An Analysis of the Concentration Effects on Elution Volumes by Using the Preferential Solvation Parameter in Two SEC Packings

Abstract

Size exclusion chromatography (SEC) elution behavior of different solvent/polymer systems has been analyzed from chromatographic, thermodynamic, and hydrodynamic points of view in two organic column packings based on polystyrene/divinylbenzene (PS/DVB) copolymer, μ‐styragel and TSK‐Gel HHR. Although both packings present similar chromatographic properties, some differences arise when eluting the same systems. The values of the adsorption distribution coefficients, Kp, have been correlated with the preferential solvation coefficient, λ (see Figure), for both packings, showing that those systems with lower and negative λ values (denoting higher preferential solvation of the polymer by the gel packing) are those with Kp > 1. In addition, the main goal has been to make use of the λ values to adequately interpret the dependence of the elution volumes on injected polymer concentration. In this regard, the experimental concentration effects have been completely explained by taking into account not only the conventional hydrodynamic factors but also thermodynamic aspects such as the preferential solvation phenomenon.Plot of the preferential solvation coefficient, λ, as a function of the volume fraction of polymer (2), ϕ2, at three hydrodynamic volumes, Vh = 106 (○ •); 107 (□ ▪), and 108 (▵ ▴) mL · mol−1 for the system THF/PBD/PS (μ‐styragel: empty symbols; TSK‐Gel HHR (solid symbols).magnified imagePlot of the preferential solvation coefficient, λ, as a function of the volume fraction of polymer (2), ϕ2, at three hydrodynamic volumes, Vh = 106 (○ •); 107 (□ ▪), and 108 (▵ ▴) mL · mol−1 for the system THF/PBD/PS (μ‐styragel: empty symbols; TSK‐Gel HHR (solid symbols).

Separation Efficiency of Two SEC Packings: Comparison of Chromatographic, Thermodynamic, and Fractal Parameters

“…On the contrary, the highest swelling degree (measured by f 3 21 ) has been found for the TSK-Gel H HR . 3. In general, the fractal parameters (D f and L) are lower for the gel less swollen, that is, D f (XL gel) , D f (HR gel) and L (XL gel) , L (HR gel).…”

“…In previous work, [2,3] we have compared the new TSK-Gel H HR with the well known m styragel (from Waters), in order to analyze the specific features of the stationary phase that could explain some differences observed in the chromatographic behavior of polymer samples. In fact, it was shown that the crosslinking degree is a crucial parameter for high SEC separation efficiency, although it can also lead to nondesirable secondary effects, like adsorption of the polymeric solute onto the stationary phase.…”

The Fractal Approach to Secondary Mechanisms in SEC

“…0) since they are affected by different factors such as the injected solute concentration, the thermodynamic quality of the solvent, [47,48] viscous fingering, [49] and the preferential sorption. [50] among others. Significant deviations from a single UC curve are observed for different solvent-polymer systems in a given gel packing, or even for the same system when eluting in different commercial chromatographic supports.…”

Size‐Exclusion Chromatography in Single and Mixed Eluents: Effects of Sorption of Solvent and Polymer Solutes on Novel TSK‐Gel Super AW Columns

“…[9] (0.5, 0.2, and 0.1 g dL 21 ) and elution volumes determined by extrapolation to zero concentration, in order to avoid concentration effects.…”