Ion chromatography and liquid scintillation counting coupled to determine α- and β-emitters

We present a rapid procedure for separation and measurement of α- and β-emitters in environmental water samples. The method makes use of ion-chromatographic (IC) separation and enrichment on cationic columns, followed by detection with a liquid scintillation counter (LSC). Retention times and their dependencies from HCl eluent concentration on a DIONEX Ion Pac CS 12 column are presented for Po, Sr and Ra. Radium as a heavy earth alkaline element is eluted from the column with the highest retention times: with 20 mMol HCl as an eluent, it is separated from the majority of interfering natural radionuclides and fission products. The fractions are collected and measured with a liquid scintillation spectrometer. The general procedure without enrichment and measurement is done in less than 1 h. For α-emitters, the background has been reduced to 0.1 counts/min by applying electronic α/β-discrimination or more preferably using solid scintillator caps. They shift the spectrum of α-emitters to higher energies and allow their separation from β-emitters even in an activity ratio of α(210Po): β(90Sr/90Y) of 1:1000. If a 1 liter water sample is enriched on a pair of guard columns, a sensitivity down to 10−3 Bq/l per radionuclide is obtainable. The arrangement of guard columns and the saturation studies are reported. The saturation behaviour for different cations has been examined.