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Abstract
Advancing the separation of isomeric species remains a central challenge in analytical chemistry, particularly for biomolecules like carbohydrates and amino acids where stereochemistry can significantly impact biological function. This dissertation explores strategies that leverage hydrophilic interaction liquid chromatography coupled with ion mobility–mass spectrometry (HILIC-IM-MS) to improve the resolution of stereoisomers and enhance structural glycan characterization.In the first part, I focused on separating D- and L-monosaccharide isomers using chiral derivatization via reductive amination with amino acids. Tyrosine tagging, in particular, enabled clear ion mobility separation between enantiomers and epimers, revealing how structural variation near the derivatization site affects gas-phase resolution. I then applied a complementary approach to amino acids, derivatizing them with various carbohydrate tags—including mono- and trisaccharides—to improve IM-MS separation. The maltotriose tag proved most effective for resolving 14 out of 17 amino acid enantiomeric pairs and was also extended to peptides containing site-specific D-amino acid substitutions.
The second part of this work focused on improving structural elucidation of N-linked glycans using HILIC retention time modeling. I developed a linear regression model based on monosaccharide retention motifs, creating a retention time prediction tool applicable across neutral and zwitterionic HILIC stationary phases. The model demonstrated strong predictive power, even across changes in column chemistry and gradient conditions, offering a scalable framework for characterizing unknown glycans without relying solely on reference libraries.
Finally, I evaluated mass transfer resistance in HILIC using columns with different pore sizes and particle types. Using dextran ladders, I compared separation efficiency across fully and superficially porous particles and demonstrated that the 160 Å superficially porous column offered the best balance of resolution and band broadening. These results reinforced the importance of column design and the role of the water-enriched stationary phase in HILIC retention mechanisms.
Collectively, these studies present new analytical strategies that improve isomer separation and glycan characterization, providing useful tools for glycomics, metabolomics, and protein chemistry applications.