Development and Application of Improved Methods for Coupling NMR and Capillary Isotachophoresis

堪萨斯大学的Cynthia Larive教授得到了分析和表面化学项目的支持，该项目旨在结合微线圈核磁共振光谱开发毛细管等速渗透(CITP)。从纳升到微升检测体积的螺线管微线圈的发展，极大地提高了核磁共振检测的质量极限。最近，通过毛细管等速电泳法(CITP)用于样品浓缩和分析物分离，以及纳升微线圈核磁共振探针用于在线检测，这项技术得到了进一步的发展。这种新的方法显示出相当大的前景，可以作为一种分析大量有限样品的通用工具。这项研究将促进在线CITP-核磁共振仪器的发展，并探索该方法在化学分析中的应用。将开发和评估与核磁共振检测结合使用的电容耦合电导检测器。CITP的双电导和核磁共振检测的实现将促进这项技术的发展，因为它有助于使用信号平均来检测具有核磁共振的稀释物，并监测核磁共振透明的CITP条带。这项技术将作为一种工具，通过检查几种抗生素化合物作为简单混合物和在更复杂的样品基质中的存在，对大量有限样品的分析和结构阐明进行批判性评估。最后，该方法将被用来通过CITP分级作为pH和硼酸盐络合的函数以及一维和二维核磁共振实验来表征腐殖质的结构、化学和物理性质。这些实验将检查分馏材料的官能团组成，从而能够解释由CITP分隔的带的共同和独特的结构元素。新的测量技术的发展促进了人们对许多复杂化学现象的理解。在环境化学领域尤其如此，科学家们面临着分析含有低浓度物种的非常复杂的样品的问题。拟议的实验将开发新的分析方法，使复杂样品中低浓度分子的核磁共振表征成为可能。核磁共振是一种信息量最大的化学分析方法，能够揭示分子结构的微小细节。最初的实验将集中在相对简单的抗生素样本、由于在大规模农业中广泛使用而具有环境意义的化合物，以及与抗生素耐药性发展相关的问题。此外，还将利用CITP-核磁共振技术研究一类环境重要的化合物--腐植酸类物质(腐植酸和黄腐酸)。腐殖质对环境具有重要意义，因为它们影响有机污染物和有毒金属离子的生物可利用性和传输。这些天然存在的有机酸是由动植物物质在环境中分解形成的，形成了非常复杂的混合物，这使得测定分子结构信息变得非常困难。这些实验将促进对腐殖质化学的了解，并反过来增加对它们在环境中行为的理解。

Professor Cynthia Larive of the University of Kansas is supported by the Analytical and Surface Chemistry program for development of capillary isotachophoresis (cITP) in combination with microcoil NMR spectroscopy. The development of solenoidal microcoils with nanoliter to microliter detection volumes has greatly enhanced the mass limits of detection of nuclear magnetic resonance (NMR). Recently, this technology has been advanced further through the coupling of capillary isotachophoresis (cITP) for sample concentration and analyte separation with nanoliter microcoil NMR probes for on-line detection. This new methodology shows considerable promise as a versatile tool for the analysis of mass limited samples. The proposed research will advance the instrumentation for online cITP-NMR and explore the application of this methodology to chemical analysis. A capacitively coupled conductivity detector for use in conjunction with NMR detection will be developed and evaluated. The implementation of dual conductivity and NMR detection for cITP will advance this technology by facilitating the use of signal averaging to detect dilute analytes with NMR and monitor NMR transparent cITP bands. This technology will be critically evaluated as a tool for the analysis and structure elucidation of mass limited samples through the examination of several antibiotic compounds both as simple mixtures and in the presence of more complex sample matrices. Finally, this approach will be used to characterize the structure, chemical and physical properties of humic substances through cITP fractionation as a function of pH and borate complexation as well as with one and two-dimensional NMR experiments. These experiments will examine functional group composition of the fractionated materials allowing interpretation of both common and unique structural elements of the bands separated by cITP. The development of new measurement techniques has facilitated understanding of many complex chemical phenomena. This has been particularly true in the field of environmental chemistry, where scientists face the problem of analyzing very complex samples containing species at low concentrations. The proposed experiments will develop new analytical methods that will allow NMR characterization of molecules at low concentrations in complex samples. NMR is one of the most informative methods of chemical analysis, capable of revealing minute details of molecular structure. Initial experiments will focus on relatively simple samples of antibiotics, compounds of environmental interest due to their wide spread use in large scale agriculture and problems related to the development of antibiotic resistance. In addition, cITP-NMR technology will be used to study a class of environmentally important compounds, humic substances (humic and fulvic acids). Humic substances are environmentally important because they affect the bioavailability and transport of organic pollutants and toxic metal ions. These naturally occurring organic acids are formed in the environment by the breakdown of animal and plant material to form very complex mixtures, which makes the determination of molecular level structure information very difficult. These experiments will advance the knowledge of the chemistry of humic substances and in turn increase the understanding of their behavior in the environment.