The geometric characterization of porous adsorbents used as stationary phases in high performance liq- uid chromatography is a key aspect for the understanding and the description of retention mechanisms. Herein, we present a study aimed at describing the geometric characteristics of alkyl-perfluorinated sil- ica stationary phases by employing chromatographic and non-chromatographic techniques. This study shows that, under typical chromatographic conditions, the perfluorohexylpropyl straight chains grafted to the silica surface assume a compact arrangement. As perfluorinated stationary phases are highly hydrophobic, their wetting behavior in water was investigated. To this end, a novel approach based on tracer pulse chromatography with pure water as the mobile phase and deuterium oxide as the labeled marker was employed. Experimentally it was found that, unless a high back-pressure is applied, water is expelled by the pores of the adsorbent. On the other hand, wetting can be significantly improved if 5–10% (v/v) of organic modifier is added to the mobile phase. The practical consequences of limited wettability are discussed, in particular with reference to fluorous-SPE (F-SPE) applications.

Geometric characterization of straight-chain perfluorohexylpropyl adsorbents for high performance liquid chromatography

CAVAZZINI, Alberto;PASTI, Luisa;GRECO, Roberto;COSTA, Valentina;DONDI, Francesco;MARCHETTI, Nicola;
2013

Abstract

The geometric characterization of porous adsorbents used as stationary phases in high performance liq- uid chromatography is a key aspect for the understanding and the description of retention mechanisms. Herein, we present a study aimed at describing the geometric characteristics of alkyl-perfluorinated sil- ica stationary phases by employing chromatographic and non-chromatographic techniques. This study shows that, under typical chromatographic conditions, the perfluorohexylpropyl straight chains grafted to the silica surface assume a compact arrangement. As perfluorinated stationary phases are highly hydrophobic, their wetting behavior in water was investigated. To this end, a novel approach based on tracer pulse chromatography with pure water as the mobile phase and deuterium oxide as the labeled marker was employed. Experimentally it was found that, unless a high back-pressure is applied, water is expelled by the pores of the adsorbent. On the other hand, wetting can be significantly improved if 5–10% (v/v) of organic modifier is added to the mobile phase. The practical consequences of limited wettability are discussed, in particular with reference to fluorous-SPE (F-SPE) applications.
2013
Cavazzini, Alberto; Pasti, Luisa; Greco, Roberto; Costa, Valentina; D., Solera; Dondi, Francesco; Marchetti, Nicola; A., Laganà; F., Gasparrini
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/1821106
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