title: Correlation of chromatographic performance with morphological features of organic polymer monoliths.
abstract: Monoliths are considered to be a low pressure alternative to particle packed columns for liquid chromatography (LC). However, the chromatographic performance of organic monoliths, in particular, has still not reached the level of particle packed columns. Since chromatographic performance can be attributed to morphological features of the monoliths, in-situ characterization of the monolith structure in three dimensions would provide valuable information that could be used to help improve performance. In this work, serial sectioning and imaging were performed with a dual-beam scanning electron microscope for reconstruction and quantitative characterization of poly(ethylene glycol) diacrylate (PEGDA) monoliths inside a capillary column. Chord lengths, homogeneity factors, porosities and tortuosities were calculated from three-dimensional (3D) reconstructions of two PEGDA monoliths. Chromatographic efficiency was better for the monolith with smaller mean chord length (i.e., 5.23μm), porosity (i.e., 0.49) and tortuosity (i.e., 1.50) compared to values of 5.90μm, 0.59 and 2.34, respectively, for the other monolithic column. Computational prediction of tortuosity (2.32) was found to be in agreement with the experimentally measured value (2.34) for the same column. The monoliths were found to have significant radial heterogeneity since the homogeneity factor decreased from 5.39 to 4.89 (from center to edge) along the column radius.
authors.affiliation: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA.
authors.forename: Pankaj
authors.initials: P
authors.lastname: Aggarwal
authors.affiliation: Jigabot, Provo, UT 84601, USA.
authors.forename: Vikas
authors.initials: V
authors.lastname: Asthana
authors.affiliation: Department of Statistics, Brigham Young University, Provo, UT 84602, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Lawson
authors.affiliation: Department of Statistics, Brigham Young University, Provo, UT 84602, USA.
authors.forename: H Dennis
authors.initials: HD
authors.lastname: Tolley
authors.affiliation: Department of Chemical Engineering, Brigham Young University, Provo, UT 84602, USA.
authors.forename: Dean R
authors.initials: DR
authors.lastname: Wheeler
authors.affiliation: Department of Electrical Engineering, Brigham Young University, Provo, UT 84602, USA.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Mazzeo
authors.affiliation: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA. Electronic address: milton_lee@byu.edu.
authors.forename: Milton L
authors.initials: ML
authors.lastname: Lee
mesh_terms: D002853:Chromatography, Liquid / Q000295:instrumentation / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D011092:Polyethylene Glycols / Q000737:chemistry*; D016062:Porosity
chemical_list: C437167:poly(ethylene glycol)diacrylate; D011092:Polyethylene Glycols
keywords: Capillary columns; Column performance; Liquid chromatography; Polymer monoliths; Scanning electron microscopy