Method development for the determination of 210Pb by liquid scintillation counting

Sammanfattning

Purpose: This thesis aimed to develop a method for the chemical separation of210Pb from water and solid samples to determine activity concentration using liquidscintillation counter (LSC).Method: A series of trials were made to establish a cost-effective method,including configuring the LSC (Hidex 300SL, Hidex Oy, Finland) for optimalperformance and to explore various chemical methods for the extraction and yielddetermination of 210Pb. The main LSC variables explored were different softwaresettings, scintillation vial materials and different scintillation cocktail with varyingvolume in relation to the sample. The chemical separation was evaluated by usinga solution with high concentration of interfering natural radionuclides, and wasvalidated by analyzing reference samples from IAEA proficiency tests. Once themethod was validated, seafood samples were analyzed to estimate the dose fromingestion of 210Pb. Yield determination was tested by gravimetry.Results: The method was able to remove most interfering radionuclides suchas Rn, U and Ra. The differences in vial material were small but choice ofscintillation cocktail was more prevalent. Especially the comparison of Goldstarand Prosafe Rn/AB. The applied method resulted in good agreement for bothwater and solid samples. The committed effective dose from 210Pb intake associatedwith consuming 5 kg of canned tuna over one year was estimated to be 27.6 ± 2.1μSv.Discussion and conclusion: A time and cost-effective method has been successfullydeveloped for the sample matrices fish and water. The method can detect activitiesof 210Pb in the scintillation vial as low as 0.2 Bq, and can concentrate and detect210Pb in water samples with activities concentrations as low as 0.8 Bq/kg formeasurement times of 450 minutes. The radiation dose from the analyzed seafoodwas relatively small compared to other contribution such as background radiation.However, 210Pb results in the in-growth of 210Po which has much higher doseimpact, and this radionuclide was not included in this preliminary estimation.Furthermore, the total preparation time is less than six hours for both water andfish samples where multiple samples can be prepared simultaneously.