土壤样品中超痕量^129I的无载体共沉淀分离及加速器质谱测定

Determination of Low Level ^(129)I in Soil Samples Using Coprecipitation Separation of Carrier Free Iodine and Accelerator Mass Spectrometric Measurement

环境样品中超微量129I的准确测定是天然129I地质定年和环境示踪应用的关键。本研究通过高温热解法分离土壤中的碘,并将其收集于碱性捕集液中,再利用AgI-AgCl共沉淀方法实现捕集液中碘的无载体分离;采用3 MV加速器质谱仪测量沉淀样品中129I/127I比值。通过优化分离和分析条件,高温热解过程中碘的分离效率达95%以上;无载体共沉淀过程碘的回收率为75%～85%;样品中碘的总分离效率大于70%。应用本方法对低碘含量土壤样品中129I/127I原子比值低至10-11的超微量129I进行了准确测定。结果表明:本方法适用于129I/127I比值低至10-12的同类样品的分析。

The accurate determination of ultra low level ^129I in sample is critical and essential for the application of natural ^129I in geological dating and environmental tracer studies.In this work,iodine was first separated from soil by combustion at high temperature;the released iodine was collected in an alkali trap solution.AgI-AgCl coprecipitaiton was used to separate carrier free iodine from the trap solution and to prepare target.^129I in the target was then measured using a 3.0 MV accelerator mass spectrometer.The recovery of iodine during the combustion is higher than 95%.An iodine recovery of about 75%-85% was obtained in the coprecipitation and the total recovery of iodine is above 70%.The developed method has been successfully used to determine 129I in soil sample with low iodine content.A ^129I/^127I atomic ratio as low as 10^-11 in the deep soil has been determined.The determination of ^129I/^127I was ratio down to 10^-12 in solid samples.