热电离飞行时间质谱仪性能评价

本工作介绍了实验室自制的热电离飞行时间质谱仪(TI-TOF-MS)的基本结构、仪器运行参数和性能特点等。离子源产生的离子在推斥电压作用下进入聚焦透镜,然后进入垂直引入反射式的飞行时间质量分析器,最后到达检测器。信号通过数据采集卡处理后传输给计算机,采用编写的LabVIEW软件采集信号和处理数据。结果表明:仪器可测量的质量范围为m/z6~320,在m/z208位置的质量分辨率可达2 000,2h质量稳定性为7.76×10-5,测量207 Pb/206 Pb、207 Pb/206 Pb和207 Pb/206 Pb同位素比值的精密度分别为0.85%、0.27%和0.55%。该仪器在研究热电离离子源电离行为、同位素比值测定和多原子离子信号监测等方面具有广泛的应用前景。

Performance Evaluation for Thermal Ionization Time of Flight Mass Spectrometer

Thermal ionization mass spectrometry (TIMS) is one of the oldest mass spectrometric techniques, mostly applied in the precise and accurate measurement of isotopic ratios for different elements. Time of flight mass spectrometry (TOF-MS) has an unlimited mass range and an ability to rapidly obtain mass spectra relevant for the fast analysis of transient signals. By combining thermal ionization source with time-of-flight mass spectrometer, a thermal ionization time of flight mass spectrometer (TI-TOF-MS) was self-established. The performance of this instrument and the potential applications were evaluated. Samples were dropped on the metal rhenium, single or triple filament structure was used depend on the analysis element. Ions, produced by ionizing the elements loaded on the filament, pass through the ion focus lens and transport to the time-of-flight mass analyzer for detection. The analysis performance of TI-TOF-MS was comprehensively tested. The instrument has the ability to detect all the elements from m/z 6 to m/z 320, which covers all the elements can be ionized by the thermal ionization source. The resolution of instrument can reach 2 000 at m/z 208. The mass stability of instrument is test in 2 h is 7.76×10^-5 for ²⁰⁸Pb. The precision acquired for ²⁰⁴Pb/²⁰⁶Pb, ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios are 0.85%, 0.27% and 0.55%, respectively, which depend on the calculate method. During the thermal ionization process of uranium, the signal of ²³⁸U⁺、 ²³⁸U¹⁶O⁺ and ²³⁸U¹⁶O₂⁺ were measured on the spectrum. The instrument can also record the change of different kinds of ions. Compare to the commercial instrument, the home made TI-TOF-MS has a large step to grow up. But this instrument is capable for studying the thermal ionization process of different elements, monitoring the purities in the samples, and rapidly detecting the isotope ratio at a low cost. The future work should focus on the improvement of stability and the application on the TI-TOF-MS.