Comparative Study of Hydrocarbon, Fluorocarbon, and Aromatic Bonded RP-HPLC Stationary Phases by Linear Solvation Energy Relationships

Abstract

The retention properties of eight alkyl, aromatic and fluorinated reversed-HPLC bonded phases were characterized through the use of Linear Solvation Energy Relationships (LSERs). The stationary phases were investigated in a series of methanol-water mobile phases. LSER results show that solute molecular size under all conditions and hydrogen bond acceptor basicity are the two dominant retention controlling factors and that these two factors are linearly correlated when either different stationary phases at a fixed mobile phase composition or different mobile phase compositions at a fixed stationary phase are considered.The large variation in the dependence of retention on solute molecular volume as only the stationary phase is changed indicate that the dispersive interactions between nonpolar solutes and the stationary phase are quite significant relative to the energy of the mobile phase cavity formation process.Principal Component Analysis (PCA) results indicate that one PCA factor is required to explain the data when stationary phases of the same chemical nature (alkyl, aromatic and fluoroalkyl phases) are individually considered. However, three PCA factors are not quite sufficient to explain the whole data set for the three classes of stationary phases. In spite of this, the average standard deviation obtained by the use of these principal components factors are significantly smaller than the average standard deviation obtained by the LSER approach. In addition, selectivities predicted through the LSER equation are not in complete agreement with experimental results.These results show that the LSER model does not properly account for all molecular interactions involved in RP-HPLC. The failure could reside in the V 2 solute parameter used to account for both dispersive and cohesive interactions since "shape selectivity" predictions for a pair of structural isomers are very bad.

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 correlation matrix for the individual probe solutes (Table 2) indicates that there is a significant correlation (0.722) between the E and S molecular descriptor terms for the analytes used in this study [2]. This correlation has been noted previously and is expected because both terms reflect contributions to retention from the polarizability of the probe solutes [2,18]. In the present study, the chromatographic retention data obtained for the test solutes using hexane/2-propanol was subjected to a global multiple linear regression, including and individually omitting the eE and sS terms, to extract the LSER coefficients, using Equation 2.…”

“…In the LSER equations, the coefficients (e, s, b, a, v and log k o ), extracted from multiple linear regression analysis of the retention data, represent the difference of a specific interaction of the solutes between the stationary and mobile phases [18,19]. Overall, both the sign and the magnitude of the coefficients are critical in assessing whether the stationary or the mobile phase displays the greater interaction with the solute via a specific interaction mode.…”

“…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].…”

Quantitative structure‐retention relationships in reversed‐phase liquid chromatography using several stationary and mobile phases

“…To check the extent to which a QSRR equation describes all the interactions between the analytes and the chromatographic system, the residuals of the fit can be studied [34,35]. In Figure 1 the standardized residuals of all test compounds and all the columns are shown for selected mobile phase compositions.…”

Application of solvation model to prediction of the solute retention in liquid chromatography over a wide range of mobile-phase compositions

“…(1) describe the properties of the separation system; they are defined as the difference in the properties of the stationary and mobile phases [14][15][16][17][18][19][20][21][22]. Coefficient v is determined by the cohesive energy of the mobile and stationary phases and reflects the effect of dispersive interactions.…”