PROCEDURES FOR THE DETERMINATION OF IODINE BY NEUTRON ACTIVATION

The great bulk of the work which has been done on neutron activation anal-ysis for iodine has dealt with natural iodine-127 ( I(n,Y) I), and the procedures described below are concerned primarily with that isotope. Because of the growing interest in the long-lived, fission-produced iodine-129 (1.57 x 10 y), the section is concluded with a method for the sequential analysis of low levels of iodine-131, iodine-129, and natural iodine in environmental samples based on chemical separation and neutron activation analysis techniques. 

Aqueous ammonia was added to the water sample prior to neutron irradiation. 

Following irradiation, the indicated reagents were added to the sample sodium 

The solution was then passed through a Dowex 1-XlO resin column on which molecular Ig had been irreversibly fixed. (The resin was prepared by converting the resin originally in the hydroxide form to the iodide and oxidizing the latter to the free element by means of sodium nitrite in acidic solution. The iodinated resin was preconditioned with aqueous sodium nitrate.) Iodine-128 was counted directly on the resin bed. Calibrated potassium iodide standards were also counted. The limit of sensitivity of the method was determined to be 3.5 x 10 pg of iodine and recoveries of iodine were 95-100%. 

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