National Institute of Standards and Technology, Chemical and Biochemical Reference Data Division, Gaithersburg, MD 20899-8320, USA.
J Chromatogr A. 2011 Nov 18;1218(46):8432-42. doi: 10.1016/j.chroma.2011.09.035. Epub 2011 Sep 19.
A reversed-flow gas-chromatography (RF-GC) apparatus for the measurement of binary diffusion coefficients is described and utilized to measure the binary diffusion coefficients for several systems at temperatures from (300 to 723)K. Hydrocarbons are detected using flame ionization detection, and inert species can be detected by thermal conductivity. The present apparatus has been utilized to measure diffusion coefficients at substantially higher temperatures than previous RF-GC work. Characterization of the new apparatus was accomplished by comparing measured binary diffusion coefficients of dilute argon in helium to established reference values. Further diffusion coefficient measurements for dilute helium in argon and dilute nitrogen in helium (using thermal conductivity detection) and dilute methane in helium (using flame ionization detection) were performed and found to be in excellent agreement with literature values. The measurement of these well-established diffusion coefficients has shown that specific experimental conditions are required for accurate diffusion measurements using this technique, particularly at higher temperatures. Numerical simulations of the diffusion experiments are presented to demonstrate that artifacts of the analysis procedure must be specifically identified to ensure accuracy, particularly at higher temperatures.
一种用于测量二元扩散系数的逆流气相色谱 (RF-GC) 仪器被描述并用于在从 (300 到 723)K 的温度下测量多个系统的二元扩散系数。烃类使用火焰离子化检测进行检测，而惰性物质可以通过热导检测进行检测。本仪器已用于测量比以前的 RF-GC 工作温度更高的扩散系数。通过将测量的稀氩在氦中的二元扩散系数与已建立的参考值进行比较，对新仪器进行了表征。进一步对稀氦在氩中的扩散系数和稀氮在氦中的扩散系数（使用热导检测）以及稀甲烷在氦中的扩散系数（使用火焰离子化检测）进行了测量，发现与文献值非常吻合。这些经过充分验证的扩散系数的测量表明，使用该技术进行准确的扩散测量需要特定的实验条件，特别是在较高温度下。还呈现了扩散实验的数值模拟，以证明在较高温度下，必须特别识别分析过程中的伪影以确保准确性。
