenylazo)pyridine in thiocyanate system. The species is extractable quantitatively into methyl isobutyl ketone (MIBK) in the presence of nitrate ion, showing an absorption maximum at 370 nm. Beer's law is obeyed over the range 0.15 - 1.5-mu-g of uranium/ml. The molar absorptivity and Sandell's sensitivity are 0.166 x 10(4) l mol-1 cm-1 (on the basis of uranium content) and 0.0014-mu-g/cm2, respectively. Various international geochemical reference samples were chosen to check the validity of the method. The results obtained were in good agreement with the published data.