全蒸発熱イオン質量分析法による塩素-37/塩素-35同位体比測定における塩素ブランクの評価

概要

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We report the analytical method for chlorine isotope (^<37>Cl/^<35>Cl) by total evaporation thermal ionization mass spectrometry (TE-TIMS). Replicate analyses of CsCl standard solution and seawater chloride yielded an analytical reproducibility for ^<37>Cl/^<35>Cl better than 0.2‰ for 2μgCl. Reproducibility seems to be strongly controlled by counting statistics of total amounts of Cs_2 ^<35>Cl^+(m/e=301) and Cs_2 ^<37>Cl^+(m/e=303) ion beam intensities integrated by Faraday cups. Blank loading runs using CsNO_3 without chlorine yielded chlorine blanks derived from mass interferences from filament and activator with a little higher ^<37>Cl/^<35>Cl ratio than the median of the CsCl standard isotopic ratio. The signal of chlorine blank, (less than 3×10^<-15>A), however, was too low to be detected by Faraday cups. Thus, it is unlikely that the blank signal influences the measured value of chlorine isotope ratio for the sample with more than several hundred nano-g of chlorine.
国立科学博物館の論文
2004-12-22