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Structure and performance of silica‐based monolithic HPLC columns
Author(s) -
Altmaier Stephan,
Cabrera Karin
Publication year - 2008
Publication title -
journal of separation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.72
H-Index - 102
eISSN - 1615-9314
pISSN - 1615-9306
DOI - 10.1002/jssc.200800213
Subject(s) - macropore , high performance liquid chromatography , monolithic hplc column , chromatography , yield (engineering) , materials science , homogeneity (statistics) , monolith , chemistry , polymer , analytical chemistry (journal) , composite material , organic chemistry , mesoporous material , statistics , mathematics , catalysis
Abstract Silica‐based monolithic columns were prepared for HPLC with systematic variations of the tetramethoxysilane (TMOS) and polyethylene oxide (PEO) content as reactants in a sol–gel process accompanied by phase separation. The resulting monoliths showed differences in the macropore and silica skeleton diameter as well as in the corresponding domain sizes (the sum of macropore and skeleton diameter). All monoliths were synthesized with a diameter of 4.6 mm and cladded with a suitable polyaryletheretherketone (PEEK) polymer in a standardized and optimized manner for the subsequent chromatographic evaluation of the resulting monolithic HPLC columns. The columns were tested under normal phase conditions using n ‐heptane/dioxane (95:5 v/v) as a mobile phase and 2‐nitroanisole as a test compound for the determination of separation efficiency and permeability. Two different sets of columns were prepared: the first one in which the amount of PEO was stepwise decreased to yield monoliths with identical macropore volumes and variations in the domain sizes. The second group of materials was synthesized adjusting both TMOS and PEO quantities to yield monolithic columns with identical macropore diameters of about 1.80 μm but different skeleton diameters and macropore volumes. The chromatographic results suggest that an increase in the column performance cannot be achieved by just arbitrarily decreasing the domain size of a given column. From a certain point of “downsizing” the monolithic structure a loss of structural homogeneity can be observed, which is apparently responsible for a lower chromatographic performance.