ISO 13163-2021 pdf download.Water quality- Lead-210- Test method using liquid scintillation counting.
4 Principle
Lead-210 is a naturally occurring beta-emitting radionuclide with a maximum beta-energy of 63,5(5) keV and a half-life of 22,23(12) years W1191. It appears in the 23HjJ decay series (4n+2) as along- lived decay product of 222Rn (see Figure 1).
This document describes the measurement of 210Pb after separation from its progeny, 210Bi and 210Po and its activity is measured by liquid scintillation counting, either immediately after its separation or indirectly after ingrowth of its progeny 210Bi l1lll to[341
Lead-210 is chemically purified from potential interferents, which consist of any isotope that can make the liquid scintillator emits light in the region of interest (ROl) of 210Pb. Different methods for the purification of 210Pb are presented in Annex A.
After removal of the potential interferents, the chemical recovery of lead (Re) is determined. The purified sample is mixed with the scintillation cocktail in a counting vial to obtain a homogenous medium. The vial is counted by LSC.
Because of their identical separation behaviour in the extraction chromatographic procedure and their half-lives, 214Pb, 211Pb, and 212Pb are potential interferences (Table 1).
To avoid the possible interferences of the isotopes with short half-lives such as 211Pb and 214Pb and their progeny during the liquid scintillation counting, it Is recommended to wait at least 3 h between elution of lead and sample counting to allow these radionuclides to substantially decay.
The beta-energies of 2t1Pb, 212Pb and 214Pb and their progeny are higher than the maximum energy of 210Pb. The 3 h delay time before counting can be reduced by setting appropriate counting windows different from the one set for 210Pb to eliminate these interferences. In this approach, it is possible to start counting without a 3 h delay to neglect 210Bi ingrowth during counting.
It is necessary to know the content of stable lead in the sample in order to adjust the quantity of the lead carrier to add to avoid resin saturation and to allow for the chemical recovery of 210Pb. Total content of stable lead in samples should not exceed 10 mg Pb per gram of extraction chromatographic resin 18C6 to be used for the lead separation.
For samples with high stable lead content and/or high activity concentration, dilution of the sample is required to avoid either resin or detector saturation during the separation and counting steps, respectively.ISO 13163 pdf download.