Estimation of surface desorption times in hydrophobically coated nanochannels and their effect on shear-driven and pressure-driven chromatography

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• 作者：Frederik Detobel ; Veronika Fekete ; Wim De Malsche ; Selm De Bruyne ; Han Gardeniers and Gert Desmet
• 关键词：Shear ; driven chromatography ; Analyte ; wall collisions ; Band broadening ; Random walk simulations
• 刊名：Analytical and Bioanalytical Chemistry
• 出版年：2009
• 出版时间：May, 2009
• 年：2009
• 卷：394
• 期：2
• 页码：399-411
• 全文大小：381.7 KB

文摘

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 μs, while they were found to be on the order of 100 to 500 μs 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.