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Adsorption of water from aqueous acetonitrile on silica-based stationary phases in aqueous normal-phase liquid chromatography
Authors: Soukup Jan | Jandera Pavel
Year: 2014
Type of publication: článek v odborném periodiku
Name of source: Journal of Chromatography A
Publisher name: Elsevier Science BV
Place: Amsterdam
Page from-to: 102-111
Titles:
Language Name Abstract Keywords
cze Adsorpce vody z vodného acetonitrilu na stacionionárních fázích založených na silikagelu v kapalinové chromatografii v normální fázi s vodně organickou mobilní fází Zbytková adsorpce vody z vodného acetonitrilu byla studována na 16 stacionárních fázích metodou frontální analýzy a coulometrickou titrací dle Karl-Fischera. Stacionární fáze zahrnovaly silikagel a modifikovaný silikagel s různými polaritami, oktadecyl, cholesterol, fenyl, nitril, pentafluorfenylpropyl, diol atd. Testoval se jak plně porézní materiál tak i povrchově porézní materiály. Preferenční adsorpce může být popsána Langmuirovou isothermou. Adsorpce vody silně závisí na polaritě a typu kolony. Méně, než jedna mono-molekulární vrstva vody byla adsorbována na kolonách založených na hydridovém silikagelu, kolonách Ascentis express F5 a Ascentis Express CN při saturační kapacitě kolony. Kolony s vázanými hydroxylovými a diolovými ligandy vykazují silnější adsorpci vody než čistý silikagel. Nejvíce se pak voda adsorbuje na zwitteriontových stacionárních fázích. Adsorpce vody;hydrofilní interakční chromatografie;HILIC stacionární fáze
eng Adsorption of water from aqueous acetonitrile on silica-based stationary phases in aqueous normal-phase liquid chromatography Excess adsorption of water from aqueous acetonitrile mobile phases was investigated on 16 stationary phases using the frontal analysis method and coulometric Karl–Fischer titration. The stationary phases include silica gel and silica-bonded phases with different polarities, octadecyl and cholesterol, phenyl, nitrile, pentafluorophenylpropyl, diol and zwitterionic sulfobetaine and phosphorylcholine ligands bonded on silica, hybrid organic-silica and hydrosilated matrices. Both fully porous and core-shell column types were included. Preferential uptake of water by the columns can be described by Langmuir isotherms. Even though a diffuse rather than a compact adsorbed discrete layer of water on the adsorbent surface can be formed because of the unlimited miscibility of water with acetonitrile, for convenience, the preferentially adsorbed water was expressed in terms of a hypothetical monomolecular water layer equivalent in the inner pores. The uptake of water strongly depends on the polarity and type of the column. Less than one monomolecular water layer equivalent was adsorbed on moderate polar silica hydride-based stationary phases, Ascentis Express F5 and Ascentis Express CN column at the saturation capacity, while on more polar stationary phases, several water layer equivalents were up-taken from the mobile phase. The strongest affinity to water was observed on the ZIC cHILIC stationary phases, where more than nine water layer equivalents were adsorbed onto its surface at its saturation capacity. Columns with bonded hydroxyl and diol ligands show stronger water adsorption in comparison to bare silica. Columns based on hydrosilated silica generally show significantly decreased water uptake in comparison to stationary phases bonded on ordinary silica. Significant correlations were found between the water uptake and the separation selectivity for compounds with strong polarity differences. Adsorption of water; Hydrophilic interaction chromatography; HILIC stationary phases

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