Project Research Center for Fundamental Sciences, Graduate School of Science, Osaka University , 1-1 Machikaneyama, Toyonaka-shi, Osaka 560-0043, Japan.
Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo , 3-8-1 Komaba, Meguro-ku, Tokyo 153-0041, Japan.
Anal Chem. 2017 Jul 18;89(14):7535-7540. doi: 10.1021/acs.analchem.7b01299. Epub 2017 Jul 7.
Helium isotope determination may be useful in measuring volcanic activity and issuing earlier warnings of possible eruptions. A method is presented for measuring the He/He ratio in a gas sample using a multiturn time-of-flight mass spectrometer "infiTOF". In contrast to conventional waveform averaging, peaks are determined by counting ion pulses from each time-of-flight trigger. Samples were also measured by conventional magnetic-sector mass spectrometry for comparison. Magnetic sector results were used to designate a standard for infiTOF measurement and to calculate a ratio for each sample measured by infiTOF. Mass assignment error for ultrapure He standard was 4.30 × 10 Da. Mass assignment error of He and He for sample cylinders was 3.00 × 10 Da and 2.25 × 10 Da, respectively. Abundance ratios determined by infiTOF were found to be within 2% of the abundance ratios determined by magnetic-sector mass spectrometry. Mass drift was <50 × 10 Da over 10 h. Sample flow rate was not found to affect the results as long as the reference sample was analyzed under the same conditions. Results indicate that the infiTOF system may be a viable tool for measuring helium isotopes, which may eventually lead to earlier warnings of volcanic activity.
氦同位素测定可能有助于测量火山活动并更早发出可能爆发的警报。本文提出了一种使用多圈飞行时间质谱仪“infiTOF”测量气体样品中 He/He 比的方法。与传统的波形平均法不同，通过对每个飞行时间触发的离子脉冲进行计数来确定峰。还通过传统的磁扇区质谱法对样品进行了测量以进行比较。磁扇区结果用于为 infiTOF 测量指定标准，并为 infiTOF 测量的每个样品计算比值。超纯 He 标准的质量分配误差为 4.30×10 Da。样品瓶中 He 和 He 的质量分配误差分别为 3.00×10 Da 和 2.25×10 Da。通过 infiTOF 确定的丰度比与通过磁扇区质谱法确定的丰度比相差 2%以内。在 10 小时内，质量漂移小于 50×10 Da。只要参考样品在相同条件下进行分析，就不会发现样品流速会影响结果。结果表明，infiTOF 系统可能是测量氦同位素的可行工具，这最终可能导致更早地发出火山活动警报。
