Abstract
Considering increasing importance of analyzing seawater for 129I, we developed a practical method for determination of 129I in seawater using accelerator mass spectrometry by pre-treatment with solvent extraction. In this method, total inorganic iodine in 1 liter of seawater is extracted by hexane after iodate ions were reduced to iodide ions by ascorbic acid and iodide ions were oxidized by sodium nitrite. Recovery of total iodine was determined by ion chromatography. Accuracy and precision were examined by analyzing seawater samples of known concentrations and seawater added with the diluted NIST SRM 3230 Level I solutions. Repeatability of AMS measurement was checked using the seawater sample and AgI prepared from AgNO3 and KI. As a result of analyzing seawater samples of known concentrations, accuracy and precision were found to be quite satisfactory. Overall repeatability of the analysis by the present method including pre-treatment was approximately 10% (R.S.D.) . It was concluded that 129I concentration levels from 106 to 107 atoms L-1 or over in seawater can be determined by this method with sufficient accuracy and precision.
