The extraction of I-129 from solid matrices is a difficult task as pointed out by the report from inter-laboratory comparison. In this study we present results of I-129 extraction from solid matrices (soils and organic matters) through modification of a published procedure, which is now routinely used at our laboratory. The principle of the extraction is based on combustion of samples in a stream of oxygen at temperatures up to 800°C and trapping of the iodine in alkaline solution. Among the many extraction trials performed, we found that stepwise heating of the sample and continuous warming of the whole system were critical points to achieve high (>80%) extraction recovery. Temperature step rise was allocated to 300°C and 800°C at a total combustion time of about 2 hours/sample. To avoid condensation of iodine on the relatively cold surfaces at the metal connections, thermal ribbons were used to keep these parts of the system at a temperature of about 200°C. Sample size used for the extraction varies from 0.05 to 1g depending on the expected concentration of I-129. Carrier solution (containing 2 mg iodine) is added to sample and thoroughly mixed before combustion. Tests on carriers and blanks indicate experimental background (I-129/I-127) value at 10-13 whereas a lower value of 10-14 was obtained during measurement of natural AgI (iodargyrite). We have processed different types of natural samples (soils, tree leaves and fish tissues) and the results show excellent analytical reproducibility and agreement with expected reference values.
See more of Poster Session II
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)