West C, Lesellier E
LETIAM, Groupe de Chimie Analytique de Paris Sud (EA 3343), IUT d'Orsay, Plateau du Moulon, 91400 Orsay, France.
J Chromatogr A. 2006 Mar 31;1110(1-2):181-90. doi: 10.1016/j.chroma.2006.01.125. Epub 2006 Feb 17.
Varied types of alkylsiloxane-bonded and fluoroalkylsiloxane-bonded stationary phases, all commercially available, were investigated with subcritical fluid mobile phase. The effect of the alkyl chain length (from C4 to C18) and of the nature of the bonding (fluorodecylsiloxane, phenyl-C18 and polar-embedded-C18) on the chromatographic behaviour was investigated by the use of a linear solvation energy relationship (LSER), the solvation parameter model. A large set of test compounds provides precise and reliable information on the intermolecular interactions responsible for retention on these stationary phases used with a subcritical mobile phase. First of all, the results underline the close properties between subcritical fluid and organic liquid. The use of non aqueous mobile phases reduces the cavity energy and the mobile phase acidity generally encountered with aqueous liquid phases, allowing other interactions to take a part in retention. As expected, an increase in the alkyl chain length favours the dispersive interactions between the solutes and the stationary phases. Changes in basicity and acidity of the stationary phases are also related to the chain length, but, in this case, mobile phase adsorption onto the stationary phase is supposed to explain these behaviours. The addition of a phenyl group at the bottom of the C18 chain, near the silica, does not induce great modifications in the retentive properties. The fluorodecylsiloxane and the polar-embedded alkylsiloxane phases display very different properties, and can be complementary to the classical alkylsiloxane-bonded phases. In particular, the fluorinated phase does not favour the dispersive interactions, in comparison to hydrogenated stationary phases, when the basicity of the polar-embedded phase is obviously greater than the one of classical alkylsiloxane-bonded phases, due to the amide function. Finally, logk-logk curves plotted between the different phases illustrate the effect of the interaction properties on the retention of different classes of compounds.
研究了各种类型的烷基硅氧烷键合和氟代烷基硅氧烷键合固定相（均为市售产品）在亚临界流体流动相条件下的情况。通过使用线性溶剂化能关系（LSER）即溶剂化参数模型，研究了烷基链长度（从C4到C18）以及键合性质（氟代癸基硅氧烷、苯基-C18和极性嵌入-C18）对色谱行为的影响。大量的测试化合物提供了有关在亚临界流动相条件下这些固定相上保留作用所涉及的分子间相互作用的精确且可靠的信息。首先，结果强调了亚临界流体与有机液体之间的相似性质。使用非水流动相降低了通常在水相流动相中遇到的空穴能和流动相酸度，使得其他相互作用能够参与保留过程。正如预期的那样，烷基链长度的增加有利于溶质与固定相之间的色散相互作用。固定相碱度和酸度的变化也与链长度有关，但在这种情况下，流动相在固定相上的吸附被认为可以解释这些行为。在靠近硅胶的C18链底部添加苯基不会引起保留性质的重大改变。氟代癸基硅氧烷相和极性嵌入烷基硅氧烷相表现出非常不同的性质，并且可以与经典的烷基硅氧烷键合相互补。特别是，与氢化固定相相比，氟化相不利于色散相互作用，而极性嵌入相的碱度明显大于经典烷基硅氧烷键合相，这是由于酰胺官能团的缘故。最后，不同相之间绘制的logk-logk曲线说明了相互作用性质对不同类别化合物保留的影响。
