This document specifies the determination of radium-226 (²²⁶Ra) activity concentration in non-saline water samples by extraction of its daughter radon-222 (²²²Rn) and its measurement using liquid scintillation analysis.

The test method described in this document, using currently available scintillation counters, has a detection limit of approximately 50 mBq·l⁻¹. This method is not applicable to the measurement of other radium isotopes.