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Diffusion and Dispersion in Tubes in Supercritical Fluid Chromatography Using Sub-2 µm Packings
Chromatographia ( IF 1.2 ) Pub Date : 2021-01-02 , DOI: 10.1007/s10337-020-03996-8
Terry A. Berger

Detailed plots of diffusion coefficients, D m , versus % methanol in CO 2 and pressure, P, are presented. Using sub-2 µm particle columns with small ID connector tubing make for large pressure drops, ∆ P , across both the system and the column. This creates low average D m , and large gradients in D m , slowing the chromatography. The ∆ P with 75 µm ID tubing varies non-linearly with flow creating U shaped plots of reduced plate height versus flow rate. Plumbing does but should never change h versus F plots. Using larger ID tubes to estimate the extra-column variance $$\sigma_{e - c}^{2}$$ σ e - c 2 of smaller tubes, by keeping the aspect ratio ( L / r ) constant, assumes the same constant D m in both tubes, which is not true in SFC. Contrary to prediction, calculated tube plate count, N, indicates connector tubing is more dispersive in SFC compared to high performance liquid chromatography (HPLC). Current supercritical fluid chromatographs (SFC) have up to 20 × higher variance than appropriate for use with 2.1 and 3 mm columns ≤ 100 mm long, packed with sub-2 µm particles. Lower volume UV detector flow cells are needed for use with sub-2 µm particles. The modular nature of instruments makes it difficult to further minimize tube lengths while retaining column temperature control. Very small ID tubes, like 75 µm should probably be avoided. It remains difficult to characterize and minimize $$\sigma_{e - c}^{2}$$ σ e - c 2 .

中文翻译:

使用亚 2 µm 填料的超临界流体色谱中管中的扩散和分散

提供了扩散系数 D m 与 CO 2 中的甲醇百分比和压力 P 的详细图。使用带有小内径连接管的亚 2 µm 颗粒色谱柱会导致整个系统和色谱柱的压降 ∆ P 较大。这会产生较低的平均 D m 和较大的 D m 梯度,从而减慢色谱速度。内径为 75 µm 的管子的 ∆ P 随流量呈非线性变化,从而形成降低板高度与流速的 U 形图。管道确实但不应该改变 h 与 F 图。使用较大的 ID 管来估计较小管的柱外方差 $$\sigma_{e - c}^{2}$$ σ e - c 2,通过保持纵横比 ( L / r ) 恒定,假设相同两个管中的常数 D m,这在 SFC 中不正确。与预测相反,计算的管板数,N,表示与高效液相色谱 (HPLC) 相比,连接管在 SFC 中的分散性更强。当前的超临界流体色谱仪 (SFC) 的方差比适用于 2.1 和 3 毫米长 ≤ 100 毫米、填充亚 2 微米颗粒的色谱柱高 20 倍。与亚 2 µm 颗粒一起使用需要较小体积的 UV 检测器流通池。仪器的模块化特性使得在保持色谱柱温度控制的同时进一步缩短管长度变得困难。应该避免使用非常小的 ID 管,例如 75 µm。仍然难以表征和最小化 $$\sigma_{e - c}^{2}$$ σ e - c 2 。填充亚 2 µm 颗粒。与亚 2 µm 颗粒一起使用需要较小体积的 UV 检测器流通池。仪器的模块化特性使得在保持色谱柱温度控制的同时进一步缩短管长度变得困难。应该避免使用非常小的 ID 管,例如 75 µm。仍然难以表征和最小化 $$\sigma_{e - c}^{2}$$ σ e - c 2 。填充亚 2 µm 颗粒。与亚 2 µm 颗粒一起使用需要较小体积的 UV 检测器流通池。仪器的模块化特性使得在保持色谱柱温度控制的同时进一步缩短管长度变得困难。应该避免使用非常小的 ID 管,例如 75 µm。仍然难以表征和最小化 $$\sigma_{e - c}^{2}$$ σ e - c 2 。
更新日期:2021-01-02
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