Osmium isotope ratio measurements by negative thermal ionization mass spectrometry (NTI-MS)
Osmium isotope ratio measurements by negative thermal ionization mass spectrometry (NTI-MS)
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DOI：
10.1007/bf00328491
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发表时间：
1991-09
期刊：
影响因子：
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通讯作者：
T. Walczyk;E. Hebeda;K. Heumann
中科院分区：
文献类型：
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作者：
T. Walczyk;E. Hebeda;K. Heumann
提出了一种利用法拉第杯作为探测器的负热电离技术，可以精确测量锇的同位素比值。主要同位素的相对标准偏差在0.004% ~ 0.07%之间。低至1ng的样品以六氯酸装载。从结果中可以得出结论，在pg范围内的样品量也会产生足够的OsO3−离子流，从而避免了电子倍增器作为检测器。之所以选择h2oscl6，是因为这种化合物是地质样品中锇分离后最合适的化学形式。在离子源中引入氧或氟利昂可使OsO3−离子的排放增加10倍以上。利用氧可获得30%以上的电离效率。在氧的情况下，离子电流的稳定性比在氟利昂的情况下好。然而，这两种化合物都稳定了离子源中光学离子透镜的高压电位，这是NTI-MS中一个永久的问题。所描述的同位素比值测量是陆地和地外样品Re/Os定年的重要改进。
A negative thermal ionization technique using a Faraday cup as detector is presented, which allows precise isotope ratio measurements of osmium. For the major isotopes the relative standard deviation is in the range of 0.004% to 0.07%. Sample amounts down to 1 ng were loaded as hexachloroosmic acid. From the results it is concluded that also sample amounts in the pg range will result in sufficient ion currents of OsO3−, avoiding an electron multiplier as detector. H2OsCl6was chosen because this compound is the most suitable chemical form after separation of osmium from geological samples. The introduction of oxygen or freons into the ion source enhances the emission of OsO3−ions by a factor of up to more than ten. Ionization efficiencies of more than 30% are obtained by using oxygen. The stability of the ion current is better in the case of oxygen than in the case of freons. However, both compounds are stabilizing the high voltage potentials of the optical ion lenses in the ion source, a permanent problem in NTI-MS. The described isotope ratio measurement is an important improvement for Re/Os dating of terrestrial and extraterrestrial samples.