ASTM D4785-20

5.1 This test method was developed for measuring low levels of radioactive iodine in water. The results of the test may be used to determine if the concentration of several radioisotopes of iodine in the sample exceeds the regulatory limits for drinking water. With suitable counting techniques, sample size, and counting time, a detection limit of less than 0.037 Bq/L (1 pCi/L) is attainable by gamma-ray spectrometry.

5.2 This test method is intended for the analysis of iodine radioisotopes with half-lives greater than 2 hours, which include ¹²¹I, ¹²³I, ¹²⁴I, ¹²⁵I, ¹²⁶I, ¹²⁹I, ¹³⁰I, ¹³¹I, ¹³²I, ¹³³I, and ¹³⁵I. The test method was tested according to Practice D2777 using only ¹³¹I. The user of this test method is responsible for determining applicability, bias, and precision for the measurement of other iodine radioisotopes.

1.1 This test method covers the quantification of low levels of radioactive iodine in water by means of chemical separation and counting with a high-resolution gamma ray detector. Iodine is chemically separated from a 4 L water sample using ion exchange and solvent extraction and is then precipitated as cuprous iodide for counting.

1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.