In vitro monitoring of natural thorium in urine using fluorimeter

► Thorium is quantitatively extracted from pH 2.5-3.5 HCl into 0.01 M PC88A/toluene. ► High tolerance ratios were found for the presence of Ca & Mg in the aqueous phase. ► In acetonitrile solvent,fluoresence intensity due to Th-3-hydroxy flavones complex is found to be linear in the range 0.1-5.0 μg/ml. ► This method is applicable for dose assessment of occupational workers who handle natural thorium.