Clarke W B, Koekebakker M, Barr R D, Downing R G, Fleming R F
Department of Physics, McMaster University, Hamilton, Ontario, Canada.
Int J Rad Appl Instrum A. 1987;38(9):735-43. doi: 10.1016/0883-2889(87)90255-3.
A new technique for analysis of lithium and boron at ultratrace concentrations (less than 10(-8)g g-1) is described. The method consists of mass-spectrometric assay of 3He from decay of tritium produced by thermal-neutron reaction on 6Li, and 4He produced by thermal-neutron reaction on 10B. Two neutron-irradiation facilities were used: the McMaster reactor, which is 235U-enriched and light-water moderated; and a graphite-moderated thermal column attached to the 235U-enriched, heavy-water-moderated core at the National Bureau of Standards (NBS) reactor. In the McMaster irradiations, fast neutrons (greater than 0.2 MeV) induce the reactions 14N(n, 3H)12C, 12C(n, alpha)9Be, 16O(n, alpha)13C, and 14N(n, alpha)11B. These reactions become serious sources of error in samples such as human blood which have very low concentrations of lithium and boron, and high concentrations of nitrogen, carbon and oxygen. In the NBS thermal column, fast-neutron reactions are virtually absent, and only corrections for thermal-neutron capture by deuterium, and thermal-neutron (n, alpha) reactions on oxygen, sulfur, chlorine, potassium, and calcium need to be taken into account. Results are presented for various actual samples including human blood and its components, and some standard biological reference materials, to provide a realistic base for other workers to judge the reliability of the method.
本文描述了一种分析超痕量浓度（小于10⁻⁸ gg⁻¹）锂和硼的新技术。该方法包括对⁶Li上热中子反应产生的氚衰变产生的³He以及¹⁰B上热中子反应产生的⁴He进行质谱分析。使用了两个中子辐照设施：麦克马斯特反应堆，它是富集²³⁵U且轻水慢化的；以及国家标准局（NBS）反应堆中与富集²³⁵U、重水慢化堆芯相连的石墨慢化热柱。在麦克马斯特的辐照中，快中子（大于0.2 MeV）会引发¹⁴N(n, ³H)¹²C、¹²C(n, α)⁹Be、¹⁶O(n, α)¹³C和¹⁴N(n, α)¹¹B反应。在锂和硼浓度极低且氮、碳和氧浓度高的样品（如人血）中，这些反应会成为严重的误差来源。在NBS热柱中，几乎不存在快中子反应，只需要考虑氘对热中子的俘获以及氧、硫、氯、钾和钙上的热中子(n, α)反应的校正。给出了包括人血及其成分以及一些标准生物参考物质在内的各种实际样品的结果，为其他研究人员判断该方法的可靠性提供了现实依据。
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