Abstract
A novel method for the determination of ultra-trace level 90Sr has been recently developed applying thermal ionization mass spectrometry (TIMS). The method includes the chemical separation of Zr (isobaric interference of 90Zr) from the samples followed by determination of 90Sr/88Sr abundance sensitivity (2.1 × 10−10). The analytical performance of this method was assessed in the IAEA-TEL 2017-3 worldwide open proficiency test. For 90Sr determination, tap water and milk powder samples were distributed amongst the participant laboratories with reference values of 11.2 ± 0.3 Bq kg−1 (2.2 ± 0.1 fg g−1) and 99.9 ± 5.0 Bq kg−1 (19.5 ± 1.0 fg g−1), respectively. The stable Sr concentrations were 39.4 ± 0.9 ng g−1 and 2.5 ± 0.1 µg g−1 while the 90Sr/88Sr isotope ratios were 6.47 ± 0.17 × 10−8 and 9.04 ± 0.45 × 10−9 in the tap water and milk powder samples, respectively. For TIMS measurement, 50 mL water and 1 g milk powder samples were taken for analysis. This TIMS method demonstrated an impressive accuracy (relative bias of 4.2% and −2.1%, respectively) and precision (relative combined uncertainty of 4.1% and 7.6%, respectively) when compared with radiometric techniques. For the first time in the history of inorganic mass-spectrometry, 90Sr analysis using a TIMS instrument is confirmed by an independent proficiency test.
Highlights
The 90Sr is an artificial isotope of strontium (Sr) whereas natural Sr comprises of four stable isotopes such as, 84Sr, 86Sr, 87Sr and 88Sr. 88Sr has the highest abundance of 82.58%
In 2017, the IAEA-TEL-2017 World-Wide Open Proficiency Test was organized by the Reference Materials Group of the IAEA Terrestrial Environment Laboratory, Seibersdorf, Austria, in order to monitor the analytical capabilities and reveal gaps in analytical methodologies of different radioanalytical laboratories[13]
Each measurement produced results with excellent accuracy and precision compared to the reference values of 11.2 ± 0.3 (2.2 ± 0.1 fg g−1) and 99.9 ± 5 Bq kg−1 (19.5 ± 1.0 fg g−1), respectively. These results demonstrated the robust analytical capacity of thermal ionisation mass spectrometry (TIMS) for 90Sr analysis
Summary
The 90Sr is an artificial isotope of strontium (Sr) whereas natural Sr comprises of four stable isotopes such as, 84Sr, 86Sr, 87Sr and 88Sr. 88Sr has the highest abundance of 82.58%. In recent years, owing to significant developments on sample introduction, detector and interference removal techniques, many successful 90Sr determinations have been reported using mass spectrometry instruments. The second critical point for the application of mass spectrometry instruments for 90Sr determination is the peak tailing on the higher mass side from 88Sr. there exists reliable ultra-high vacuum condition (
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