Method for ²³⁶U Determination in Seawater Using Flow Injection Extraction Chromatography and Accelerator Mass Spectrometry

An automated analytical method implemented in a flow injection (FI) system was developed for rapid determination of ²³⁶U in 10 L seawater samples. ²³⁸U was used as a chemical yield tracer for the whole procedure, in which extraction chromatography (UTEVA) was exploited to purify uranium, after an effective iron hydroxide coprecipitation. Accelerator mass spectrometry (AMS) was applied for quantifying the ²³⁶U/²³⁸U ratio,and inductively coupled plasma mass spectrometry (ICPMS) was used to determine the absolute concentration of ²³⁸U; thus, the concentration of ²³⁶U can be calculated. The key experimental parameters affecting the analytical effectiveness were investigated and optimized in order to achieve high chemical yields and simple and rapid analysis as well as low procedure background. Besides, the operational conditions for the target preparation prior to the AMS measurement were optimized, on the basis of studying the coprecipitation behavior of uranium with iron hydroxide. The analytical results indicate that the developed method is simple and robust, providing satisfactory chemical yields (80−100%) and high analysis speed (4 h/sample), which could be an appealing alternative to conventional manual methods for ²³⁶U determination in its tracer application.