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.

No abstract

Online solid-phase extraction (SPE) coupled with inductively coupled plasma mass spectrometry (ICPMS) is a useful tool in automatic sequential analysis. However, it cannot simultaneously quantify the analytical targets and their recovery percentages (R%) in one-shot samples. We propose a system that simultaneously acquires both data in a single sample injection. The main flowline of the online solid-phase extraction is divided into main and split flows. The split flow line (i.e., bypass line), which circumvents the SPE column, was placed on the main flow line. Under program-controlled switching of the automatic valve, the ICPMS sequentially measures the targets in a sample before and after column preconcentration and determines the target concentrations and the R% on the SPE column. This paper describes the system development and two demonstrations to exhibit the analytical significance, i.e., the ultratrace amounts of radioactive strontium ( 90 Sr) using commercial Sr-trap resin and multielement adsorbability on the SPE column. This system is applicable to other flow analyses and detectors in online solid phase extraction.

Thermal ionization mass spectrometry (TIMS) was used to directly quantify an ultratrace of radioactive 90 Sr in microliter droplet samples. No chemical separation was required in removing isobaric interferences on M = 90 such as 90 Zr and organic molecules in the mass spectrum because the difference in evaporation and ionization (emission) temperature among organic molecules, Zr and Sr, allows us to control the emission manner and significantly suppress the isobaric interferences. Direct quantification was achieved by improving the intercalibration of Faraday cups and ion counting in an isotope dilution (ID) method. Furthermore, the use of a total evaporation method (TE) enhanced the detection efficiency by the complete collection of the 90 Sr ion beam from the samples and minimized the complexity of the fractionation effect in the isotope ratio calculation. In this study, 1 fg of 90 Sr (equal to activity of 5 millibecquerel (mBq)) in a very low-volume sample with 10 8 times greater isobaric interference from 90 Zr was successfully measured using the proposed ID-TE-TIMS method. The limit of detection was 0.029 fg (equal to 0.15 mBq) without any preconcentration. To demonstrate the wide usability of this method, low-volume samples of tears, eyelashes, saliva, environmental standards, and water samples (i.e., seawater and ground water) were analyzed within 1 h. The relationship of the measured values between this ID-TE-TIMS method and a radiometric analysis was shown to have good linearity.