Determination of 129I in seawater and some environmental materials by neutron activation analysis

A neutron activation analysis method with pre-irradiation separation and post-irradiation purification is presented for the determination of I-129 content and I-129/I-127 ratio in some environmental samples, such as seawater, seaweed, grass and soil. An evaporation concentration followed by solvent extraction was used for the separation of iodine from seawater, and alkaline ashing or alkaline fusion followed by water leaching and solvent extraction for vegetation and soil samples. A further post-irradiation purification of iodine was carried out by extraction and PdI2 precipitation. The concentrations of I-129 and I-127 were then measured by counting I-130 and I-126, respectively. The recoveries of iodine reach 60-95% and more than 98% in pre-concentration and post-irradiation purification procedures, respectively, The detection limit of this method for I-129 reached 2-3 x 10(-13) g. Some samples collected in Denmark and Iceland were analysed.