Silica Xerogel as a Continuous Column Support for High-Performance Liquid Chromatography

Abstract

A preliminary study of the chromatographic performance and permeability of a continuous silica xerogel column under reversed-phase HPLC conditions was performed. A porous chromatographic support was synthesized inside a 0.32 mm i.d. × 13 cm fused silica tube from potassium silicate solution and derivatized with dimethyloctadecylchlorosilane. The plate height at 0.01 cm/s (0.5 μL/min), near the apparent optimum linear velocity, was about 65 μm. The column efficiencies in terms of numbers of plates per meter were 5000 and 13 000 for ethyl benzoate (k = 0.8) and naphthalene (k = 2.0), respectively, at 0.5 μL/min. The major parameter affecting column efficiency was the heterogeneous morphology of the xerogel, modifications to which are expected to improve chromatographic performance. The column provided efficiencies comparable to those reported for continuous polymeric columns but less than that previously reported for a continuous silica column. Gradient elution mode was demonstrated with a mixture of polycyclic aromatic hydrocarbons. The column was highly permeable, exhibiting a linear dependence of pressure to flow rate and a back pressure of only 632 psi at 10 μL/min when a 95% aqueous mobile phase was used.

Capillary Electrochromatography on Monolithic Silica Columns

“…14 Continuous silica columns in a capillary have been reported for use in CEC as well as in HPLC. [15][16][17] The column efficiency of these monolithic columns was generally lower than that reported with columns packed with small silica particles. 18 Ishizuka and coworkers prepared a continuous silica gel from tetramethoxysilane using a sol-gel process in a fused-silica capillary.…”

Preparation of a monolithic column for weak cation exchange chromatography and its application in the separation of biopolymers

“…This monolithic column, being essentially the equivalent to a very large single cylindrical par-ticle, is prepared in a single step by a free-radical polymerization directly inside an empty stainless-steel tube acting as a mold. Examples of monoliths include polymeric matrices based on poly(glycidyl methacrylate-coethylene dimethacrylate) [13,14], poly(styrene-co-divinylbenzene) [15], poly(acrylamide-co-butyl methacrylate-co-N,N 9-methylenebisacrylamide) [16], as well as on silica [17,18]. At present, monolithic stationary phases have been widely used in the processes of bioseparation (chromatography and electrophoresis) [19,20], bioconversion (enzyme reactors) [21,22], as well as in other processes based on interphase mass distribution (e. g., solid phase peptide synthesis [23,24] and separation of plasmids and viruses [25,26]).…”

Polar stationary phases for capillary electrochromatography

“…Although Fields [55] already prepared the silica xerogel as a monolithic column support and demonstrated the feasibility in HPLC, no further data were reported in the CEC mode. Tanaka et al [56][57][58] pioneered the preparation of monolithic silica inside a capillary column using a sol-gel-transition process.…”