Analytica Chimica Acta 532 (2005) 47–54 Uranium emission spectra with a low power microwave plasma source Yixiang Duan a,∗ , Susan T. Scherrer b , Sudip P. Koirala b , Chuji Wang b , Christopher B. Winstead c a C-ACS, MS K484, Los Alamos National Laboratory, Chemical Science and Technology Division, Los Alamos, NM 87545, USA b Diagnostic Instrumentation & Analysis Laboratory, Mississippi State University, Starkville, MS 39759, USA c Department of Physics and Astronomy, University of Southern Mississippi, USM Box 5046, Hattiesburg, MS 39406, USA Received 21 August 2004; received in revised form 18 October 2004; accepted 18 October 2004 Available online 28 December 2004 Abstract This work presents the first report of uranium spectra generated by a low power microwave plasma source to conduct emission measurements. Distinct uranium peaks in the wavelength range examined from 320 to 430 nm have been successfully obtained with a 200 W plasma utilizing low gas flow rates. The influence of temperature on the uranium behavior in the plasma source is discussed, and the intensity of the spectral lines obtained with this low power source is systematically compared with the results reported in literature, in which high power plasma sources were employed. Concentration effects are studied and the calibration curves are made for some strong spectral lines. The detection limits of uranium are also estimated to be at the 0.4 ppm level, with linear dynamic range at least two and half orders of magnitude. This research establishes a method to effectively generate uranium atoms and ions at a low power and low gas flow rate, which should be useful for uranium fundamental characteristic studies and on-site uranium monitoring work. © 2004 Elsevier B.V. All rights reserved. Keywords: Microwave plasma; Emission spectrometry; Uranium; Spectral line; Measurement 1. Introduction Uranium, which is particularly important in nuclear pro- duction facilities, is one of the most important elements in the periodic table. Due to the complexity of the atomic structure and the abundance of energy levels, uranium, a member of the actinide family, presents a special challenge in spectral studies. It is estimated that there are over 300,000 spectral lines for uranium atoms (U I) and uranium ions (U II) alone [1,2]. Additionally, the particular chemical and physical prop- erties of uranium make this element hard to handle in flames or plasma sources. Chemically, uranium can be easily com- bined with active species during the atomization process to form oxides at atmospheric pressure in hot sources and to ∗ Corresponding author. Tel.: +1 505 665 9219; fax: +1 505 665 5982. E-mail address: yduan@lanl.gov (Y. Duan). form carbides in graphite furnace [3]. Physically, uranium has a relatively low ionization potential (∼6.08 eV), which results in almost complete ionization when it is introduced into a high power plasma source, such as an inductively cou- pled plasma (ICP) [4]. These chemical and physical features yield a poor atomization efficiency for uranium in high tem- perature plasma sources. Furthermore, low energy sources, such as flames or graphite furnaces cannot efficiently atomize uranium [5], thus preventing uranium detection to any useful degree by any flame or furnace with either atomic emission or absorption methods. With the most sensitive ion emission line, 385.957 nm, Winge et al. reported a detection limit of 250 ng/ml uranium in the early comprehensive studies of ICP emission spectrometry [6], and this detection limit was subse- quently improved (16 ng/ml) by Boumans and Vrakking [7]. We have been working for years to design and develop new plasma sources for atomic emission and absorption measure- 0003-2670/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2004.10.076