Determination Of ~(90)sr In Soil Samples Using Inductively Coupled Plasma Mass Spectrometry Equipped With Dynamic Reaction Cell (icp-drc-ms)

摘要

A rapid method is reported for the determination of ~(90)Sr in contaminated soil samples in the vicinity of the Chernobyl Nuclear Power Plant by ICP-DRC-MS. Sample preparation and measurement procedures focus on overcoming the isobaric interference of ~(90)Zr, which is present in soils at concentrations higher by more than six orders of magnitude than ~(90)Sr. Zirconium was separated from strontium in two steps to reduce the interference by ~(90)Zr~+ ions by a factor of more than 10~7: (ⅰ) by ion exchange using a Sr-specific resin and (ⅱ) by reaction with oxygen as reaction gas in a dynamic reaction cell (DRC) of a quadrupole ICP-MS. The relative abundance sensitivity of the ICP-MS was studied systematically and the peak tailing originating from ~(88)Sr on mass 90 u was found to be about 3 × 10~(-9). Detection limits of 4 fg g~(-1) (0.02 Bq g~(-1)) were achieved when measuring Sr solutions containing no Zr. In digested uncontaminated soil samples after matrix separation as well as in a solution of 5 μg g~(-1) Srand 50 ng g~(-1) Zr a detection limit of 0.2 pg g~(-1) soil (1 Bq g~(-1) soil) was determined. ~(90)Sr concentrations in three soil samples collected in the vicinity of the Chernobyl Nuclear Power Plant were 4.66 ± 0.27, 13.48 ± 0.68 and 12.9 ± 1.5 pg g~(-1) corresponding to specific activities of 23.7 ± 1.3, 68.6 ±3.5 and 65.6 ± 7.8 Bq g~(-1) respectively. The ICP-DRC-MS results were compared to the activities measured earlier by radiometry. Although the ICP-DRC-MS is inferior to commonly used radiometric methods with respect to the achievable minimum detectable activity it represents a time- and cost-effective alternative technique for fast monitoring of high-level ~(90)Sr contamination in environmental or nuclear industrial samples down to activities of about 1 Bq g~(-1).