Detobel Frederik, Fekete Veronika, De Malsche Wim, De Bruyne Selm, Gardeniers Han, Desmet Gert
Department of Chemical Engineering, Vrije Universiteit Brussel, 1050, Brussels, Belgium.
Anal Bioanal Chem. 2009 May;394(2):399-411. doi: 10.1007/s00216-009-2614-2. Epub 2009 Feb 13.
The present paper provides a detailed analysis of the analyte-wall adsorption effects in nanochannels, including a random walk study of the analyte-wall collision frequency, and uses these insights to estimate wall desorption times from chromatographic experiments in nanochannels. Using coumarin dye analytes and using a methanol/water mixture buffered at pH 3 in 120-nm deep channels, the surface desorption times on naked fused-silica glass were found to be maximally of the order of 60 to 150 mus, while they were found to be on the order of 100 to 500 mus on a hydrophobically coated wall. These nonzero adsorption and desorption times lead to an additional band broadening when conducting chromatographic separations. Shear-driven flows, requiring a noncoated moving wall and a stationary coated wall, intrinsically turn out to be more prone to this effect than pressure-driven or electro-driven flows for example. The present study also shows that, interestingly, the number of analyte-wall collisions increases with the inverse of the channel depth and not with its second power, as would be expected from the Einstein-Smoluchowski relationship for molecular diffusion.
本文详细分析了纳米通道中分析物与壁面的吸附效应，包括对分析物与壁面碰撞频率的随机游走研究，并利用这些见解从纳米通道色谱实验中估算壁面解吸时间。使用香豆素染料分析物，并在120纳米深的通道中使用pH值为3的甲醇/水混合物缓冲液，发现在裸露的熔融石英玻璃上表面解吸时间最大约为60至150微秒，而在疏水涂层壁面上则约为100至500微秒。这些非零的吸附和解吸时间在进行色谱分离时会导致额外的谱带展宽。例如，剪切驱动流需要一个未涂层的移动壁面和一个固定的涂层壁面，与压力驱动流或电驱动流相比，本质上更容易受到这种效应的影响。本研究还表明，有趣的是，分析物与壁面的碰撞次数随通道深度的倒数增加，而不是像分子扩散的爱因斯坦 - 斯莫卢霍夫斯基关系所预期的那样随通道深度的平方增加。
