Influence of particle properties on the wall region in packed capillaries.
Influence of particle properties on the wall region in packed capillaries.
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颗粒特性对填充毛细管壁区域的影响
DOI：
10.1016/j.chroma.2012.10.027
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
U. Tallarek
中科院分区：
文献类型：
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作者：
S. Bruns;D. Stoeckel;B. M. Smarsly;U. Tallarek
分析柱（4.6 mm i.d.）与常规的完全多孔颗粒相比，填充有核-壳颗粒的颗粒显示出显著降低的涡流分散对谱带加宽的贡献。据推测，这是否是由于核-壳颗粒的窄粒度分布（PSD）（作为固有优势）或由于改进的填充结构（其特别地降低了由壁效应引起的跨柱速度偏差）引起的。最近的一项模拟研究反对前一个命题[A. Daneyko等人，Anal. 83（2011）3903]。更可能的是，与具有宽PSD的完全多孔颗粒相比，用于核-壳颗粒的浆料填充过程导致具有降低的壁效应的床形态。为了获得后一个命题实验，我们浆填充毛细管柱（100μm i.d.）用不同的全多孔（宽PSD）和核-壳（窄PSD）颗粒，并使用共聚焦激光扫描显微镜对它们的床结构进行三维成像。这使我们能够解决和分析在这些列本地所有长度尺度上的床形态，有助于涡流分散。在跨柱尺度上，我们观察到核-壳和完全多孔颗粒之间的系统差异：在柱壁附近，核-壳颗粒比完全多孔颗粒堆积得更密（更接近堆积密度）并且具有更高的规则性。所有填料的散装区域实际上是不可区分的。这提供了实验证据，即核-壳填料的涡流分散贡献减少应归因于更高的跨柱均匀性，而不是在较小长度尺度上改善的床形态，例如，减少了短程紊乱
Analytical columns (4.6mm i.d.) packed with core–shell particles have shown a significantly reduced eddy dispersion contribution to band broadening compared to conventional fully porous particles. It has been speculated if this is caused by the narrow particle size distribution (PSD) of the core–shell particles, as an intrinsic advantage, or by an improved packing structure that specifically reduces the transcolumn velocity biases caused by wall effects. A recent simulation study has pointed against the former proposition [A. Daneyko et al., Anal. Chem. 83 (2011) 3903]. It is more likely that the slurry packing process for core–shell particles results in bed morphologies with reduced wall effects compared to the fully porous particles with a wide PSD. To access the latter proposition experimentally we slurry packed capillary columns (100μm i.d.) with different fully porous (wide PSDs) and core–shell (narrow PSDs) particles and imaged their bed structures three-dimensionally using confocal laser scanning microscopy. This allowed us to resolve and analyze the bed morphology in these columns locally on all length scales contributing to eddy dispersion. On the transcolumn scale we observed a systematic difference between core–shell and fully porous particles: In the vicinity of the column wall the core–shell particles packed denser (closer to the bulk packing densities) and with a higher regularity than the fully porous particles. The bulk regions of all packings were effectively indistinguishable. This provides experimental evidence that the reduced eddy dispersion contribution with core–shell packings should be attributed to a higher transcolumn homogeneity rather than to an improved bed morphology on smaller length scales, e.g., to a reduced short-range disorder.