In vitro monitoring of natural thorium in urine using fluorimeter

A relatively less expensive and less time consuming radio analytical technique for quantitative determination of Thnat in urine at mBq level is developed and reported in this paper. Th in urine is co-precipitated with Ca3(PO4)2 from wet oxidized urine matrix and the precipitate is dissolved in HNO3 and evaporated to dryness. The residue is dissolved in 3 M HCl and 200 mg of Na-EDTA is added to mask Ca2+, Mg2+ and Fe3+ ions. Th4+ is extracted into 0.01 M PC-88A (2-ethyl hexyl phosphonic acid mono-2-ethylhexyl ester), dissolved in toluene from the experimentally optimized pH 2.5 ± 0.3 in aqueous phase. Th4+ is stripped into 8.0 M HCl and evaporated to dryness. The content of the beaker is dissolved in pH 1.8 HCl and complexed with 3-hydroxy flavone. The sample is excited at 397 nm and fluorescence intensity is measured at 462 nm. The detailed study of the method is presented in this paper. Interference study on elements that are normally present in urine and other actinides (if present) is also given.