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.
CCl4 (Note 1)
Ethyl alcohol, 95%
Iodine carrier, 10.0 mg I−/mL (Note 2)
HN2OH HCl, 1M
NaHSO3, 0.5 M
AgNO3, 0.1 M
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.
Add 50 mL of CCl4, 4 mL of 1M NH2OH HCl and 3 mL of conc. HNO3.
Shake the funnel for 2 minutes, and allow phases to separate.