Precise isotope analysis for sub-nanogram lead by total evaporation thermal ionization mass spectrometry (TE-TIMS) coupled with 204Pb-207Pb double spike method.
Precise isotope analysis for sub-nanogram lead by total evaporation thermal ionization mass spectrometry (TE-TIMS) coupled with 204Pb-207Pb double spike method.
复制标题
通过全蒸发热电离质谱 (TE-TIMS) 结合 204Pb-207Pb 双尖峰法对亚纳克铅进行精确同位素分析。
DOI：
10.1039/c6ja00455e
复制
发表时间：
2017
影响因子：
3.4
通讯作者：
T.
中科院分区：
文献类型：
--
作者：
Fukami;Y.;Tobita;M.;Yokoyama;T.;Moriwaki;R.;Usui;T.
我们提出了一种新的分析技术，通过总蒸发热电离质谱（TE-TIMS）与204 Pb-207 Pb双尖峰耦合，用于精确的同位素测量亚纳克的铅。由于204 Pb+在天然样品中具有最低的同位素丰度（1.4%），204 Pb+的低信号强度阻碍了具有少量（亚纳克）Pb的Pb同位素组成的精确测定。TE-TIMS的优点是测量信号强度大，测量时间短。在这项研究中，我们研究了优化的分析协议，铅同位素测量的TE-TIMS耦合与204 Pb-207 Pb双加标，包括样品加载技术，灯丝温度控制，和减少方法的同位素数据采集。Pb同位素分析的加热速率为18、90和450 mA min−1，测量时间较短，分别为60、30和20分钟。由此产生的Pb同位素比值的再现性与先前的技术相当，包括202 Pb-205 Pb双尖峰方法和204 Pb-207 Pb双尖峰方法，其使用具有最先进的1013 Ω电阻器的放大器来收集204 Pb信号。通过我们的方法测量的NIST 981的绝对Pb同位素比由于在>1250 °C的灯丝温度下发生的异常207 Pb行为以及法拉第杯的劣化而有偏差。然而，我们证实，准确的绝对铅同位素比值为未知的样品可以通过标准化的观察到的铅同位素比值的NIST 981，在同一分析期间确定，然后乘以NIST 981的参考铅同位素比值。对JB-3标准岩石样品的铅同位素比值进行了测定，结果与前人报道的结果一致。我们的结论是，我们的方法是特别适合于亚纳克的铅的同位素分析，并使用204 Pb-207 Pb双加标代替202 Pb-205 Pb双加标是有益的一些实验室由于尖峰的可用性。此外，与以前的研究相比，减少测量时间有助于测量大量样品。
We present a new analytical technique for precise isotope measurement of sub-nanograms of Pb by total evaporation thermal ionization mass spectrometry (TE-TIMS) coupled with a 204Pb–207Pb double spike. The precise determination of Pb isotopic composition with a small (sub-nanograms) quantity of Pb is hampered due to the low signal intensity of 204Pb+, which has the lowest isotope abundance in natural samples (1.4%). The advantage of TE-TIMS is that the measured signal intensities are larger and the measurement time is shorter than those by the measurement with constant filament current. In this study, we investigated optimization of the analytical protocol for Pb isotope measurement by TE-TIMS coupled with a 204Pb–207Pb double spike, including the sample loading technique, filament temperature control, and the reduction method of isotope data acquired. The Pb isotope analysis was performed with the heating rate of 18, 90, and 450 mA min−1, with a short measurement time of 60, 30, and 20 minutes. The resulting reproducibilities of Pb isotope ratios were comparable to those of previous techniques including the 202Pb–205Pb double spike method and the 204Pb–207Pb double spike method using an amplifier with a state-of-the-art 1013 Ω resistor for collecting the 204Pb signal. The absolute Pb isotope ratios for NIST 981 measured by our method were biased due to anomalous 207Pb behavior occurring at the filament temperature of >1250 °C as well as the deterioration of Faraday cups. However, we confirmed that the accurate absolute Pb isotope ratios for an unknown sample can be obtained by normalizing the observed Pb isotope ratios to those of NIST 981 that are determined in the same analytical period and then multiplying the reference Pb isotope ratios of NIST 981. We measured the Pb isotope ratios of a standard rock material JB-3, of which the results were consistent with those reported by previous studies. We conclude that our method is suitable especially for the isotope analysis of sub-nanograms of Pb, and using a 204Pb–207Pb double spike instead of a 202Pb–205Pb double spike is beneficial for a number of laboratories due to the availability of the spikes. Furthermore, reduced measurement time compared to previous studies is helpful for measuring a large quantity of samples.