DETERMINATION OF IODINE WITH CHEMICAL FOR MS IN RAIN WATER BY FRACTIONAL SAMPLING NAA

A simple and rapid method has been developed for the fractional determ ination of particulate, iodide, iodate and non-ionic dissolved iodine in rain waters by using some filter technique and neutron activation a nalysis. The following procedure was chosen as a result of the tracer experiments. Particulate iodine in rain water (0.1 similar to 0.21) is obtained as the residue on Millipore HAWP filter paper by filtration and determined by INAA. Iodide and iodate ion in half of the filtrate are adsorbed on Expapier F3 anion exchange filter papers and passed th rough the filter as non-ionic dissolved iodine which is then sealed in to a plastic vial for irradiation. The iodate ion fraction is eluted w ith 15 ml of 0.5 M sodium hydroxide, and iodide ion and total ionic io dine (iodide+iodate) in another fraction are determined by the followi ng method. The irradiated sample is decomposed together with an iodide carrier solution containing I-131 by heating in a sodium hypochlorite solution. After decomposition, the solution is acidified with hydroch loric acid, and the insoluble residue is filtered off. To the filtrate sodium sulfite solution and palladium chloride solution are added, an d the precipitate of palladium iodide is separated with a glass fiber filter paper. Iodine contents of samples are calculated from the peak areas under the 443 keV gamma-ray of I-128 in the precipitate and comp arative standard. Corrections for chemical recovery are applied to the m by means of the areas under 365 keV gamma-ray of I-131. This method was applied to the rain water in Yokohama. The concentration of partic ulate, iodide, iodate and non-ionic dissolved iodine were 0.1 similar to 0.3, 1.0 similar to 3.7, 0.2 similar to 1.5 and 0 similar to 0.6 mu g/l. The recovery of iodine in this procedure was about 70%. About 30 min was required for the radiochemical procedure and the limit of det ermination was 1 ng/l of iodine in a volume of 0.21.