Performance of Accelerator Mass Spectrometry for ¹²⁹I using AgI-AgCl carrier-free coprecipitation

¹²⁹I has been successfully applied as tracer in environmental, geological, and oceanographic research. For samples with low stable iodine concentration and ultra low level ¹²⁹I, the sample preparation technique to separate iodine prior to AMS measurement has been a bottleneck, limiting the applicability of ¹²⁹I. We have reported a carrier-free method, using coprecipitation, to avoid the potential introduction of ¹²⁹I through the use of stable iodine carrier iodine. In this work, the detection limit and the analytical uncertainty of this method are investigated and minimum sample amount required to obtain reliable analytical results are estimated. The method is validated with a series of samples in ranges of known iodine concentrations and ¹²⁹I/¹²⁷I ratios. The results confirm our previous conclusion that an AMS target containing 5.0 μg iodine can be used for analyzing samples with ¹²⁹I/¹²⁷I > 10^-12, and that for samples with ¹²⁹I/¹²⁷I < 10^-13 more than 25 μg iodine is necessary.