ISO 4685:2024

This document specifies methods to determine 226Ra concentration by inductively coupled plasma mass spectrometry (ICP-MS). The mass concentrations obtained can be converted into activity concentrations. The method is applicable to test samples of drinking water, rainwater, surface and ground water, after proper sampling and 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 method described in this document, using currently available equipment, is approximately 10 mBq·l-1, which is better than the WHO criteria for safe consumption of drinking water (1 Bq·l-1). This method covers the measurement of 226Ra in water at activity concentrations between 0,001 Bq·l−1 and 100 Bq·l−1. Samples with concentrations higher than 1 Bq·l−1 can be measured if a dilution is performed. The method described in this document is applicable in the event of an emergency situation. In this method, filtration of the test sample is necessary. The analysis of 226Ra adsorbed to suspended matter is not covered by this method. The analysis of the insoluble fraction requires a mineralization step that is not covered by this document. In this case, the measurement is made on the different phases obtained. It is the user’s responsibility to ensure the validity of this test method for the water samples tested.