title: Geometric characterization of straight-chain perfluorohexylpropyl adsorbents for high performance liquid chromatography.
abstract: The geometric characterization of porous adsorbents used as stationary phases in high performance liquid 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 silica 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.
authors.affiliation: Department of Chemistry and Pharmaceutical Sciences, University of Ferrara, via L. Borsari, 46, 44121 Ferrara, Italy. cvz@unife.it
authors.forename: Alberto
authors.initials: A
authors.lastname: Cavazzini
authors.forename: Luisa
authors.initials: L
authors.lastname: Pasti
authors.forename: Roberto
authors.initials: R
authors.lastname: Greco
authors.forename: Valentina
authors.initials: V
authors.lastname: Costa
authors.forename: Damiano
authors.initials: D
authors.lastname: Solera
authors.forename: Francesco
authors.initials: F
authors.lastname: Dondi
authors.forename: Nicola
authors.initials: N
authors.lastname: Marchetti
authors.forename: Aldo
authors.initials: A
authors.lastname: Laganà
authors.forename: Francesco
authors.initials: F
authors.lastname: Gasparrini
mesh_terms: D000327:Adsorption; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation*; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D010316:Particle Size; D016062:Porosity; D011312:Pressure; D012822:Silicon Dioxide / Q000737:chemistry; D017155:Wettability
chemical_list: D006845:Hydrocarbons, Fluorinated; D012822:Silicon Dioxide