Determination of traces of ²³⁷Np in environmental samples by ICP–MS after separation using TOA extraction chromatography

Abstract.

A simple, rapid, cost-efficient, and robust method for separation of ²³⁷Np with an extraction chromatographic column (TOA: tri-n-octylamine on Teflon powder) is outlined in detail and further improved for direct ICP–MS analysis. The column efficiently retained ²³⁷Np in 2 mol L^–1 HNO₃ medium and all of the ²³⁷Np was easily eluted with 0.02 mol L^–1 oxalic acid in 0.16 mol L^–1 HNO₃ at 95 °C. The separated solutions were free from most matrix elements and were aspirated into the ICP–MS directly. The decontamination factor for ²³⁸U is more than 10⁴. The instrumental detection limit for ²³⁷Np was 0.46 pg mL^–1, which corresponds to 1.2×10^–5 Bq mL^–1. The method is more rapid than traditional radiometric techniques. It is also considered to be more suitable for environmental monitoring than existing methods based on TOA.