Electrochemically modulated separations for rapid and sensitive isotopic analysis
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Electrochemically modulated separations for rapid and sensitive isotopic analysis Martin Liezers • Sandra H. Pratt • Garret L. Hart Douglas C. Duckworth
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Received: 25 July 2012 / Published online: 24 August 2012 Ó Akade´miai Kiado´, Budapest, Hungary 2012
Abstract The desire for more rapid and sensitive analytical determinations of actinides in the environment is being addressed in our laboratory through the development of electrochemically modulated separations (EMS) coupled to multiple ion counting inductively coupled plasma mass spectrometry (MIC-ICP-MS). This work is focused on the characterization of EMS separations of U and Pu in swipe materials. EMS provides electrochemically controlled surface complexation of either U(IV) or Pu(IV), depending on the potential applied to an anodized glassy carbon electrode. The accumulation and rinse yields *90 % recovery efficiency, matrix elimination, and analyte concentration of the selected actinide. All this is performed solely under the control of the applied potential. Once isolated, the concentrated actinide is released into a *1 lL volume of dilute (0.5 M) HNO3, resulting in a volumetrically concentrated transient signal that is ideal for multiple ion counting detection. Coupled with a Thermo Fisher Scientific Neptune Plus MIC-ICP-MS, atom utilization efficiencies are normally 1 %, comparable to the gold standard thermal ionization mass spectrometry (TIMS), but only requiring 20 min for separation and analysis; whereas TIMS requires [50 h for off-line separation, filament
M. Liezers (&) S. H. Pratt G. L. Hart D. C. Duckworth Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, Richland, WA 99352, USA e-mail: [email protected] S. H. Pratt e-mail: [email protected] G. L. Hart e-mail: [email protected] D. C. Duckworth e-mail: [email protected]
preparation, and isotopic analysis. Method and analytical figures of merit will be highlighted. Keywords Uranium Plutonium Isotope ratio Multi-collector ICP-MS Electrochemistry Pre-concentration Separations Matrix elimination Glassy carbon
Introduction Dust swipes taken from in or around nuclear facilities form a relatively non-invasive and widely accepted sampling method used to verify compliance with international treaty obligations aimed at limiting nuclear weapons proliferation [1–3]. The total amount of material collected by this procedure can be very small (mg), depending on the sampling location, where the actinide component forms only a very small sub-fraction of the dust sample. The cotton swipe material itself contains low nanogram levels of natural uranium contamination, while the weight of plutonium collected may only be at femtogram or lower levels. As a result this form of actinide sample analysis can be quite challenging, especially for plutonium. The classical method routinely adopted has been chromatographic column separations using ion exchange resins [4] to produce isolated U and Pu fractions for either TIMS or ICP-MS analysis. While colum
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