Retention mechanism assessment and method development for the analysis of iohexol and its related compounds in hydrophilic interaction liquid chromatography

Abstract

Hydrophilic interaction liquid chromatography (HILIC) has emerged in recent years as a valuable alternative to reversed-phase liquid chromatography in the analysis of polar compounds. Research in HILIC is divided into two directions: the assessment of the retention mechanism and retention behavior, and the development of HILIC methods. In this work, four polar neutral analytes (iohexol and its related compounds A, B, and C) were analyzed on two silica and two diol columns in HILIC mode with the aim to investigate thoroughly the retention mechanisms and retention behavior of polar neutral compounds on these four columns. The adsorption and partition contribution to the overall HILIC retention mechanism was investigated by fitting the retention data to linear (adsorption and partition) and nonlinear (mixed-retention and quadratic) theoretical models. On the other hand, the establishment of empirical second-order polynomial retention models on the basis of D-optimal design made possible the estimation of the simultaneous influence of several mobile-phase-related factors. Furthermore, these models were also used as the basis for the application of indirect modeling of the selectivity factor and a grid point search approach in order to achieve the optimal separation of analytes. After the optimization goals had been set, the grids were searched and the optimal conditions were identified. Finally, the optimized method was subjected to validation.

Modeling of HILIC retention behavior with theoretical models and new spline interpolation technique

“…Further on, the mobile‐phase composition had to be defined. Previous studies of our research group show that all of the mobile‐phase properties (pH, stronger eluent content, buffer type, and concentration) can affect HILIC retention, so they had to be carefully selected. Since olanzapine and all of its impurities are basic substances with p K a values all above 4.0, acidic pH had to be chosen for substances to exist in ionized forms, specifically as cations.…”

“…In accordance with current investigations in this field, our research group has already published several papers dealing with retention mechanisms of different analytes in the HILIC system . In this study, a detailed analysis of a mixture of olanzapine and its 8 impurities on 4 different HILIC columns was performed.…”

Recent applications of hydrophilic interaction liquid chromatography in pharmaceutical analysis

“…dipole-dipole interactions, hydrogen-bonding interaction of neutral polar species and electrostatic interactions of ionized species-both attractive and repulsive) are thought to be the major interactions in HILIC [19]. Diverse analytes exhibit different retention behaviors under distinguished SPs and chromatographic conditions, the actual retention mechanism depends on the MP composition, analyte properties (polarity and charge status), and functional groups of the SPs [20,21]. The specific types of interactions are typically probed by chromatographic methods with various chromatographic conditions (e.g.…”

Quality by Design approach in the development of hydrophilic interaction liquid chromatographic method for the analysis of iohexol and its impurities

“…In the literature, one paper involving the analysis of iohexol and related compounds A and B in iohexol solution for parenteral administration by LC-MS/MS method was found [18]. Our group has recently published the work suggesting the isocratic method for the simultaneous separation and quantification of iohexol and three related compounds A, B and C in iohexol solution for parenteral administration on diol stationary phase in HILIC mode [19]. However, the molecule of iohexol is present in two stereoisomeric forms: endo and exo, out of which exo isomer is dominant [20] and the suggested HILIC method did not provide the separation of endo and exo isomers of iohexol; both peaks eluted at the same retention time.…”