In situ isotopic analysis of uranium using a new data acquisition protocol for 10^13 ohm Faraday amplifiers
In situ isotopic analysis of uranium using a new data acquisition protocol for 10^13 ohm Faraday amplifiers
复制标题
使用 10^13 欧姆法拉第放大器的新数据采集协议对铀进行原位同位素分析
DOI：
10.1039/d0ja00498g
复制
发表时间：
2021
影响因子：
3.4
通讯作者：
Hirata Takafumi
中科院分区：
文献类型：
--
作者：
Yamamoto Kota;Asanuma Hisashi;Takahashi Hiroaki;Hirata Takafumi
用激光烧蚀多接收电感耦合等离子体质谱法（LA-MC-ICP-MS）对一系列固体材料进行了235 U/238 U和234 U/238 U同位素比值的测量。为了扩展同位素比测量的动态范围，采用具有不同放大增益的三个法拉第检测器（具有1011和1013欧姆电阻的放大器）。为了减少采样体积，对通过短时间LA持续时间（<3 s）获得的瞬态信号进行同位素比测量。从使用LA技术获得的瞬态信号中，测量的235 U/238 U比率比采用常规tau校正技术时文献中记录的值高约3%。这主要是由于对法拉第放大器的慢响应的不完全校正。为了克服这一点，连续离子监测，而不是tau校正，应用于从瞬态信号的同位素比测量。235 U/238 U和234 U/238 U比值测量的典型精度分别为1‰和7%（2SD），锆石和玻璃材料的235 U/238 U比值与文献中观察到的值吻合良好。同位素比值测量结果表明，235 U/238 U比值的不均匀性之间的钛铁矿颗粒。测量的234 U/238 U比值与238 U系列中的长期平衡值一致，除了FCT钛铁矿。本文还讨论了长期平衡中~（234）U/~（238）U比值与实测值不一致的可能原因。在这项研究中获得的数据表明，目前的数据采集协议可以作为一个基准技术同位素比测量来自瞬态信号使用法拉第检测器，特别是当使用高增益（如1013欧姆电阻）放大器。
Isotopic ratio measurements for 235U/238U and 234U/238U ratios were made for a series of solid materials using laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). To extend the dynamic range of the isotopic ratio measurements, three Faraday detectors with different amplification gains (amplifiers with 1011 and 1013 ohm resistors) were employed. To reduce the sampling volume, isotopic ratio measurements were made on transient signals obtained by short-time LA duration (<3 s). From the transient signals obtained using the LA technique, measured 235U/238U ratios were approximately 3% higher than values noted in the literature when a conventional tau correction technique was employed. This was mainly due to incomplete correction of the slow response of the Faraday amplifiers. To overcome this, continuous ion-monitoring, rather than tau correction, was applied to the isotopic ratio measurements from the transient signals. Typical precision for the 235U/238U and 234U/238U ratio measurements were 1‰ and 7% (2SD), respectively, and the resulting 235U/238U ratios for zircons and glass materials showed good agreement with values observed in the literature. The isotopic ratio measurements revealed heterogeneity of 235U/238U ratios among titanite grains. The measured 234U/238U ratios were consistent with the value of the secular equilibrium in the 238U series, except for FCT titanite. Herein, a possible cause for the discrepancy in the measured 234U/238U ratio in the secular equilibrium is discussed. The data obtained in this study demonstrate that the present data acquisition protocol can serve as a benchmark technique for isotopic ratio measurements derived from transient signals using Faraday detectors, particularly when using high-gain (e.g. 1013 ohm resistors) amplifiers.