Abstract
Characterization of mesoporous adsorbents is traditionally performed in terms of the pore size distribution with bulk methods like physisorption and mercury intrusion. But their application relies on assumptions regarding the basic pore geometry. Although novel tools have enabled the quantitative interpretation of physisorption data for adsorbents having a well-defined pore structure the analysis of disordered mesoporosity still remains challenging. Here we show that small angle X-ray scattering (SAXS) combined with chord length distribution (CLD) analysis presents a precise and convenient approach to determine the structural properties of two-phase (solid-void) systems of mesopores. Characteristic wall (solid) and pore (void) sizes as well as surface areas are extracted without the need to assume a certain pore shape. The mesoporous structure of modern, commercially available fully porous and core-shell adsorbent particles is examined by SAXS/CLD analysis. Mean pore size and surface area are compared with results obtained from nitrogen physisorption data and show excellent agreement.
Highlights
Substantial progress has been made in the development of silica-based mesoporous particles for their application in high performance liquid chromatography (HPLC) over the last few years.[7,8] Worth mentioning is the reintroduction of core–shell particles[9] into the HPLC field and the advent of sub-2 mm fully porous particles.[10]
Since the mesopores of silica-based adsorbents provide the area of contact between analytes and the stationary phase their shape, size distribution, and accessibility are substantial for the diffusion properties, and because the total surface area is directly coupled with the pore size the accurate determination of the pore size distribution (PSD) is a prerequisite
The main purpose of this study was to demonstrate a correlation between two important quantitative parameters, as obtained with independent methods of pore size evaluation based on small angle X-ray scattering (SAXS) and nitrogen physisorption experiments
Summary
Substantial progress has been made in the development of silica-based mesoporous particles for their application in high performance liquid chromatography (HPLC) over the last few years.[7,8] Worth mentioning is the reintroduction of core–shell particles[9] into the HPLC field and the advent of sub-2 mm fully porous particles.[10]. The precise determination of these parameters is fundamental, if the mesopore space characteristics are correlated with the overall transport properties
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