Unexpected retention behavior of supercritical fluid chromatography at the low density near critical region of carbon dioxide

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• 作者：Abhijit Tarafder ; Georges Guiochon ; ^{guiochon@ion.chem.utk.edu}
• 关键词：Isopycnic ; SFC ; Supercritical fluid chromatography ; Operating conditions ; Retention mechanism ; Near critical
• 刊名：Journal of Chromatography A
• 出版年：2012
• 出版时间：16 March, 2012
• 年：2012
• 卷：1229
• 期：Complete
• 页码：249-259
• 全文大小：1099 K

文摘

The retention factors of octylbenzene, octadecene, anthracene, and pyrene eluted from columns packed with neat silica and C₁₈-bonded silica by pure carbon dioxide near its critical region increase with increasing temperature along low-density isopycnic lines. This behavior is markedly different from the one observed in nearby regions of the pressure-temperature diagram of CO₂, where the retention factors of these compounds decrease with increasing temperature along high-density isopycnic lines. Several possible reasons that could explain this reversal in the behavior of the retention factors are discussed. The most plausible is related to the formation of multilayer adsorption of CO₂ on the stationary phases in a density range slightly lower than the critical density.