Determination of Actinide Elements in Environmental Samples by Icp-ms

DETERMINATION OF ACTINDE ELEMENTS iN ENVIRONMENTAL SAMPLES BY ICP-MS Jason Bedford Truscott Methods for the determination of the actinide elements m water, biological, soil and sediment samples have been developed usmg on-line sohd phase extraction and high performance liquid chromatography (I{PLC) coupled with mductively coupled plasma mass spectrometry (ICP-MS) Initial applications utilised a commercially available resm, namely TRU-Spec resin, for efficient removal of the matrix pnor to elution of uranium and thorium analytes Comparative analyses of reference matenals and natural water samples from Plymouth and Dartmoor demonstrated significant improvement m precision and speed of analysis by using TRU-Spec coupled to ICPMS compared with alpha spectrometry. Further applications of the TRU-Spec resin for the determination of the transuranic actinide elements neptunium, plutonium and americium, resulted m the successful determination of Pu and 7Np in biological reference matenals Detection limits were 700, 850, and 600 attograms (ag) for 7Np, Pu, and 241Am, respectively, for a 0 5 ml sample injection, and better than 200 ag g 4 with 50 ml pre-concentration when sector field (SF) ICP-MS was used A method for the selective sequential elution of uranium and plutonium was also developed to facilitate the determination of Pu without interference due to the 8U'H polyatomic ion, caused by high concentrations of 8U in sediment samples Investigations were performed into the use of a polymeric substrate, which was dynamically coated with chelating dyes such as xylenol orange and 4-(2-pyndylazo) resorcmol, and a silica substrate coated with permanently bonded iminodiacetic acid The latter was used for the successful determination of uranium and thorium in certified reference matenal waters However, the column was found to have a high affinity for iron, makIng it unsuitable for the determination of the actinides in soil and sediment samples Subsequently, a polystyrene substrate which was dynamically coated with dipicolmic acid was used for HPLC coupled with SF-ICP-MS Using this column it was possible to separate the various actinides from each other and from the matnx In particular, it was possible to separate plutonium and uranium to facilitate interference-free determination of the former. The column also exhibited some selectivity for different oxidation states of Np, Pu and U Two oxidation states each for plutonium and neptunium were found, tentatively identified as Np(V) and Pu(ffl) elutmg at the solvent front, and Np(IV) and Pu(IV) eluting much later Detection limits were 12, 8, and 4 fg for 7Np, Pu, and 241Am, respectively, for a 0 5 ml injection, and the system was successfully used for the determination of Pu in water, biological and soil reference materials