Synthesis, Physical Characterization, and Chromatographic Performance of 1.7 μm and 1.1 μm Superficially Porous Particles Packed in Capillary Columns for Liquid Chromatography
Public Deposited- Last Modified
- March 21, 2019
- Creator
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Blue, Laura E
- Affiliation: College of Arts and Sciences, Department of Chemistry
- Abstract
- The predicted advantages of superficially porous particles over totally porous particles are decreased eddy dispersion, longitudinal diffusion, and resistance to mass transfer contributions to the theoretical plate height. These potential advantages arise from the effect of the inherently narrow particle size distribution on column packing and reduced diffusion volume due to the thin porous layer. While superficially porous particles are commercially available, further improvements in performance are predicted by decreasing the particle diameter, increasing the pore diameter, and decreasing the porous layer thickness. Both 1.7 μm and 1.1 μm superficially porous particles with a ρ value greater than 0.83 have been synthesized using a layer-by-layer method tuned for production of smaller diameter particles of varying pore diameter. Example synthesis parameters include type of polyelectrolyte, drying method, and sintering temperature. Using the revised synthesis conditions, monodisperse, uniformly coated superficially porous particles were produced. Following synthesis, these particles were packed into 30 μm i.d. capillary columns and their chromatographic performance evaluated using electrochemical detection. Based on the initial studies, the column efficiency was not as good as predicted, but was similar to that for commercially available products. It is believed that the column packing process plays a critical role in the sub-par column performance. To determine if column performance could be predicted by solventparticle interactions, in-solution microscopy, sedimentation velocity, and dynamic light scattering of particles in various slurry solvents were investigated and compared to column performance. Aggregating slurry solvents and high slurry concentrations were found to produce columns with increased efficiency but still have not reached theoretical values. Due to the predicted advantages of superficially porous particles for slowly diffusing analytes, particles of varying pore diameter were synthesized by altering the diameter of the colloidal silica used to produce the porous layer. Particles with pores ranging from 87 Å to 248 Å were produced. The performance of these particles was assessed using small molecules, peptides, and proteins. The performance of the larger analytes by LC/MS was found to improve as the pore diameter was increased, but was less efficient than that found for 1.9 μm Acquity BEH.
- Date of publication
- August 2012
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- In Copyright
- Advisor
- Jorgenson, James
- Degree
- Doctor of Philosophy
- Degree granting institution
- University of North Carolina at Chapel Hill
- Graduation year
- 2012
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