Determination of neptunium in a reprocessing plant by an on-line solid-phase extraction/electrochemical detection system

Taguchi, Shigeo ; Yamamoto, Masahiko   ; Surugaya, Naoki 

A flow-based electrochemical detection system coupled to a solid-phase extraction column was developed for the determination of neptunium. A Np(V) was oxidized completely to Np(VI) by electrolysis using a column electrode composed of carbon fibers. The effluent was loaded onto a TEVA column, and then onto UTEVA column with 3 mol L HNO. The Np(VI) was eluted with 0.01 mol L HNO, and then introduced directly into a flow-through electrolysis cell. An electrochemical detection with a working potential of +0.1 V (vs. Ag/AgCl) was used to detect Np(VI). The current produced on reduction of Np(VI) was monitored continuously, and the Np(VI) concentration was calculated from the peak area. The relative standard deviation of ten analyses was 2.4 % for a Np(VI) solution (0.50 mg L) containing 1.0 g of Np. The detection limit calculated from three-times the standard deviation was 35 g L (70 ng Np).