Mobile phase effects in reversed-phase liquid chromatography: A comparison of acetonitrile/water and methanol/water solvents as studied by molecular simulation

• Published in: Journal of Chromatography A Vol. 1218; no. 16; pp. 2203 - 2213
• Main Authors: Rafferty, Jake L., Siepmann, J. Ilja, Schure, Mark R.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 22-04-2011; Elsevier
• Subjects: Acetonitrile; Acetonitriles - chemistry; adsorption; alkanes; Analytical chemistry; Chains; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography, Reverse-Phase - methods; Exact sciences and technology; Liquid chromatography; Methanol; Methanol - chemistry; Methyl alcohol; Models, Molecular; Molecular structure; Organic modifier; Other chromatographic methods; Retention mechanism; Reversed-phase liquid chromatography; Silanes - chemistry; Simulation; solutes; Solvents; Solvents - chemistry; Stationary phase structure; Surface chemistry; surface interactions; Thermodynamics; Water - chemistry; Simulation; Acetonitrile; Stationary phase structure; Reversed-phase liquid chromatography; Retention mechanism; Organic modifier; Methanol; Phase composition; Chromatographic retention; HPLC chromatography; Theoretical study; Mobile phase; Modeling; Mechanism; Reversed phase chromatography; Mixed solvent; Molecular model; Hydroorganic solvent; Mathematical model; Comparative study; Bonded stationary phase
• ISSN: 0021-9673; 1873-3778
• DOI: 10.1016/j.chroma.2011.02.012

Molecular simulations of water/acetonitrile and water/methanol mobile phases in contact with a C
18 stationary phase were carried out to examine the molecular-level effects of mobile phase composition on structure and retention in reversed-phase liquid chromatography. The simulations indicate that increases in the fraction of organic modifier increase the amount of solvent penetration into the stationary phase and that this intercalated solvent increases chain alignment. This effect is slightly more apparent for acetonitrile containing solvents. The retention mechanism of alkane solutes showed contributions from both partitioning and adsorption. Despite changes in chain structure and solvation, the molecular mechanism of retention for alkane solutes was not affected by solvent composition. The mechanism of retention for alcohol solutes was primarily adsorption at the interface between the mobile and stationary phase, but there were also contributions from interactions with surface silanols. The interaction between the solute and surface silanols become very important at high concentrations of acetonitrile.