Development of High Efficiency and New Selectivity Liquid Chromatographic Phases for the Separation of Ionic and Hydrophilic Analytes

• Author / Creator

  Wahab, Muhammad F

• Separation of low molecular weight ions and hydrophilic analytes is achieved by high performance ion chromatography (IC) and hydrophilic interaction liquid chromatography (HILIC). The goal of this thesis was three-fold: to increase the efficiency of IC separations by employing small particles; to develop new selectivity phases for HILIC; and to understand the factors that can lead to distorted peak shapes. Long columns packed with large polymeric particles (6.5-13 µm) still dominate IC. This work investigated 3 µm carbon clad zirconia to which benzene sulfonic acid was bonded using diazonium chemistry. A 5 cm agglomerated anion exchanger was developed by adsorbing polycationic latexes to the particle surface. The efficiencies achieved (~ 51,000 /m) were superior to those of commercial column (~ 22,500 /m). In addition to particle size, column packing process strongly affects the efficiency. Packing studies with sulfonated particles (4.4 µm) showed that dispersed slurries are desirable to avoid particle agglomeration. Dispersed suspensions exhibit shear thickening that can be overcome by heating the slurry during column packing. Near optimum (reduced plate height ~ 2) packing of agglomerated columns was achieved. These studies concluded that the colloidal and rheological aspects of microparticulates must be considered to optimize packing. A new class of HILIC phases was created by modification of porous graphitic carbon (PGC) using diazonium chemistry. The hydrophobic PGC surface was converted into a polar HILIC phase by attaching benzoic acid groups. This phase showed unusual selectivity, which was different from 35 stationary phases. The utility of the phase was demonstrated for separations of nucleotides, phenols, and carboxylic acids. Overloading a column reduces the separation efficiency and alters the peak shape from Gaussian peaks to fronted or tailed peak profiles. Studies with IC columns showed that if the eluent anion is more strongly retained than the analyte ion on an ion exchanger, the analyte peak is fronting. If the eluent is more weakly retained on the stationary phase, the analyte peak always tails under overload conditions. Overall, this work has enhanced the fundamental understanding in the column packing process and offered new materials for the separation of ionic and polar analytes.

• Subjects / Keywords

  • Carbon
  • Diazonium
  • Chromatography
  • Packing
  • Suspensions

• Graduation date

  Fall 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R37P8TM0Z

• 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.