ISO 13165-4:2025

This document specifies methods to determine 226Ra by alpha spectrometry in supply water, drinking water, rainwater, surface and ground water, marine water, as well as cooling water, industrial water, domestic, and industrial wastewater after proper sampling, handling and test sample preparation. The detection limit depends on the sample volume, the instrument used, the background count rate, the detection efficiency, the counting time and the chemical yield. The detection limit of the methods described in this document, using currently available alpha spectrometry apparatus, is equal to or lesser than 3 mBq·l−1 (or mBq·kg−1), which is lower than the WHO criteria for safe consumption of drinking water (1 Bq·l−1)[4]. This value can typically be achieved with a counting time of 48 h for a test sample volume of 40 ml. The method described in this document is applicable in the event of an emergency situation. Filtration of the test sample is necessary for the methods described in this document if suspended solids are present. The analysis of 226Ra adsorbed to suspended matter is not covered by this method, because it requires a mineralization step. In this case, the measurement is made on the different phases obtained. The final activity is the sum of all the measured activity concentrations. It is the user’s responsibility to ensure the validity of this test method for the water samples tested.