Characterization of Molecular Adsorption Using Liquid Chromatography and Mass Spectrometry
Abstract: Molecular adsorption is a key feature in several disciplines of chemistry, covering as diverse fields as chromatographic separation to biomaterial development. This thesis aims at developing methods and techniques for the characterization of molecular adsorption at the liquid-solid interface. Two different experimental models were used, small molecular interaction characterization using liquid chromatography and complex protein adsorption on polymeric materials possible for biological sampling. Holistic approaches, where both detailed molecular interactions and identifications of trends, could improve the fundamental understanding of adsorption systems, were invariably part of the scientific process.The characterization of small molecular interactions on liquid chromatography stationary phases via adsorption isotherm determination used combined data from physical phase parameters i.e. carbon loading, linear-, and nonlinear-characterization methods. These experiments were conducted on high performance liquid chromatography systems, using both ordinary reversed phase stationary phases, and hybrid phases. The expansion of the improved elusion by characteristic point (ECP) for adsorption isotherm determination, led to that previous impossible isotherm types, having inflexion points, now could be determined by the method. It also reduced errors in isotherm parameters due to the elimination of inaccurate determined retention times where the mobile phase concentration was zero.The characterization of protein adsorption where performed in an unbiased way. Adsorbed proteins on different surfaces were identified using mass spectrometry (MS) and data dependent acquisition or a targeted method. Prior MS, an improved on surface enzymatic digestion (oSED) method was used to enable identification and quantitation of adsorbed protein originating from ventricular cerebrospinal fluid (vCSF). oSED was found to be able to experimentally determine large variations in protein adsorption characteristics between native and coated polycarbonate surfaces in contact with vCSF. The method was also confirmed being mechanistic in favor of enzymatic digestion of the proteins adsorbed on a surface, rather than a prior desorption into solution before digestion.An improvement of the overall understanding of adsorption systems was not only achieved with the oSED method as a promising tool for characterization of protein adsorption on arbitrary surfaces, but also the use of linear and nonlinear approaches in stationary phase characterization that strengthened drawn conclusions.
CLICK HERE TO DOWNLOAD THE WHOLE DISSERTATION. (in PDF format)