Yokochi Reika, Heraty Linnea J, Sturchio Neil C
Department of Earth and Environmental Sciences, University of Illinois at Chicago, 845 West Taylor Street, Chicago, MC186, SES2440, Illinois, USA.
Anal Chem. 2008 Nov 15;80(22):8688-93. doi: 10.1021/ac801804x. Epub 2008 Oct 24.
Radiokrypton isotopes ((81)Kr and (85)Kr) are ideal tracers and chronometers of various environmental processes. Atom trap trace analysis (ATTA) is capable of determining the ultralow isotopic abundances of radiokryptons (<10(-12)) provided that 50 microL of pure Kr is available. The analysis by using ATTA of (81)Kr in naturally occurring gases of interest, e.g., dissolved gases in hydrological reservoirs, requires separation of parts-per-million (ppm) level Kr from chemically airlike bulk gas. A newly developed Kr purification system is based on conventional cryogenic distillation and gas chromatography to which continuous monitoring of gas effluent composition using a quadrupole mass spectrometer brings significant advantages. Simple cryogenic distillation is controlled based on the evolution of N2/Ar ratio that is relatively constant in naturally occurring, inorganic gas. Gas chromatographic separation of parts-per-million by volume (ppmv) level Kr from up to a few liters of bulk gas can be achieved by concentrating the Kr under the chromatographic tails of major components. The system described here is capable of extracting Kr of >98% purity from 5-125 L STP (standard temperature and pressure) of bulk gas with >90% yield within several hours. This system is generally useful for separation of microliter amounts of unreactive trace volatile compounds from large-volume gas samples.
放射性氪同位素（(^{81}Kr)和(^{85}Kr)）是各种环境过程的理想示踪剂和计时工具。原子阱痕量分析（ATTA）能够测定放射性氪的超低同位素丰度（(<10^{-12})），前提是有50微升的纯氪可用。使用ATTA分析感兴趣的天然气体中的(^{81}Kr)，例如水文储层中的溶解气体，需要从化学性质类似空气的大量气体中分离出百万分之一（ppm）水平的氪。一种新开发的氪纯化系统基于传统的低温蒸馏和气相色谱法，利用四极质谱仪对气体流出物成分进行连续监测带来了显著优势。简单的低温蒸馏基于天然无机气体中相对恒定的(N_2/Ar)比值的变化进行控制。通过在主要成分的色谱尾峰下浓缩氪，可以从多达几升的大量气体中实现体积百万分之一（ppmv）水平的氪的气相色谱分离。这里描述的系统能够在几小时内从5 - 125升标准温度和压力（STP）的大量气体中提取纯度>98%的氪，产率>90%。该系统通常可用于从大量气体样品中分离微量的惰性痕量挥发性化合物。
