Method for determination of uranium isotopes in environmental samples by liquid-liquid extraction with triisooctylamine/xylene in hydrochloric media and alpha spectrometry

► The method allows determination of uranium isotopes in macro amounts of iron. ► The critical points in the method were studied in detail. ► An effective technique for total sample decomposition is the microwave acid digestion. ► Background concentrations of uranium isotopes in Bulgarian rivers are presented. ► Quality of the results was checked by analyzing various referent materials.