Development and Characterization of New Stationary Phases for Hydrophilic Interaction Liquid Chromatography

• Author / Creator

  Ibrahim, Mohammed Elsayed Abdelatif

• Hydrophilic interaction liquid chromatography (HILIC) has gained high popularity among separation scientists in the last two decades due to its ability to retain polar analytes. Many new HILIC stationary phases with different selectivities have appeared in the recent literature. Such developments require tools which can classify and compare the selectivity of these HILIC columns. In this thesis, straightforward and simple selectivity plots were constructed and used to classify HILIC stationary phases into bare silica, zwitterionic, neutral and amine-based phases.
  Silica monoliths show weak retention under HILIC conditions. In this thesis, the HILIC retention characteristics of silica monoliths were enhanced through surface modification with hydrophilic cationic latex nanoparticles. High efficiency (H ~ 25–110 µm) separations of carboxylic acids, amino acids and nucleotides were achieved. Due to their positive charge, the latex nanoparticles introduce anion exchange as another source of interaction. Consequently, these latex coated silica monoliths should exhibit mixed mode (HILIC/anion exchange) retention. Herein, the mixed mode retention of three different latex coated silica monoliths was studied. The AS9-SC latex coated silica monolith possessing the highest ion exchange capacity (44.1 µeq/column) separated six chaotropic and kosmotropic anions in less than 2.5 min.
  Silica is chemically unstable under extreme pH conditions. On the other hand, porous graphitic carbon (PGC) has high pH stability. Being a hydrophobic material, typically usage of PGC is restricted to reversed phase chromatography. In the presented thesis, a carbon-based HILIC stationary phase was developed as a new class of HILIC stationary phases via diazonium chemistry. The potential of this phase (carboxylate-PGC) as a HILIC phase was demonstrated by separation of carboxylic acids, phenols, amino acids and nucleotides. Carboxylate-PGC phase showed different selectivity than 35 columns.
  The efficiency of carbon-based phases is lower than silica due to slow mass transfer kinetics. Herein, we developed a hybrid phase comprising of 5 µm core-shell silica particles coated with 50 nm anionic carbon nanoparticles. This hybrid phase exhibited the unique selectivity of carbon and the high efficiency of core-shell silica particles. Fast and high efficiency HILIC separations of carboxylates and pharmaceuticals were achieved with efficiencies up to 85,000 plates/m.

• Subjects / Keywords

  • HPLC
  • HILIC
  • Liquid Chromatography

• Graduation date

  Spring 2014

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3WT1K

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.