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

Abstract

The chemical character, geometry, and architecture of chemically formed surface layers determine interactions between stationary phase, analyte, and mobile phase, and therefore the retention mechanisms (partitioning, adsorption, ion exchange, steric exclusion) of separated analytes. These interactions also depend on the structure and chemical character of the solutes and the composition of the mobile phase. High-molecular-weight fullerenes (C60 and C70) and water-soluble selenium-containing peptides (833 and 2607 Da) were used for the evaluation of laboratory-prepared octadecyl stationary phases with high and low coverage density before and after end-capping. The aim of this work was to study differences in surface coverage density and homogeneity and conformational changes of chemically bonded moieties and the influence of these parameters on the separation of mixtures of selenopeptides and fullerenes with significantly different molecular masses. A topographical model of the chemically modified stationary surface is presented.

Li@C60 complexes with amino acids: A theoretical analysis

“…This is further substantiated by other experimental studies that demonstrate the efficacy of functionalizing fullerenes with amino acid to increase their biological affinity [21][22][23][24]. Similar results reveal that synthesis of amino acid derivatives have been fabricated and seen to be soluble upon complexation [25][26][27]. Theoretical dynamics calculations [28] also show that the functionalization with peptides and amino acids can lead to fullerene-specific antibody interactions.…”

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

“…A high heat of adsorption of methanol on pure silica gel (56.07 J/g) and a reduced value for the lowest coverage density stationary phase (46.02 J/g) are observed. A more homogeneous and densely covered surface screens residual silanols more effectively and precludes penetration of solvent molecules among the chemically bonded moieties [16].…”

“…In RP-HPLC the hydrophobic oil-like phases tend to minimize their surface energy through a tendency to self-association [15][16][17][18]. The behavior of long-chain alkyls bonded to the silica gel is also influenced by the nature of the silica support.…”

“…The microcalorimetry measurement can help to define the conformation of chemically bonded phases and to predict the possibility of solvent penetration through the film of bonded ligands. The penetration and solvation depend strongly on the organization of bonded ligands on the silica gel surface [16,24,25]. The measured heat of adsorption is generated by both specific and nonspecific interactions.…”

Modeling solvation on the chemically modified silica surfaces

“…These hydrophobic oil-like phases tend to minimize their surface energy through a tendency to self-association [11][12][13][14]. The behavior of long-chain alkyl ligands is also influenced by the nature of the silica support.…”