Method for Ultratrace Level (241)Am Determination in Large Soil Samples by Sector Field-Inductively Coupled Plasma Mass Spectrometry: With Emphasis on the Removal of Spectral Interferences and Matrix Effect.

Abstract

A new method using sector field-inductively coupled plasma mass spectrometry (SF-ICPMS) was developed for the determination of (241)Am in large soil samples to provide realistic soil-plant transfer parameter data for dose assessment of nuclear waste disposal plans. We investigated four subjects: extraction behaviors of interfering elements (Bi, Tl, Hg, Pb, Hf, and Pt) on DGA resin (normal type, abbreviated as DGA-N); soil matrix element removal (Mg, Fe, Al, K, Na) using Fe(OH)3, CaF2, and CaC2O4 coprecipitations; Am and rare earth elements (REEs) separation on DGA-N and TEVA resins; and optimization of SF-ICPMS (equipped with a high efficiency nebulizer (HEN)) for Am determination. Our method utilized concentrated HNO3 to leach Am from 2 to 20 g soil samples. The CaC2O4 coprecipitation was used to remove major metals in soil and followed by Am/interfering elements separation using the proposed UTEVA + DGA-N procedure. After a further separation of REEs on TEVA resin, (241)Am was determined by HEN-SF-ICPMS. This method eliminated the matrix effect in ICPMS (241)Am measurement for large soil samples. The high decontamination factors (DFs) of interfering elements enable their thorough removal, and in particular, the DF of Pu (7 × 10(5)) was the highest ever reported in (241)Am studies; thus, this method is capable of analyzing (241)Pu-contaminated Fukushima Daiichi Nuclear Power Plant (FDNPP) sourced soil samples. A low detection limit of 0.012 mBq g(-1) for (241)Am was achieved. The chemical recovery of Am (76-82%) was stable for soil samples. This method can be employed for the low level (241)Am determination in large size soil samples that are contaminated with (241)Pu.