Microwave-assisted pre-treatment of environmental samples for the determination of 90Sr Original Research Article

In this paper microwave-assisted pre-treatments for the determination of 90Sr in environmental samples are presented. Six matrices were studied: organic and mineral soils, sediment, grass, and ashes from grass and milk matrices. Total attack – using HNO3, HClO4, HF and H2O2 – and leaching digestion methods, which avoided the use of HF, were optimised for each matrix. Since no statistically significant differences were found between the results obtained using the two procedures, leaching digestion was preferred, as long as the digestion time and the number and amount of reagent were lower. The influence of sample intake on 90Sr activity concentration determination was studied and no significant influence was observed. Total time of attack varied from 75 min for organic soils to 95 min for mineral soils and sediment for complete dissolution procedures. For leaching digestion time of attack for milk, soils and sediment was 20 and 50 min for grass. Limits of detection from 0.68 to 4.4 Bq kg−1 were obtained for leaching procedures. Acceptable repeatability and between day reproducibility of the proposed method was obtained with a coefficient of variance less than 5% except for the sediment matrix.