旋轉螺管組式逆向流層析使用超臨界二氧化碳為動相之研究

Abstract

逆向流層析（Countercurrent Chromatography, CCC）自從70年代由Dr. Y. Ito 等人開發了實用的儀器以來，一直到最近商業化的設備，皆使用 了傳統的有機 / 水溶液系統來操作，由於一般樣品在液體中擴散較慢， 直接造成分離所需時間較長，而同時分離的效率也較差。本實驗改以超臨 界二氧化碳，以及水 / 甲醇為溶劑系統來操作，藉由其相對傳統溶液較 高的擴散係數，來達成改善傳統液相CCC的目的。為了將二氧化碳保持在 超臨界態下，設備必須有所改進來因應高壓系統，以往的逆向流的儀器， 多半不需要高壓，因此本實驗首先在液滴式逆相流層析中以PEKK管柱做系 統的改良測試後，從主體上參考 Ito 氏所發明旋轉螺管組式的儀器，而 後因應高壓的需求在幫浦、管柱材質及閥門組合上做了必要的修正。另外 ，系統內的液相成分，對UV檢測器亦造成相當的訊號干擾，而為此也設計 自製了一組相分離裝置（Phase separator），來除去系統中非勻相水滴 對光源折射等的干擾。本研究除了測試為因應高壓所進行的設備改進外， 同時也進行了在此一高壓系統中，以及超臨界態 / 液態的溶劑系統下， 影響相滯留比（Phase Retention Ratio）一些因子的探討，由於在分離 的過程中，相滯留比的多寡決定了層析中的樣品容量以及解析度等重要因 子，藉由這些研究可以了解逆向流的機構，乃至於找出實驗的最適化條件 。 Due to the efforts of Y. Ito et. al., practical instruments of counter-current chromatography (CCC) have been developed since 1970's that eventually resulted in commercialized equipment. However, the solvent systems that developed in the past 25 years basically remain the same, i.e., liquid/liquid for the mobile and stationary phases. Because of the relatively slow diffusion rate of sample molecules in liquid, it takes relatively long time to accomplish separation runs and accordingly end up with mediocre efficiency. In this study, supecritical fluid carbon dioxide/liquid solvent system was employed. Due to the relatively high diffusivity in supercritical fluid, the separation effciency is expected to improve substantially. To keep carbon dioxide under supercritical condition, the traditional CCC equipment required modifications, including solvent feeding and sample injection systems, tubings, and valves. In addition, the aqueous droplets carried out by carbon dioxide intermittently made considerable noise in the UV-Vis detector. Correspondingly, a simple phase separator was introduced between the separation column and the detector to remove the inhomogeneous phase. Separation chromatograms were successfully acquired after all the necessary changes of the system. Factors that would affect the phase retention ratio were investigated in order to understand the separation capacity and resolution of this innovative technique. Separation of a mixture of acetophenone and benzophenone was conducted at various experimental conditions. A promising number of theoretical plates was obtained after preliminary endeavor. A more comprehensive examination is currently underway in our laboratory to optimize the system.