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A fast and inexpensive sample preparation method for quantitative determination of radium in water involving α-liquid scintillation with α/β discrimination has been assessed. The optimal extraction of 226Ra by the extractive-scintillator cocktail RADAEX® requires pH above 10, which leads to salt precipitation in samples of high salinity. Salt precipitation can be prevented by addition of α-hydroxyisobutyric acid (HIBA). This methodology, including sample preparation and peak treatment, has been successfully tested with 13 natural and synthetic certified samples furnished by the International Atomic Energy Agency (IAEA). Furthermore, two natural waters collected in France during a Round Robin exercise have been used to evaluate the repeatability. For 5 ml sample aliquot and 240 000 s counting-time, the detection limit is estimated to be 0.04 Bq l−1. The sample preparation requires less than 1 h per sample. The precision ranges from about 50% at the detection limit to a maximal theoretical uncertainty of 4% due to the combined uncertainties of the pipettes, the balance and the chemical yield. The repeatability has been estimated to about 7%. |
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