Investigation of the concentration dependence of mass transfer coefficients in reversed-phase liquid chromatography

Abstract

In order to investigate the concentration dependence of mass transfer coefficients in RPLC, experimental breakthrough curves obtained by staircase frontal analysis (FA) were fitted to the simplified models such as multiplate (MP) model, equilibrium dispersive (ED) model, and transport model, and the sophisticated models such as lumped pore diffusion (POR) model and general rate (GR) model. The MP model was used to obtain the initial guesses of the parameters of the ED and the transport models. Then the best values were obtained by minimizing the differences between theoretical and experimental values with a nonlinear fitting procedure. The values of the parameters of the POR and the GR models can be calculated by using the expressions derived from the plate height equations, which was further validated by using the fitting method. It was found that the mass transfer coefficients would depend on the solute concentration. This can be ascribed to the surface diffusivity, which correlates with the concentration and is lumped into the mass transfer coefficients for both simplified and sophisticated models.

Simultaneous determination of two‐component isotherm parameters and lumped mass transfer coefficients in RPLC with the 0‐1 model‐inverse method

“…These data are contrary to , in which k f increases with increasing solute concentration. However, we obtained the result in accordance with . Hao et al drew their conclusion with the solute concentration >1.0 mg/mL.…”

“…However, we obtained the result in accordance with . Hao et al drew their conclusion with the solute concentration >1.0 mg/mL. As shown in Table , the different models can clearly lead to the visible difference for k f , depending on the solute concentration.…”

“…We first used the two-component competitive adsorption isotherm in the 0-1 model of the nonlinear transport chromatography. The simulated and experimental results indicated that the lumped mass transfer coefficients decrease as the solute concentration increases, which is contrary to references [28,29], but in agreement with reference [39]. This study indicated that the advantages of the 0-1 model-IM are the high calculation speed (<10 min for onecomponent systems or approximately 3 h for two-component systems using an ordinary computer) and the high accuracy (average errors of the peak areas are 0.178% for one component and −0.40% for two components) in simultaneously obtaining thermodynamic and kinetic parameters.…”

“…GR and POR) and their simplified multi-plate model. The current study of the concentration dependence of mass transfer coefficients seems very plausible [24,[28][29][30][31][32][33][34][35][36][37][38][39]. The representative references on concentration dependence of mass transfer coefficients with different models are summarized in Table 1.…”

“…They found that the errors in the predictions of the simulating profiles were most likely to occur with severe concentration changes. By assuming that the chromatographic process occurred in a series of theoretical plates, Hao et al proposed a multi‐plate model to investigate the concentration dependence of mass transfer coefficients with FA. They found that the mass transfer coefficient decreased with increasing solute concentration when the solute concentration was higher than approximately 1.0 mg/mL based on the sophisticated models (e.g.…”