Influence of the pore structure on the properties of silica based reversed phase packings for LC

Abstract

This paper describes the preparation and investigation of new, highly loaded, monomeric, silica based, reversed phase C18 and C30 packings. The influence of pore structure and endcapping on the properties of C18 and C30 packings is described. Using hydrothermal procedures, silicas with predictable pore size (9.3-25.5 nm) and surface area have been prepared. Silylation with long chain silanes substantially alters the pore structure of the silica: pore size and pore volume decrease. A new parameter, the volumetric surface coverage [mm3 x m(-2)] has been introduced. This parameter--calculated from on-column measured porosity data--indicates the pore volume portion occupied by the hydrocarbon chains. Endcapping does not significantly change the pore structure of the bonded phases. The reduced retentions (reduced with respect to unit area: [k/m2])--a good measure for comparing the retention behaviour of packings with different surface areas--are similar for most of the phases, demonstrating good accessibility of the pores for the solutes. Slightly lower retentions were found on the endcapped than on the non-endcapped phases for probes with dense pi-electron system (e.g. polyaromatic hydrocarbons) demonstrating the contribution of silanophilic interactions to the retention. The phases had been successfully used for various demanding separations, e.g. for the separation of flavonoids, carotenoids, resveratrol, and tocopherol isomers, fullerenes, and anions.

Fast, noninvasive and simultaneous near‐infrared spectroscopic characterisation of physicochemical stationary phases' properties: From silica particles towards monoliths

“…Silica is the main material used in all chromatographicbased separation procedures [22]. Therefore, the fast and noninvasive physicochemical characterisation is of highest interest.…”

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Infrared Spectroscopy: A Novel Tool for the Physicochemical Characterization of Particulate, Monolithic and Coated Stationary Phases

“…Silica is the main material used in all chromatographic based separation procedures [17]. A qualitative model based on principal component regression (PCR) allows clustering of materials with differences in particle size and/ or surface area, pore structure and derivatization in a threedimensional factor plot.…”

Use of fullerene‐, octadecyl‐, and triaconthyl silica for solid phase extraction of tryptic peptides obtained from unmodified and in vitro glycated human serum albumin and fibrinogen

“…For the SPE experiments C18 and C30 RP materials were synthetised from Kovasil silica gel according to the method first described in a previous paper [20]. The C60(fullerene)-derivatised silica particles (prepared, described and characterised first by the authors [19]) were made from three different silica gels with distinc-…”