Determination of uranium by flow injection inductively coupled plasma mass spectrometry

A flow injection (FI) system for the on-line determination of uranium in environmental samples has been characterized and tested. The simple FI manifold uses off-the-shelf components to precisely manipulate the carrier, sample, eluent, and washing streams through a column separation module. The separation module preconcentrates the sample by a factor of 30 and removes the potentially interfering environmental matrix. TRUTM, a commercially available resin for extraction chromatography, is packed into a glass separation column (5 × 50 mm) in the limited dispersion (D = 2.8) FI system. Detection is performed by using inductively coupled plasma mass spectrometry (ICP-MS). Results are presented for the determination of 238U in groundwater samples. The total analysis time for each 5.0-ml aqueous sample is 6 min. The detection limit for 238U is 0.30 ng/l. By using certified groundwater samples, a precision of 1.1% (n = 4) and accuracy of ± 1.8% for 238U at 62.6 ng/l were observed. We also report the design and preliminary testing of a second FI-ICP-MS system that minimizes the influence of polyatomic ions (e.g., 238UH+) on the determination of minor actinides (e.g., 239Pu+) by ICP-MS.