ISO 13165-1:2013规定了通过提取子氡222（222Rn）测定非盐水样品中镭-226（226Ra）活度浓度，并使用液体闪烁计数进行测量。镭-226活度浓度可通过本试验方法使用当前可用的液体闪烁计数器进行测量，其降低至50 mBq l-1。此方法不适用于其它镭同位素的测定。

ISO 13165-1:2013 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 counting. Radium-226 activity concentrations which can be measured by this test method utilizing currently available liquid scintillation counters goes down to 50 mBq l−1. This method is not applicable to the measurement of other radium isotopes.