Radioactive strontium-90 scattered by a nuclear power plant accident was specifically quantified by conventional inductively coupled plasma quadrupole mass-spectrometry (ICP-QMS) preceded by online chelate column separation (based on lab-on-valve) and oxygen reaction (designated the cascade step). The proposed system overcomes the isobaric interference of 90 Zr, whose soil concentration exceeds that of 90 Sr by more than six orders of magnitude. In addition, the system requires no ultimate mass spectrometry or radioactive 90 Sr standards. The radioactive 90 Sr standard was replaced with the stable isotope 88 Sr as a pseudo-standard. The modified ICP-QMS system yielded a precise, reproducible sharp 90 Sr peak in the ICP-MS profile. The elution time of 90 Sr was highly reproducible (RSD ¼ 0.5%).After implementing the cascade-step, the detection limit (DL) was 2.3 Bq L À1 (equivalent to 0.46 ppq as 90 Sr). Analysis of microwave-digested soil yielded a DL of 3.9 Bq kg À1 (equivalent to 0.77 ppq as 90 Sr).The 90 Sr from environmental contaminated soil samples collected from areas at a distance of 10 and 20 km from the Fukushima Daiichi nuclear power plant ranged from 52 Bq kg À1 to 73 Bq kg À1 , with no statistical difference between the proposed and general methods at 95% confidence level. The proposed method offers an attractive alternative use for ICP-other ionization mass spectrometry as an enrichment or purification step, thereby expanding the scope of ICP-mass-spectrometric analysis.
Intercalation of water was observed in a layered perovskite compound, NaEuTiO4, leading to its hydrated derivatives. There are some metastable intermediates in the hydrated derivatives. The hydration process includes several steps that are topotactic. The crystal structure of the hydrated derivatives was identified by Rietveld analysis for the powder X-ray diffraction pattern. It is confirmed that the water molecules are inserted into the sodium layer of NaEuTiO4.
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