| Budget Amount *help |
¥3,800,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥300,000)
Fiscal Year 2007: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2006: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
We tried to develop a method for determining boron isotopic composition of solution sample using secondary ion mass spectrometer (SIMS) and applied it to a standard sample, i. e., NIST 951 and such natural samples as seawater, hot spring waters and condensation of atmospheric sample.
The solution samples were dried on silicon wafer by an infrared lamp for SIMS (NanoSIMS) analysis. During drying of the samples, previous studies have recommended an addition of boron-free seawater for suppressing loss of boron in the samples. However, our study indicates that the addition of boron-free seawater to NIST 951 standard and hot spring samples apparently decreases the beam intensity of boron isotopes compared with those without the addition of boron-free seawater. We think that the boron-free seawater addition method is not effective for NanoSIMS analysis.
As for seawater samples, we tried with/without Au (gold) coating sample preparations. The samples without Au coating showed δ^<11> B values ranging +32〜+73, which were quite different form the reported value for seawater (+39.5). On the other hand, δ^<11> B values of sample with Au coating calculated from data of NIST 951 treated by same manner showed +44〜+46, which were nearly identical with the reported value of seawater. Although further studies are required, the Au coating method may be effective for accurate boron isotopic composition analysis using NanoSIMS.
δ^<11> B values of the hot spring sample were +2.6 and +5.6, which were within the range of those of volcanic gases of Japan. The condensation of atmospheric sample collected at Ocean Research Institute, University of Tokyo showed δ^<11> B values of -5.1, -1.8 and +5.0, which is almost same as δ^<11> B value (+1.7) of sample collected at the same location.
These facts suggest that NanoSIMS could be used for accurate boron isotopic determination of natural solution samples.
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