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首页> 外文期刊>Journal of chromatography, A: Including electrophoresis and other separation methods >Unravelling the effects of mobile phase additives in supercritical fluid chromatography-Part II: Adsorption on the stationary phase
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Unravelling the effects of mobile phase additives in supercritical fluid chromatography-Part II: Adsorption on the stationary phase

机译：在超临界流体色谱 - 第二部分中解吸流动相添加剂的影响 - 第二部分：固定阶段的吸附

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摘要

The mobile phases employed in current practice of supercritical fluid chromatography (SFC) are usually composed of a mixture of pressurized carbon dioxide and a co-solvent. The co-solvent is most often an alcohol and may contain a third component in small proportions, called an additive (acid, base or salt). In the first part of this series, the effects of mobile phase additives on the polarity and apparent pH of the mobile phase were explored. In the present paper, we examine the effects pertaining to adsorption of additives on the stationary phase. Ammonium acetate was selected as a representative case, because it is often employed in current practice. To favour its solubility and further improve chromatographic quality, a small portion of water is also advocated. First, the equilibration time is observed to be largely increased in the presence of an additive, especially when mobile phase compositions containing only low proportions of methanol co-solvent are employed. Secondly, the effects of ammonium acetate are more thoroughly assessed with a modified version of the solvation parameter model (five Abraham descriptors and two descriptors to take account of positive and negative charges on ionizable species). On a hybrid silica stationary phase (ACQUITY UPC2 BEH), the effects of increasing concentration of ammonium acetate (0-25 mM in the methanol co-solvent) are investigated. The retention of acidic species is the most strongly affected, with a continuous retention increase when additive concentration increases. The retention of basic and neutral species is also moderately affected. Then thirty-two stationary phases based on sub-2 mu m totally porous particles or sub-3 mu m superficially porous particles are characterized with and without 20 mM ammonium acetate and 2% water in the methanol co-solvent. The effects of adsorbed additive on the interaction capabilities are discussed. Finally, the interest of introducing the additive in the dilution solvent, a method
机译：用于超临界流体色谱（SFC）的当前实践中使用的移动相通常由加压二氧化碳和共溶剂的混合物组成。共溶剂通常是醇，并且可以含有小比例的第三组分，称为添加剂（酸，碱或盐）。在本系列的第一部分，探讨了流动相添加剂对流动阶段极性和表观pH的影响。在本文中，我们研究了与静止相对添加剂的吸附有关的效果。选择乙酸铵作为代表性案例，因为它通常用于当前的实践中。为了有利于其溶解性并进一步提高色谱品质，还提倡一小部分水。首先，观察到在添加剂存在下，观察到平衡时间在很大程度上增加，特别是当使用仅含有低比例的甲醇共溶剂的流动相组合物时。其次，用溶剂化参数模型的改性版本（五个亚伯拉姆描述符和两个描述符，以考虑可电离物种的正面和负电荷）更彻底地评估乙酸铵的影响。在杂交二氧化硅固定相（Acquity UPC2 BEN）上，研究了乙酸铵浓度浓度（甲醇共溶剂中0-25mm）的影响。酸性物质的保留是最强烈的影响，当添加剂浓度增加时，连续保留增加。碱性和中性物种的保留也适度影响。然后基于亚2μm的三十次固定相，基于甲醇共溶剂中的2％乙酸铵和2％水，其特征在于，在甲醇共溶剂中表征，在没有20mM乙酸铵和2％水中的表征。讨论了吸附添加剂对相互作用能力的影响。最后，在稀释溶剂中引入添加剂的兴趣，一种方法

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