Evaluation of different LSC methods for 222Rn determination in waters

Jovana Nikolov; Ivana Stojković; Nataša Todorović; Branislava Tenjović; Srđan Vuković; Jovana Knežević

doi:10.1016/j.apradiso.2018.09.013

Evaluation of different LSC methods for ²²²Rn determination in waters

Appl Radiat Isot. 2018 Dec:142:56-63. doi: 10.1016/j.apradiso.2018.09.013. Epub 2018 Sep 13.

Authors

Jovana Nikolov¹, Ivana Stojković², Nataša Todorović³, Branislava Tenjović⁴, Srđan Vuković³, Jovana Knežević³

Affiliations

¹ University of Novi Sad, Faculty of Sciences, Department of Physics, Novi Sad, Serbia. Electronic address: jovana.nikolov@df.uns.ac.rs.
² University of Novi Sad, Faculty of Technical Science, Novi Sad, Serbia.
³ University of Novi Sad, Faculty of Sciences, Department of Physics, Novi Sad, Serbia.
⁴ University of Novi Sad, Faculty of Sciences, Department of Chemistry, Novi Sad, Serbia.

PMID: 30248591
DOI: 10.1016/j.apradiso.2018.09.013

Abstract

Monitoring of ²²²Rn in drinking or surface waters, as well as in groundwater has been performed regularly in connection with geological, hydrogeological and hydrological surveys and health hazard studies. Liquid scintillation counting (LSC) is often preferred analytical method for ²²²Rn measurements in waters as it allows multiple-sample automatic analysis. LSC method implies mixing of water samples with organic scintillation cocktail, which triggers radon diffusion from the aqueous into an organic phase for which it has a much greater affinity, eliminating the possibility of radon emanation in that manner. The main aim of this paper is calibration of the liquid scintillation counter Qunatulus 1220™ for measuring of radon in water and evaluation of two different methods (one-phase and two-phase) in order to obtain the most suitable LSC technique for radon in water measurement. In this study four different scintillation cocktails were tested: one miscible (Ultima Gold AB) and three immiscible (High Efficiency Mineral Oil Scintillator, Opti-Fluor O and Ultima Gold F). Evaluation of presented methods was based on obtained detection efficiency and achieved Minimal Detectable Activity (MDA) values. Comparison of presented methods, accuracy and precision, as well as different scintillation cocktail's performance, was considered from results of measurements of ²²⁶Ra spiked water samples with known activity and environmental samples. LSC results were compared with the results of radon in water measurement obtained by alpha spectrometer RAD7. Calibration was done as a dependence of calibration factor (CF) from Pulse Shape Analysis (PSA). According to the obtained results, with proper adjustment of calibration parameters, both methods could be used for radon in water measurements. The obtained MDA values for all four scintillation cocktails are very low, less than 0.1 Bq l^-1 for measuring time of 300 min.

Keywords: PSA discriminator; Radon in water measurement; The calibration factor; Water-immiscible LS cocktails; Water-miscible LS cocktail.