The aim of the experiment organized by the National Atomic Energy Agency of Poland, was to carry out an interlaboratory comparison on the determination of long-lived radium isotopes in waste waters from Polish coal mines. It was expected that the experiment would allow to evaluate the proficiency of the national participants, and to eliminate possible errors in their work.
9 participating laboratories have determined the concentrations of ²²⁶Ra and ²²⁸Ra (or only ²²⁶Ra) in 6 synthetic samples containing from 0 to 300 Bq dm^-3 of each isotope. The results have been evaluated according to recent recommendations of IUPAC, ISO and AOAC. It is concluded that a significant majority of the results meet the proficiency criterium at the selected target accuracy. In some cases small systematic errors appear. Only a few laboratories meet more rigorous proficiency criterium. Analytical methods used for radium determination have also been evaluated.