Isotope dilution sector-field inductively coupled plasma mass spectrometry combined with extraction chromatography for rapid determination of 241Am in marine sediment samples:: A case study in Sagami Bay, Japan

(241)Am is a useful tracer for understanding biogeochemical processes in the marine environment. (241)Am also poses a potential radiation threat to human health due to the continuous increase of its concentration in the global environment. We report a rapid analytical method for determining (241)Am in marine sediments using isotope dilution sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) combined with a high-efficiency sample introduction system (APEX-Q). A selective CaF(2) co-precipitation procedure followed by TRU extraction chromatography was employed to effectively remove the major sediment matrix and to pre-concentrate (241)Am. We achieved an extremely low detection limit of 0.32 fg/g or 0.041 mBq/g (for I gram sediment), which is better than that of alpha spectrometry, and it allowed the accurate determination of (241)Am in low-level marine sediment samples. The accuracy and precision of the developed analytical method was evaluated using a laboratory prepared Am isotope standard solution and Ocean Sediment reference material (IAEA-368). The results were satisfactory. For sediment samples, overall chemical recoveries varied from 60-90%. The developed method was applied to the study of (241)Am depth distribution in Sagami Bay, Japan, where we observed different depth profiles between (241)Am activity and (239+240)Pu activity.