An analytical method for thorium in various aqueous samples such as urine, tap water and sea water is described.
The method proposed is as follows: thorium is co-precipitated with the basic phosphate precipitates of calcium and magnesium in a sample of a large volume. The precipitate is dissolved with 1 N nitric acid and then the solution is made 40 v/o 1 N nitric acid-60 v/o ethanol mixed solution by adding ethanol. The resultant solution is passed through the Dowex 1-X8 resin column (0.7cm²×2.8cm), and the column is washed with 20 v/o 1 N nitric acid- 80 v/o ethanol mixed solution and then water. The elution is carried out with 8N hydrochloric acid. The amount of thorium is determined by a photoelectric spectrometer, using neo-thorin.
The sensitivity is 0.51.0 μg Th, and recovery for μg amount of thorium is 99% for 400600 ml of human urine, 97% or 96% for 1, 000 ml of tap water or sea water, respectively.