Separation of Panax notoginseng saponins on modified rosin ester-bonded silica stationary phase and its mechanism

Determination of the phase ratio of a dehydroabietic-acid-bonded silica-gel chromatographic stationary phase and its effect on separation thermodynamics

Rosin-based chromatographic columns are widely used for separation purposes, but, to date, their phase ratios (Φ) have been imprecisely measured. This affects the understanding of their separation mechanism and the calculation of related thermodynamic parameters. In this study, a stationary phase was synthesized by bonding dehydroabietic acid (DA) to silica gel (Si-DO) and applied for reversed-phase liquid chromatography. The distribution coefficient (Kdm) of methyl dehydroabietate (MD), which has the same structure as the bonded phase of Si-DO, was used as a surrogate for the determination of the equilibrium coefficient (K) of Si-DO, and the Kdm values of MD in different mobile phases were measured and compared with the K values of Si-DO. It was found that the phase ratio of Si-DO varied with mobile phase composition and temperature, as shown by the Φ values: 0.039-0.122 for the methanol/water system and 0.051-0.116 for the acetonitrile/water system; in addition, the a indices were 0.552-0.757 and 0.564-0.674, respectively. The Kdm of MD was closer to the K of Si-DO than those of other surrogate models, including the octanol-water and octane-mobile phase partition coefficients. In addition, the thermodynamic parameters (ΔG°, ΔH°, and ΔS°) of n-alkylbenzenes on Si-DO were negative, indicating a spontaneous and enthalpy-driven separation process. Overall, the phase ratio of rosin-based columns is crucial for accurate thermodynamic analysis and interpretation of the separation mechanism. Finally, the MD surrogate model allows the estimation of phase ratio of Si-DO and other similar columns, providing a novel method for measuring the phase ratio of rosin-based columns and providing a validated concept and methodology for determining the phase ratios of HPLC columns.

Quaternary ammonium-functionalized rosin-derived resin for the high-performance capture of caramels: Experiments and quantum chemical theory simulations

Water contamination caused by discharge of spent washes containing colorants remains controversial. In this study, rosin-derived strongly basic macroporous anion-adsorption resin (RSBMAR) was designed as an advanced adsorbent for scavenging caramel, the most recalcitrant colorant in spent washes. Toxicity tests suggest that RSBMAR is environmentally friendly and hardly threatens aquatic organisms. RSBMAR exhibits outstanding caramel capture efficiency because of its rich target quaternary ammonium (-R4N+) and protonated tertiary amine (-R3NH+) groups, abundant porous structure, large specific surface area, excellent thermal stability, and good sphericity. The caramel adsorption capacity of RSBMAR was 165.86 mg/g and the decolorization efficiency reached 96.75%. After five cycles, the spent RSBMAR maintained a high decolorization rate, indicating excellent renewability. Multiple characterizations indicated that caramel capture was largely mediated by charge interaction between -R4N+/-R3NH+ (RSBMAR) and -RCOO-/-RCOOH (caramel), followed by H-bonds. Quantum chemical theory simulations, including electrostatic potential, local ionization energy, frontier molecular orbitals, and independent gradient model analyses, further visualized caramel capture mechanisms at atomic level. Hirshfeld surface analysis revealed that RSBMAR acts as both an H-bond donor and acceptor during caramel uptake. Dynamic adsorption was performed to treat real wastewater, laying the foundation for the industrial application of RSBMAR.