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 ^239+240Pu and ²³⁸Pu 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 ^239+240Pu and 1.3 mBq kg^-1 for ²³⁸Pu 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 ^239+240Pu and from 0.0013 to 0.0158 Bq kg^-1 for ²³⁸Pu. (author)