Open-tubular columns for information-rich chromatography

This proposal addresses the development of new coated-capillary technology for liquid phase separations, namely liquid chromatography (LC) and capillary electrophoresis (CE), coupled to mass spectrometry, for use in the analytical determination of samples of biological importance which are often available in very small quantities only. The major drive for this research is that the ability of many analytical methods to provide adequate separation and sensitive, information-rich data is surpassed by the complexity of the sample and very small amount of sample material available for analysis. A new modification approach for development of coated capillary columns must be adaptable to narrow diameter columns, be reproducible, allow a wide range of chemical functionalities to be utilised and that the coating material itself promotes biocompatibility. New nanometer-sized monomeric precursors such as polyhedral oligomeric silsesquioxanes (POSS) with the basic structure (RSiO3/2) n (with n = 8, 10, 12) can be covalently bound to the wall of very narrow capillaries and used as the basis for new coated-capillary technology with extremely good stability. The first advantage of manufacturing coated capillary columns using POSS is the versatility in applying different functionalities to the covalently coated column using the same base structure, but provided with desirable chiral, hydrophobic, hydrophilic, or ionic moieties. This will be particularly valuable in developing capillary coatings for different analytical applications as a pre-optimised generic scaffold/surface allows `click` reactions to alter the functionality. This generic structure enables adjustment when different selectivity is required (in the case of LC) and/or enables reduction of secondary interactions between analyte and the capillary wall (primarily for CE). A second major strength of the POSS chemistry is that it can be used to develop both thick and thin coatings that would be suitable for LC and CE applications respectively. Importantly, the fundamental `click` chemistry enabling a wide range of chemical moieties to be attached remains the same for both applications. With this backbone chemistry it is possible to then address a wide range of analysis problems using two complementary separation approaches. Finally, the newly developed capillary coating technology will be utilised for the analysis of complex samples using hyphenated techniques (i.e. LC-MS and CE-MS). The dimensions and physicochemical properties of the new materials will be extremely favourable for highly efficient and sensitive analysis coupled to mass spectrometry detection.

This project was focused on miniaturising some aspects of chemical analysis, which can have a positive impact for minimizing resource consumption and providing better quality results for some types of chemical analysis. The type of chemical analysis considered can be broken into two aspects: firstly involving the separation of (chemical) components present within a mixture (sample). This separation step is important for focusing on individual components within more complex samples (e.g. determination of a pesticide in food). By separating the components using chemical principles, it becomes possible to accurately determine the identity and quantity of individual components present. The second major aspect of this work involves how these separated components can be subsequently identified. This is often achieved by determining the molecular mass of these components (molecules) following the separation step. There are well-known approaches that can achieve the goal of separation including techniques such as liquid chromatography and electrophoresis. Different chemical and physical principles are applied to separate components, but the general goal is the same. However, there are some practical difficulties encountered when using these techniques. For example, it is often extremely difficult to sufficiently separate all components within a sample as there may be 100s or even 1000s of components. For this reason, it is often an important task to optimise physical and chemical aspects of the technique in order to separate as many components as possible. Furthermore, it is often advantageous to miniaturise aspects of the separation where possible in order to reduce costs and minimise waste. Miniaturised separation approaches can also be essential when analysing samples that are only available in very small quantities. These ideas of miniaturising and optimising the separation of components go hand-in-hand with the second aspect of this project: increasing the amount of information gained from each analysis. Using mass spectrometry coupled with separation techniques to study separated components provides extremely valuable information about the identity of these molecules. Miniaturised separations are advantageous for this approach as the analysis is often more sensitive and chemical principles can be more easily implemented to study separated molecules yielding valuable information about the identities of these components. Practically speaking, this project focused on these two specific aspects of working toward these goals. Firstly, the development of new and versatile miniaturised materials was investigated in order to develop separation systems capable of separating many components from complex mixtures using minimal amounts of chemical resources. Secondly, the possibility of using physical and chemical principles in conjunction with miniaturised analysis for identifying separated components using mass spectrometry was studied. The work broadly demonstrates how these types of miniaturised systems can offer a more economic and resource-friendly approach to chemical analysis while still providing quality-information.