A new method for calibrating the current gain of 10(13) Omega amplifiers in thermal ionization mass spectrometry
A new method for calibrating the current gain of 10(13) Omega amplifiers in thermal ionization mass spectrometry
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热电离质谱中10(13) Omega放大器电流增益校准的新方法
DOI：
10.1002/jms.4079
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发表时间：
2018
影响因子：
2.3
通讯作者：
Liu Wengui
中科院分区：
文献类型：
--
作者：
Wang Guiqin;Zeng Yuling;Xu Jifeng;Liu Wengui
我们报告了一种在热电离质谱 (TIMS) 中使用的正负模式下校准 1013Ω 放大器电流增益的新方法。该方法使用任何同位素标准品或样品来校准增益因子，只要它能产生稳定的电流信号即可。它比 Thermo-Fisher（TIMS 制造商）推荐的更简单、更灵活。在这些分析中，评估了五个 1013Ω 放大器的增益。一天内增益因子的精度优于 100 ppm (2 RSD)，2 至 8 个月内的长期重现性优于 300 ppm (2 RSD)。校准增益后，在 88Sr 强度下，NIST 987 Sr 的 87Sr/88Sr 和 La Jolla Nd 的 143Nd/144Nd 的比率准确度和精密度分别为 0.710242 ± 60 (2 SD,n= 14) 和 0.511842 ± 10 (2 SD,n= 22)。 0.3 V 和 142 Nd 0.4 V，而在负模式下，Merck Os 的 187Os/188Os 为 0.120229 ± 34 (2 SD,n=23)，强度为 187OsO30.01 mV。此外，还认识到负模式 TIMS (NTIMS) 和正模式 TIMS (PTIMS) 之间增益因子的差异。本研究中，NTIMS 和 PTIMS 的增益因子值在 Triton 上的偏差为 0.54%，在 Triton Plus TIMS 上的偏差为 0.31%；因此，NTIMS和PTIMS均应进行增益校准。此外，对于同一 1013Ω 放大器，检测到 H 和 L 法拉第杯之间存在 ~ 1.5 × 10−5 的偏差，这表明不同法拉第杯的效率可能会影响增益系数，而这种偏差可以通过本研究中描述的“交叉校准”新方法来消除。
We report a new method for calibrating the current gain of 1013Ω amplifiers in both positive and negative mode used in thermal ionisation mass spectrometry (TIMS). This method uses any isotopic standard or sample to calibrate the gain factor as long as it can produce a stable current signal. It is simpler and more flexible than that recommended by Thermo‐Fisher (the manufacture of the TIMS). In these analyses, the gains of five 1013Ω amplifiers were assessed. The precision of gain factors was better than 100 ppm (2 RSD) in a day, and the long‐term reproducibility was better than 300 ppm (2 RSD) within 2 to 8 months. After a gain was calibrated, the ratio accuracy and precision in the positive mode for87Sr/88Sr of NIST 987 Sr and143Nd/144Nd of La Jolla Nd were 0.710242 ± 60 (2 SD,n= 14) and 0.511842 ± 10 (2 SD,n= 22), respectively, at intensities of88Sr 0.3 V and142Nd 0.4 V, while in the negative mode for187Os/188Os of Merck Os was 0.120229 ± 34 (2 SD,n= 23) at an intensity of187OsO30.01 mV. In addition, a difference in the gain factors between the negative mode TIMS (NTIMS) and positive mode TIMS (PTIMS) has been recognized. The values of the gain factor for NTIMS and PTIMS show a deviation of 0.54% on the Triton and 0.31% on the Triton Plus TIMS in this study; therefore, gain calibration should be carried out on both NTIMS and PTIMS. Moreover, a bias of ~ 1.5 × 10−5between H and L Faraday cups for the same 1013Ω amplifier has been detected, hinting that the efficiency of different Faraday cups may affect the gain factors, which can be eliminated through the new method of “cross‐calibration” discribed in this study.