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

开管毛细管液相色谱(OTCLC)系统利用了最近在一些有机-水混合溶剂中发现的“微非均相”和在这些混合溶剂中观察到的盐析相分离现象。例如，乙腈与水在任何比例下都是相容的；然而，在其水混合物中，在分子水平上观察到了异质性。当适当浓度的乙腈-水混合物被泵入这种毛细管中时，很可能在毛细管壁附近的附着在毛细管内壁的富水水相中发生微相分离。换言之，在毛细管内壁上动态形成了一个与流动相性质有很大不同的液膜。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。色谱仪清楚地展示了OTCLC系统分离中性和带电化合物的能力。此外，分离分子结构相似但电荷不同的化合物也是可能的。洗脱顺序可以很容易地用保留机制解释。对硝基苯胺被有效地萃取到上相(乙腈富集相)，而2，7-NDS保留在下相(富水相)，证实了观察到的洗脱顺序。流动相中乙腈浓度较高时，1-萘酚的洗脱时间略有增加，而2，6-萘二磺酸的洗脱时间显著增加。更有趣的是，在没有氯化钠的情况下，两种情况(AN/AQ 9/1和An/AQ 8/2)都没有观察到分离，这表明在毛细管中需要额外的电解质来进行微相分离。

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.