Application of polyethylene glycol 2000 to remove silica in the determination of 239+240Pu and 238Pu in soil samples by alpha-spectrometry

A new method was developed for determination of Pu239+240 and Pu-238 in environmental soil samples by a Microthene-TOA column and alpha-spectrometry. The improvement of the method was based on the new findings: (1) leaching efficiency comparison between fusion technique and direct HNO3 leaching, and (2) removal effect of silicates from soil leaching solution with PEG. The method was checked by analysing a certified reference material, showing good agreement with the recommended values. The detection limit was 2.1 mBq kg(-1) for Pu239+240 and 1.3 mBq kg(-1) for Pu-238 when 20 g soil was analysed. Fifteen soil samples collected in Italy were analysed, and the obtained Pu yield was 79.5 +/- 11.1%, being high and stable. The activity concentrations in the soil samples ranged from 0.034 to 0.447 Bq kg(-1) for Pu239+240 and from 0.0013 to 0.0158 Bq kg(-1) for Pu-238.

Automated summary

A new method was developed for the determination of Pu239+240 and Pu-238 in environmental soil samples using a Microthene-TOA column and alpha-spectrometry. The method was improved based on the comparison of leaching efficiency between fusion technique and direct HNO3 leaching and the removal effect of silicates from soil leaching solution with PEG. The method was validated using a certified reference material and showed good agreement with the recommended values. The detection limits for Pu239+240 and Pu-238 were 2.1 mBq kg(-1) and 1.3 mBq kg(-1) respectively when analyzing 20 g soil.