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

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.