Ultratrace determination of uranium and plutonium by nano-volume flow injection double-focusing sector field inductively coupled plasma mass spectrometry (nFI–ICP-SFMS)

Abstract

A sensitive analytical procedure based on nano-volume flow injection (FI) and inductively coupled plasma double-focusing sector field mass spectrometry (ICP-SFMS) was developed for the ultratrace determination of uranium and plutonium. A 54-nl sample was injected by means of a nanovolume injector into a continuous flow of carrier liquid at 7 μl min⁻¹ prior to ICP-SFMS. The absolute detection limits were 9.1 × 10⁻¹⁷ g (3.8 × 10⁻¹⁹ mol, ∼230000 ²³⁸U atoms) and 1.5 × 10⁻¹⁷ g (6 × 10⁻²⁰ mol, ∼38000 ²⁴²Pu atoms) for uranium and plutonium, respectively. The method was validated for the determination of the uranium isotope ratios by the analysis of a certified isotope reference material (NIST U350). The analysis of a contaminated urine sample showed the enriched uranium to be the origin of contamination. Another application concerned the determination of plutonium at the subfemtomolar level in water with a detection limit down to the ag ml⁻¹ range (6 × 10⁻¹⁸ g ml⁻¹).