Study on a New Open Tubular Capillary Liquid Chromatography(OTCLC) System Based on Micro-Phase Separation of Mixed Solvents

所提出的开管毛细管液相色谱（OTCLC）系统利用了最近发现的一些有机-水混合溶剂的“微非均质性”和在这些混合溶剂中观察到的盐析相分离现象。例如，乙腈可以与水以任何比例混溶；然而，在其水混合物的分子水平上已观察到非均质性。当适当盐浓度的乙腈-水混合物被泵入这样的毛细管中时，微相分离很可能发生在毛细管壁附近，即附着在毛细管内壁的富水相中。换句话说，在毛细管内壁上动态地形成一种与流动相具有相当不同性质的液膜。当分析物的混合物被注入毛细管时，分析物的参与发生在流动相和液膜之间，提供了所提出的色谱系统的分离能力。色谱仪清楚地证明了OTCLC系统分离中性化合物和带电化合物的能力。此外，还可以分离出分子结构相似但带不同电荷的化合物。洗脱顺序可以很容易地用保留机制来解释。对硝基苯胺被有效地萃取到上层（乙腈富集）相，而2,7- nds留在下层（水富集）相，证实了所观察到的洗脱顺序。流动相中乙腈含量较高，对1-萘酚的洗脱时间略有增加，但对2,6-萘二磺酸的洗脱时间显著增加。更有趣的是，在没有NaCl的情况下，两种情况（AN/aq 9/1和AN/aq 8/2）都没有分离，这表明在毛细管中需要额外的电解质进行微相分离。

The proposed open tubular capillary liquid chromatography(OTCLC) system utilizes the recent discoveries of "microheterogeneity" in some organic-water mixed solvents and salting-out phase separation phenomena observed in these mixed solvents. For example, acetonitrile is miscible with water at any ratio ; heterogeneities, however, have been observed at a molecular level in its water mixtures. When an acetonitrile-water mixture of suitable salt concentration is pumped into such a capillary micro-phase separation is likely happening in the vicinity of the capillary wall, in a water-enriched aqueous phase attached to the capillary inner wall. In other words, a liquid membrane that has considerably different properties from the mobile phase is dynamically formed on the inner wall of the capillary.When a mixture of analytes is injected into the capillary, participation of the analytes occurs between the mobile phase and the liquid membrane, providing the separation power of the proposed chromatograpy system.Chromatographs clearly demonstrated the ability of separating neutral compounds from charged compounds by the OTCLC system. Moreover, it was also possible to separate compounds of similar molecular structure but different charges. The elution orders can readily be explained by the retention mechanism. p-Nitroaniline is effectively extracted to the upper (acetonitrile-enriched) phase while 2,7-NDS remains in the lower (water-enriched) phase, confirming the elution order observed. The high concentration of acetonitrile content in the mobile phase slightly increased the elution time of 1-naphthol but significantly increased the elution time of 2,6-naphtalene disulfonic acid. More interestingly, at the absence of NaCl, no separation in both cases (AN/aq 9/1 and AN/aq 8/2) were observed, demonstrating the necessity of additional electrolyte for the micro-phase separation in the capillary tubing.