Feasibility of isotope dilution calibration for the determination of thallium in sediment using slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry |
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| Institution: | 1. CEA, DEN, DPC, SECR, Laboratoire d''Etude du Comportement des Bétons et des Argiles, F-91191 Gif-sur-Yvette, France;2. Paris Est University, Navier Institute (UMR8205 CNRS/ENPC/IFSTTAR), 2 allée Kepler, F-77420 Marne La Vallée, France;1. Dep. of Mechanical and Mining Engineering, Escuela Politécnica Superior de Jaén, University of Jaén, Campus Las Lagunillas s/n, 23071 Jaén, Spain;2. Dep. of Electronic Engineering and Automatics, Escuela Politécnica Superior de Jaén, University of Jaén, Campus Las Lagunillas s/n, 23071 Jaén, Spain;1. Laboratory for Environmental Chemistry and Bioanalytics, Institute of Chemistry, ELTE - Eötvös Loránd University, H-1117 Budapest, Pázmány Péter stny. 1/A, Hungary;2. Hungarian Satellite Centre to Trace Elements Institute for UNESCO, Institute of Chemistry, ELTE - Eötvös Loránd University, H-1117 Budapest, Pázmány Péter stny. 1/A, Hungary;3. MTA Centre for Ecological Research, Danube Research Institute, H-1113 Budapest, Karolina út 29, Hungary |
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| Abstract: | Isotope dilution (ID) calibration was investigated as a means to establish accurate values for thallium in a variety of sediment reference materials using slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) as the analytical tool. The pyrolysis curve, as well as the analysis of SRM 2704 Buffalo River Sediment, suggested that a pyrolysis temperature of 700°C could be used for this determination. The analytical results for a number of river sediment reference materials confirmed this finding; however, the results for marine sediments were far too high, indicating a serious problem with these samples. Careful investigation revealed the following interference mechanism as the most likely one. The chloride content of marine sediments is some two orders of magnitude higher than that of river sediments, and the chloride leaches out very easily into the aqueous phase of the slurry. The thallium that is in solution forms TlCl upon drying, which is easily volatilized and lost at pyrolysis temperatures >400°C. As the enriched isotope spike was added in solution, and the ‘original’ thallium is retained, at least in part, in the sediment particles, the spiked thallium is preferentially lost, leading to the excessively high analytical results. Accurate results for Tl in marine and river sediments could be obtained using pyrolysis temperatures of 400 and ≤700°C, respectively. The detection limit calculated from 3×S.D. (n=5) of the sediment with the lowest thallium content (HISS-1) was found to be 0.003 μg g−1. The precision at the 0.5–1.0-μg g−1 Tl level based on five consecutive readings was 1.3–4.0% R.S.D. |
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