Determination of ²²⁶Ra at ultratrace level in mineral water samples by sector field inductively coupled plasma mass spectrometry

An analytical procedure has been proposed for the determination of ²²⁶Ra at the low femtogram per ml concentration level in mineral water samples using double focusing sector field TCP-MS (ICP-SFMS). For the pre-concentration and separation of radium from the matrix elements in water a tandem of a laboratory-prepared filter, based on MnO₂, and Eichrom "Sr-specific" resin was used. The recovery of the method was determined to be 70.5%. The limit of detection for ²²⁶Ra determination was 0.02 fg ml^-1, including a pre-concentration factor of 10. In addition, uranium concentration and uranium isotope ratios were measured by ICP-SFMS. In several mineral water samples with a relatively high uranium content, ²²⁶Ra concentrations were found between 0.7-15 fg ml^-1. The effective dose of the contribution was calculated using the radionuclide concentration and dose conversion factors from the World Health Organization, WHO (1993). Assuming a mineral water consumption of 2 1 d ^-1, a slightly higher calculated dose than the suggested limit for drinking water (0.1 mSv y^-1) was found in some samples.