Retention characteristics of a new butylimidazolium-based stationary phase. Part II: anion exchange and partitioning

Abstract

A surface-confined ionic liquid (SCIL) and a commercial quaternary amine silica-based stationary phase were characterized employing the linear solvation energy relationship (LSER) method in binary methanol/water mobile phases. The retention properties of the stationary phases were evaluated in terms of intermolecular interactions between 28 test solutes and the stationary phases. The comparison reveals a difference in the hydrophobic and hydrogen bond acceptance interaction properties between the two phases. The anion exchange retention mechanism of the SCIL phase was demonstrated using nucleotides. The utility of the SCIL phase in predicting logk (IL/water) values by chromatographic methods is also discussed.

Development and evaluation of new imidazolium-based zwitterionic stationary phases for hydrophilic interaction chromatography

“…Following the potential the novel IL stationary phase presents, researchers have reported a number of imidazolium ILs modified silica-based stationary phases prepared by different methods [13][14][15][16][17][18][19]. Moreover, Stalcup et al conducted a lot of studies on the retention behavior of IL stationary phases by investigating their multi-modal interactions with solutes via linear solvation energy relationships [20][21][22][23][24]. All the studies showed that the imidazolium ILs-based HPLC stationary phases exhibited good retention behavior due to the potential to interact with solutes through multiple solvation interactions, including hydrophobic, electrostatic, hydrogen bonding, etc.…”

Characterization of a novel pyridinium bromide surface confined ionic liquid stationary phase for high-performance liquid chromatography under normal phase conditions via linear solvation energy relationships

“…The introduction of new reversed phase media reinforces this dominance [1]. Recently, stationary phases containing covalently bound surface confined ionic liquid (SCIL) groups have been reported in the literature [2,3,4,5,6]. Their ability to separate individual classes of compounds under reversed phase conditions, and the physical characterization of these SCIL phases have been the primary focus of these reports [3].…”

“…In this work, the retention mechanism of a novel pyridinium bromide stationary phase is investigated using linear solvation energy relationships (LSER) under normal phase conditions. Linear Solvation Energy Relationships (LSER) have been used extensively to elucidate retention mechanisms in reversed phase liquid chromatography [2,3,11,12]. In contrast, LSERbased characterization of normal phase chromatography is far less common.…”

“…The LSER methodology [13,14,15], relating retention of an analyte on a stationary phase (log k) to a linear relationship of fundamental solute descriptors (Abraham's solute descriptors) [11], usually takes the form of (1) Recently, a different nomenclature has been adopted for the solute descriptors to simplify the model expressions [12,16,17], where the revised LSER equation takes the form of (2) Specifically, R 2 or E represent the excess molar refraction, which reflects polarizability contributions from π-and n-electrons; π * 2 or S are the solute dipolarity/polarizability; Σα H 2 or A and Σβ H 2 or B are the overall solute hydrogen bond acidity and basicity, respectively, which scale as the hydrogen bonding propensity of a solute to surrounding solvent molecules; V 2 or V are McGowan's characteristic volume. The log k o term is thought to include the phase ratio of the chromatographic system [2,3]. It should be noted that both of the stated models, Equations 1 and 2, fundamentally describe retention based upon global free energy principles directly related to the intermolecular interactions that occur between an analyte and the stationary/mobile phase system.…”

“…For instance, in reversed phase chromatography, the vV term is loosely related to the hydrophobicity of the stationary phase [2,3]. However, in normal phase studies, in the absence of water, the vV accounts for the ability of the mobile phase to participate in dispersive interactions and the relative energy required to form a "hole" in either the mobile phase or the stationary phase for the analyte [18].…”