DETERMINATION OF THORIUM AND URANIUM IN NITROPHOSPHATE FERTILIZER SOLUTION BY ION CHROMATOGRAPHY

Different phosphate rocks contain various concentrations of thorium and uranium and the range of these concentrations can be significant. Digestion of phosphate rocks with concentrated nitric acid in a fertilizer production process leads to the dissolution of these metals in the resulting nitrophosphate solution. A direct method with a total analysis time of 10 min is described for the determination of thorium and uranium in nitrophosphate fertilizer solution. The method is based on cation-exchange chromatography coupled with spectrophotometric postcolumn detection with Arsenate III at 660 nm. Elution is performed with a gradient concentration of hydrochloric acid or nitric acid and ammonium sulphate, utilizing a strong cation-exchange analytical column to perform the separation.