Maximizing the practical value and investigating the retention characteristics of a remodified first-generation monolith

This study illustrates a procedure for producing different high-performance liquid chromatography (HPLC) stationary phases, on demand, for silica monoliths. Two commercial first-generation analytical scale bare silica monoliths were subjected to a "remodification" process that involved the following: (1) coating of the silica through an in situ silylation procedure to bond ligands of choice to the surface, (2) periodic chromatographic characterization of the coated surface over 2,000 column volumes, and (3) removing the bonded ligands using a 0.1. M hydrochloric (HCl) acid wash, to regenerate the initial silica surface.This remodification protocol was repeated for three cycles to fabricate monoliths with selected functionalities. To test reproducibility, this study was conducted on two different commercial silica monoliths subjected to this treatment involving synthetic reactions with organo-silanes and subsequent stripping with acid washes. Both monoliths were functionalized with three different coatings, without significant degradation of the initial columns' silica infrastructure and excellent stability (tested up to 2,000 column volumes). One of the monoliths had measured theoretical plates per meter (. N/m) of 57,000. N/m for the original silica surface, 105,000. N/m for the first cyano coating, and 60,000. N/m for the third phenyl coating. The stationary phases prepared by remodification possessed similar selectivities to those synthesized from new silica monoliths. The results of the Tanaka test shows evidence of residual ligands of previous coatings. However, the methylene and phenyl selectivity proved to display the same characteristics as other modified monoliths of the same functionality, not subjected to the remodified process.