The effects of chain length, embedded polar groups, pressure, and pore shape on structure and retention in reversed-phase liquid chromatography: molecular-level insights from Monte Carlo simulations.
Particle-based simulations using the configurational-bias and Gibbs ensemble Monte Carlo techniques are carried out to probe the effects of various chromatographic parameters on bonded-phase chain conformation, solvent penetration, and retention in reversed-phase liquid chromatography (RPLC). Specifically, we investigate the effects due to the length of the bonded-phase chains (C(18), C(8), and C(1)), the inclusion of embedded polar groups (amide and ether) near the base of the bonded-phase chains, the column pressure (1, 400, and 1000 atm), and the pore shape (planar slit pore versus cylindrical pore with a 60A diameter). These simulations utilize a bonded-phase coverage of 2.9 micromol/m(2)and a mobile phase containing methanol at a molfraction of 33% (about 50% by volume). The simulations show that chain length, embedded polar groups, and pore shape significantly alter structural and retentive properties of the model RPLC system, whereas the column pressure has a relatively small effect. The simulation results are extensively compared to retention measurements. A molecular view of the RPLC retention mechanism emerges that is more complex than can be inferred from thermodynamic measurements.
Rafferty
Jake L
JL
Department of Chemistry, University of Minnesota, Minneapolis, MN 55455-0431, USA.
Siepmann
J Ilja
JI
Schure
Mark R
MR
D000465:Algorithms; D000577:Amides / Q000737:chemistry; D002853:Chromatography, Liquid / Q000379:methods*; D003198:Computer Simulation; D004987:Ethers / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D009010:Monte Carlo Method; D016062:Porosity; D011312:Pressure; D012821:Silanes / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013499:Surface Properties
D000577:Amides; D004987:Ethers; D012821:Silanes; D012997:Solvents; C082343:silanol