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Semi-automated procedure for the determination of 89, 90Sr in environmental samples by Cherenkov counting

Development of new chromatographic resins in the last two decades Sr resin, AnaLig-01 and SuperLig 620 has significantly simplified separation of strontium from various types of samples. These resins, that have principles based on molecular recognition, are highly selective for strontium binding. In combination with appropriate detection methods they enable automatic determination of radioactive strontium. Sequential injection analysis and equilibration based sensor column analysis were developed for the determination of long lived 90Sr (28.8 y) in liquid radioactive waste and water samples.1-3 However, 89Sr that has short half-life (50.5 d), can also be present in samples, especially in those exposed to fresh fallout from nuclear reactor. Classical analysis of 89Sr requires isolation of 90Y, usually after attaining of secular equilibrium of 90Sr-90Y and the whole procedure takes at least 16 days. However, by using Cherenkov counting technique, determination time may be significantly reduced. Unlike 90Sr that emits low energy electrons, its daughter 90Y as well as 89Sr, generates Cherenkov photons in aqueous media. Consequently, by successive counting within 64 hours, 89Sr and 90Sr via 90Y can be determined. Therefore, the main aim of this research is development of semi-automated procedure for the determination of 89, 90Sr. It includes solid phase extraction (SPE) of strontium from liquid samples and Cherenkov counting of its isotopes. The procedure is based on sample - column equilibration and off- line detection of bound 89, 90Sr on the column. Sample is pumped through column at constant flow rate until the breakthrough or saturation point is achieved. The 89, 90Sr is determined by counting on column in PE vial. It will be shown how strontium can be selectively bound on the Sr resin, AnaLig-01 and SuperLig 620 resins and separated from interfering radionuclides. Also, influence of column geometry, amount of resin and media in PE vial around the column on quantity determination, detection efficiency and achievable lower detection limits will be discussed. The method is tested in proficiency testing samples and natural water samples.

Semi-automated procedure; solid phase extraction; Cherenkov counting; 89; 90Sr determination

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