Our favorite materials: Silica hydride stationary phases

Abstract

Geflügelte Elefanten: eine unglaubliche Vorstellung? Mindestens genauso unvorstellbar erschien es vor einigen Jahren, dass der massenspektrometrische Nachweis von Proteinen oder Polymeren gelingen könnte. Die Technik der Wahl – die Elektrospray‐Ionisation – gehört heute zur Standardausrüstung von Massenspektrometern.

Theory and Practice of UHPLC and UHPLC–MS

“…At full column saturation, the excess adsorbed water, V ex , fills up to 45.3% of the pore volume of normal silica-based columns but only 2.6%e5.5% of the pore volume of hydrosilated silica columns. Because of the low affinity of the hydrosilated silica material to water, saturation capacities are as low as 0.2%e0.4% water in the inner pore volume, which are achieved in mobile phases containing 3%e6% v/v water (for the hydrosilated bare silica or bonded C18 Bidentate columns), in agreement with the Pesek ANP model (Pesek and Matyska, 2009). This low water saturation capacity is similar to the long nonpolar alkyl chain (C30) columns.…”

“…The silica hydride material is less polar and shows less attraction for water (Pesek and Matyska, 2009) and improved pH stability in comparison to sil-gel columns; hence the authors suggested to denote the retention mechanism on hydrosilated silica as "aqueous normal-phase chromatography" rather than HILIC. However, HILIC separations are also essentially conducted in an NP system.…”

“…The sample partition between the bulk mobile phase and a submonomolecular layer of adsorbed water lacks a physical meaning. Rather, competition between the adsorbed water and polar solutes based on a NP adsorption mechanism (Pesek and Matyska, 2009) is more realistic. Hence, a low number of the adsorbed monomolecular equivalents, N w < 1, may be used to distinguish between aqueous normal phase (ANP) and traditional HILIC (Soukup and Jandera, 2014).…”

Temperature effects on solute retention for hydride‐based stationary phases

“…The same behavior was noted in a previous study using a column fabricated by a standard organosilanization protocol [15]. Therefore, as demonstrated in an earlier study of hydride type phases, they perform under most reversed-phase conditions like typical commercial C18 materials [16]. Figure 1B shows temperature studies on the lisinoprilrelated compounds but with a cholesterol stationary phase.…”

“…Hydride-based stationary phases have been shown to possess retention capabilities for polar compounds when the mobile phase contains high amounts of organic modifier, particularly acetonitrile [16]. These hydride materials have bonded to the surface a hydrophobic moiety like C18 and have reversed-phase properties such as those described above.…”