Mid-IR Detection for u-HPLC, CE and CEC

This project aims to develop novel techniques to achieve sensitive and robust mid-IR spectroscopic detection in capillary based separation systems such as micro high performance liquid chromatography (-HPLC), capillary electrophoresis (CE) and capillary electrochromatography (CEC) and to apply these techniques to slected fields of application in life science and process monitoring (glycoside analytics). In the first technique possibilities for on-column mid-IR detction will be investigated. The research activities will start by developing dedicated microstructured flow cells for FTIR microscopic detection as well as dedicated set- ups employing quantum cascade lasers (QCL) as novel, powerful mid-IR light sources. It is planned to develop set- ups which allow the simultaneous use of several QCLs. Special attention will be paid to the integration of flow cell and QCLs on-chip as well as to innovative approaches for intra-cavity laser spectroscopy. In this part of the project there will be an intensive co-operation with the group of Prof. Gornik (TU Vienna) which has substantial know- how in QCL technology and agreed to provide acess to the facilities required to carry out the planned developments. The second technique to be developed within this project focuses on off-line FTIR spectroscopic detection after solvent elimination. To achieve this we plan to use novel flow-through microdispenser technology available through our co-operation partner Prof. Laurell from Lund, Sweden. Using this technology small and well defined deposits can be achieved which guarantee highly sensitive mid-IR spectroscopic detection. In the final stage of the project both techniques will be applied to solve actual problems in the field of glycoside analytics focussing on the analysis of resveratrol and its glycosides in wine and on the analysis of steroids and their glycosides in phytopharmaca. Here we plan to cooperate with Prof. Lindner who has substantial know-how and expertise in capillary based separation systems using standard (UV and MS) detectors. Finally, we plan to combnine our newly developed techniques with MS detection and to make use of the complementary information to solve difficult analytical problems in the field of glycoside analytics.

The aim of this research project was to contribute to the development of new technologies for the analysis of complex samples consisting of a mixture of different substances like proteins, phenols or sugars. The initial motivation was to establish new types of direct molecular specific detectors in modern miniaturized separation systems. In such systems the sample is injected into a flowing stream which passes a capillary where the substances (analytes) are retarded until they sequentially pass a detector where they are measured and quantified. Within this project new ways for realizing mid-infrared spectroscopic detection in such capillary based separation systems have been developed. Mid-infrared spectroscopy provides direct molecular specific information on the substances under investigation. With this technique characteristic vibrations and rotations of molecules can be observed. The recorded spectra may thus be regarded as a fingerprint of the whole or part of the sample under investigation. In addition to the use of infrared spectrometers and infrared microscopes we also developed detection systems comprising a new generation of miniature infrared lasers (quantum cascade lasers). After these new detectors had been developed they were applied in chiral separations as well as in protein analysis where the unique advantage of direct molecular specific detection could be successfully exemplified. Complementary, the newly developed detectors also helped to gain experimental evidence for in depth understanding of the separation mechanism prevailing in advanced operational modes in such separation systems. The research carried out using quantum cascade lasers also conducted to the development of powerful chemical sensors. As an example a prototype for the measurement of carbon dioxide in different kinds of beverages may be mentioned. It is this kind of results which may have immediate application in process monitoring of today`s industries. A more fundamental aspect of our research resulted from measurement campaigns carried out at infrared beamlines at synchrotron sources where mid-IR microscopic studies had been planned. Using these light sources we could extend our research activities also toward the far infrared spectral region which has only scarcely been investigated before due to a lack of appropriate light sources. In the far infrared spectral region intermolecular interactions in liquids can be investigated. This is particularly true for so called hydrogen bonds, the type of interaction present between water molecules in aqueous solution. Whereas no distinct spectra of salts, sugars or proteins could be recorded we could measure their effect on the hydrogen bonding network of liquid water. The structure forming or disrupting effect for kosmotropes and chaotropes could experimentally observed. In a similar way also the way how water molecules do interact with ionic liquids (salts that are molten at room temperature) could be determined from these studies. For the first time experimental evidence for the existence of clusters consisting of two water molecules in ionic liquids could be found.