Cation exchange characteristics of silica-based reversed-phase liquid chromatographic stationary phases

Abstract

Measurements of a reversed-phase column's capacity for H+ was found to be about 9 µ . Measurements of the displacement of H+ from the column by Na+ were consistent with an Ion-exchange process. Breakthrough capacities of alkali metals were In the 10-15 µ region In a mobile phase consisting of 55% methanol/45% water/0.1 N H3B03 (pH* 5.37). The breakthrough curves were typical of the behavior of a cation-exchange material. Long chain alkyl dimethylamines (protonated) and alkyl trlmethylammonlum Ions added to the mobile phase were more effective at reducing the column's Ion exchange capacity than the short chain analogues. Trlalkylammonium propanesulfonates, even though they show a marked affinity for the residual silica of the reversed-phase material In high methanol content mobile phases, did not appreciably alter the Ion-exchange capacities for K+.

Effect of coverage density and structure of chemically bonded silica stationary phases on the separation of compounds with various properties

“…The 29 Si solid-state NMR experiments were performed on an ASX Bruker spectrometer, model 300 (Rheinstetten, Germany) in the magic-angle spinning (MAS) mode ( Microcalorimetric measurements were performed using a laboratory-made microcalorimeter of the Tiana-Calve type. The temperature of measurement was 37 € 18C.…”

“…3 Results and discussion 29 Si CP/MAS NMR spectra (Fig. 1) provide important information about the structure of chemically bonded silica phases ( sponds to the monomeric structure with one-point ligand-silanol group bond [35].…”

“…Energetic differences on support surface and structural properties of the analyte influence which type of interaction and retention mechanism (adsorption, partition, ion exchange, or steric exclusions) will predominate. Residual, non-modified silanols can also react with the solvent molecules by specific and non-specific interactions [29]. In the case of hydro-organic eluents, silica groups are strongly hydrated by water molecules, resulting in retention caused by both hydrophobic and solvophobic impacts [30].…”

Study of solvent adsorption on chemically bonded stationary phases by microcalorimetry and liquid chromatography

“…The residual accessible silanols can also interact with the solvent and the analyte molecules by specific and nonspecific interactions [2,3]. In the case of a hydro-organic mobile phase, the silica is strongly hydrated by water molecules, resulting in retention caused by both hydrophilic and solvophobic impacts [4].…”

Evaluation of HPLC columns: A study on surface homogeneity of chemically bonded stationary phases

“…Thus, we obtain a packing with organic ligands located non-homogeneously. The remaining silanes can also react with the solvent molecules by specific and non-specific interactions [7]. In the case of hydro-organic eluents, silica groups are strongly hydrated by water molecules and that is why retention encompasses both hydrophobic and solvophobic interactions [8,9].…”