开放式电分离的机理研究

Separation technology lays the foundation for modern analytical chemistry, and its development is becoming fast, trace and sensitive. The emerging separation techniques and equipment have attracted great attentions in organic analysis field. Our previous study found an ambient electro-separation phenomenon; application of high voltages to a liquid thin-film sample on a conductive substrate had the capability to directly separate different types of compounds by mass-to-charge ratio, such as organic small molecules, biological macromolecules as well as surfactants. Fast and good separation performance could be achieved in sub-minute time. Even compounds with a molecular weight difference of 1 Da could be distinguished, close to the resolution of low resolution mass spectrometry (MS). However, the detailed mechanism has not yet been revealed. It is presumed that the compounds are arranged in the vertical direction according to the mass-to-charge ratio by the radial electric field component. The laminar flow phenomenon occurs in the liquid film by the longitudinal electric field component, and the laminar flow velocity represents to the maximum at a certain height from the substrate. These two aspects may be the main reasons for the occurrence of ambient electro-separation of compounds. The project aims to study the main factors affecting the separation of chemical compounds during the ambient separation process. The mechanism is supposed to be confirmed by experimental and theoretical model and both are combined to explore whether the compounds with different properties have the general characteristics of separation by mass-to-charge ratio. The implementation of this project will provide theoretical support for the development of emerging separation technologies with high efficiency and sensitivity and is expected to develop a low-cost separation instrument, similar to mass spectrometry.

化合物分离技术是现代分析化学的重要基础，其发展日趋快速、微量、灵敏。开发新型的分离技术和设备是有机分析的热点课题。我们前期研究发现了一种开放式电分离现象，直接将高压电场作用于导电基底上的液膜状样品，可以在亚分钟时间内将有机小分子、生物大分子和表面活性剂依质荷比顺序分离，甚至可分辨分子量相差1 Da的化合物，达到低分辨质谱的分辨率，然而其确切的分离机理尚不明确。推测化合物受径向电场分量作用在垂直方向按照质荷比规律排列；液膜受纵向电场分量作用发生电渗流层流现象，且距基底某一高度处层流速度最大；这两点是发生开放式电分离的主要原因。本项目拟采用改变影响化合物分离的主要因素为手段深入研究开放式电分离过程，通过实验来证实该机理，并构建理论模型来探索不同性质的化合物是否均具有按质荷比分离的普遍特性。本项目的实施将为开发新型的高效灵敏分离技术提供理论支持，并有望开发一种低成本的类质谱分离仪器。

化合物分离技术是现代分析化学的重要基础，本项目对固相基底上化合物的电分离现象及机理进行深入研究。首先选择具有不同物化性质化合物作为研究对象，使用基质填充毛细管电喷雾质谱作为稳定的研究平台，获取化合物物化性质、实验物理参数与开放式电分离的保留时间、出峰顺序之间相互关系的实验数据。通过不同的化合物性质参数和化合物保留时间之间的相关性统计分析，得出logD是影响保留时间的显著性因素，从而验证了色谱效应对电分离的影响。其次，化合物在5.5kV和4.0kV电压下保留时间的配对t检验(p<0.01)，表明化合物在不同电压下的保留时间存在显著性差异，从而验证了电场效应对电分离的影响。进一步发现电渗控制是通过电场影响化合物保留和分离的重要因素，电渗控制是通过溶剂添加剂调节电渗的大小和方向以及基底材料表面电荷来影响化合物的保留和分离。最后，结合色谱理论和电渗电泳理论，构建了化合物的保留因子与电场强度之间关系的数学模型，并通过化合物在不同电压下保留时间的变化规律验证了该数学模型。综上所述，化合物的电分离同时受到色谱效应和电场效应的影响。因此，通过调节色谱效应或电场效应可以实现化合物的分离优化，例如1% NH3•H2O添加剂通过电渗控制提高了高盐生物基质中L-色氨酸和L-脯氨的分离度。项目在应用研究中进一步开发了新型固相基底敞开式离子化技术-填充笔尖电喷雾质谱和超声溅射解吸质谱技术，可分别用于复杂生物液体中治疗药物的高灵敏分析和肿瘤组织的鉴定。本项目的实施不仅揭示了固相基底化合物的电分离机理，也开发了两种新型固体基底敞开式离子化技术。