E.1 DETERMINATION OF RADIOACTIVE IODINE IN WATER

E.1.1 Principle

Iodine is separated from the other radioactive species by extraction into carbon tetrachloride. Before this extraction is made, a complete interchange must be affected between the added iodine carrier and the tracer iodine present in the sample. The carrier iodide (I) is oxidized to periodate (IO4) in alkaline solution by NaOCl. The IO4 is reduced to I2 by hydroxylamine hydrochloride (NH2OH•HCl) and extracted into CCl4. The I2 is back-extracted by reduction to I with NaHSO3. Iodide is then precipitated as silver iodide for chemical yield measurement and radioactivity counting.

E.1.2 Reagents

CCl4 (Note 1)

Ethyl alcohol, 95%

HNO3, concentrated

Iodine carrier, 10.0 mg I/mL (Note 2)

NaOH, 5M

NaOCl, 5%

HN2OH HCl, 1M

NaHSO3, 0.5 M

AgNO3, 0.1 M

E.1.3 Procedure

  1. In a 250 mL separatory funnel containing 100 mL water sample (Note 3), add 2 mL of I carrier solution, 2 mL of NaOH, and 4 mL of NaOCl. Shake funnel for 2 minutes.

  2. Add 50 mL of CCl4, 4 mL of 1M NH2OH HCl and 3 mL of conc. HNO3.

  3. Shake the funnel for 2 minutes, and allow phases to separate.



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