Alkaloid purification using rosin-based polymer-bonded silica stationary phase in HPLC

Fabrication and evaluation of dodecyl imide maleopimaric acid glycidyl methacrylate ester modified silica with multiple retention mechanisms for reversed phase liquid chromatography

As green, less toxic, and abundant ligands with rich functional groups, natural products are widely used in synthesis of chromatographic stationary phases. In this work, dodecyl imide maleopimaric acid glycidyl methacrylate ester (C12-MPAGN) was prepared from maleopimaric acid through the imidization and ring-opening based esterification reaction. By using "thiol-ene" click chemistry, it was chemically bonded to the silica and (3-mercaptopropyl) trimethoxysilane (γ-MPS) was used as the coupling agent to obtain dodecyl imide maleopimaric acid glycidyl methacrylate ester bonded silica stationary phase (Sil-C12-MPAGN). Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopies (SEM), and elemental analysis (EA) were utilized to verify that the Sil-C12-MPAGN stationary phase was successfully prepared with C12-MPAGN immobilized on the silica surface. In order to evaluate the chromatographic performance and retention mechanisms of the Sil-C12-MPAGN column and compared with C18 column, a variety of compounds were used, including stander mixture of Tanaka, alkylbenzenes, polycyclic aromatic hydrocarbons (PAHs), phenols and flavonoids. Based on these multiple interactions, including hydrophobic, hydrogen-bonding, and π-π interactions, high selectivity and superior separation performance were demonstrated by the Sil-C12-MPAGN column for probe molecules what had previously been mentioned. In addition, the quantitative determination of paclitaxel content in Yew bark extract was conducted with this column, which was found that the concentration was 83.67 mg/L, respectively. In short, the present study proposes a new strategy for introducing rosin to liquid chromatography with high selectivity and separation performance.

Removing Calcium Ions from Remelt Syrup with Rosin-Based Macroporous Cationic Resin

Mineral ions (mainly calcium ions) from sugarcane juice can be trapped inside the heating tubes of evaporators and vacuum boiling pans, and calcium ions are precipitated. Consequently, sugar productivity and yield are negatively affected. Calcium ions can be removed from sugarcane juice using adsorption. This paper described the experimental condition for the batch adsorption performance of rosin-based macroporous cationic resins (RMCRs) for calcium ions. The kinetics of adsorption was defined by the pseudo-first-order model, and the isotherms of calcium ions followed the Freundlich isotherm model. The maximal monolayer adsorption capacity of calcium ions was 37.05 mg·g^-1 at a resin dosage of 4 g·L^-1, pH of 7.0, temperature of 75 °C, and contact time of 10 h. It appeared that the adsorption was spontaneous and endothermic based on the thermodynamic parameters. The removal rate of calcium ions in remelt syrup by RMCRs was 90.71%. Calcium ions were effectively removed from loaded RMCRs by 0.1 mol·L^-1 of HCl, and the RMCRs could be recycled. The dynamic saturated adsorption capacity of RMCRs for calcium ions in remelt syrup was 37.90 mg·g^-1. These results suggest that RMCRs are inexpensive and efficient adsorbents and have potential applications for removing calcium ions in remelt syrup.

Effect of phenyl numbers in polyphenyl ligand on retention properties of aromatic stationary phases

Aromatic phase, as one type of reversed-phase stationary phases, shows complementary selectivity to the n-alkyl counterparts especially for certain challenging separation tasks. However, effect of phenyl numbers in aromatic ligands on retention behaviors has rarely been addressed compared with the alkyl stationary phases. To illustrate the issue, a series of polyphenyl stationary phases were facially prepared via the coupling chemistry of isocyanate with amine, including aniline (π¹), 4-aminobiphenyl (π²), 4-amino-p-terphenyl (π³) and [1,1':4',1'':4'',1'''-quaterphenyl]-4-amine (π⁴), respectively. The chromatographic behaviors of the new stationary phases as well as the traditional C18 were systematically compared in terms of retention mode, hydrophobic and aromatic selectivity, shape selectivity and π-π interaction by various analytes, including alkylbenzenes, polycyclic aromatic hydrocarbons congeners and substituted benzenes with electron-withdrawing groups. Due to the homologous structure of four polyphenyl ligands, the hydrophobic selectivity, aromatic selectivity and shape selectivity of stationary phases increase with phenyl numbers in the bonded polyphenyl ligands, whereas the increment becomes insignificant from U-π³ to U-π⁴. This phenomenon is explained by the insertion degree of analytes in the polyphenyl ligand brushes. Compared with the homemade C18, the polyphenyl phases indicate insignificant changes of shape selectivity with temperature. Notably, the new polyphenyl phases demonstrate the great selective separation towards the electron-deficient compounds through the π-π interaction. These findings make up for the understanding of the retention behavior of aromatic stationary phases.

[Preparation of modified rosin bonded silica high performance liquid chromatographic stationary phase and separation of Panax notoginseng saponins]

The sanqi is the dried root of Panax notoginseng (Burk.) F. H. Chen. The main components responsible for the drug actions of sanqi are notoginsenoside R1, ginsenoside Rg1, ginsenoside Re, ginsenoside Rb1, and ginsenoside Rd, which account for about 80% of the saponin content in sanqi. It is widely used in the treatment of anemia, coronary heart disease, hypertension, stroke sequelae, and other diseases. However, sanqi has many chemical components with complex and similar structures, which are difficult to separate. In this study, alkylated silica gel bonded with hydrogenated rosin hydroxyethyl acrylate (HRHA) was prepared via mercapto-ene click chemistry. A new type of modified rosin-bonded silica stationary phase (SiO2@HRHA) for high performance liquid chromatography was prepared for the separation of five saponins (R1, Rg1, Re, Rb1, and Rd). It was characterized by thermogravimetric analysis, Fourier-transform infrared spectroscopy, specific surface area and microporous physical adsorption and elemental analysis. The results showed that SiO2@HRHA had a regular spherical shape with porous surfaces, along with a specific surface area of 308.55 m2/g and an average pore diameter of 6.78 nm. Performance evaluation of the column revealed that the SiO2@HRHA column showed typical reversed-phase chromatographic behavior with better flowability and reproducibility. Results of the Tanaka test showed that SiO2@HRHA column had good stereoselectivity and hydrogen bond capacity. Compared to other stationary phases, e. g. silica modified with acrylopimaric acid (16-hydroxyethyl-34-hydroxyethyl acrylate) ester (AAE) and dihydroterpineol (DTP), which were prepared in our laboratory at the same time, the SiO2@HRHA column demonstrated better resolution (Rs) for the separation of the five saponins under optimal chromatographic conditions. The Rs values for R1, Rg1, Re, Rb1, and Rd were 3.33, 3.54, 20.17 and 9.72, respectively on the SiO2@HRHA column. Rs between Rg1 and Re was also better than that obtained on a C18 column. Panax notoginseng saponins were separated on the SiO2@HRHA column using acetonitrile and water as the mobile phases at the flow rate of 1.0 mL/min at 25 ℃. The optimal UV detection wavelength was 203 nm. It was found that the five saponins could be separated better using the SiO2@HRHA column than the SiO2@AAE and SiO2@DTP columns. Because the ternary phenanthrene skeleton of the rosin group in SiO2@HRHA had structural similarity and good stereoselectivity to the polycyclic compounds (Panax notoginseng saponins). In addition, according to the hydrophobicity evaluation, the SiO2@HRHA column showed the best hydrophobicity among the three columns, which may be conducive to the separation of the five saponins. Thus, this study can provide a new avenue for the separation and purification of Panax notoginseng saponins from actual samples.

Development and evaluation of a hydrogenated rosin (β-acryloxyl ethyl) ester-bonded silica stationary phase for high-performance liquid chromatography separation of paclitaxel from yew bark

Paclitaxel (PTX) is a complex diterpenoid anticancer drug whose separation from yew biomass poses a significant challenge. In this study, a new stationary phase comprising hydrogenated rosin (β-acryloxyl ethyl) ester (HRE)-bonded silica (HRE@SiO₂) is developed to separate and purify PTX from crude yew-bark extract using high-performance liquid chromatography. In HRE@SiO₂, HRE molecules, which are functional ligands, are bonded to the surface of a silica gel matrix using a coupling agent, (3-mercaptopropyl)trimethoxysilane. The proposed HRE@SiO₂ stationary phase was characterized by Fourier-transform infrared spectroscopy, elemental analysis, thermogravimetric analysis, scanning electron microscopy, laser diffraction granulometry, and nitrogen gas adsorption. The HRE@SiO₂ column exhibited excellent chromatographic performance, satisfactory performance reproducibility, and typical reversed-phase chromatographic behavior. An HRE@SiO₂ column was used to separate PTX and its analogs, achieving resolutions exceeding 7.43 for consecutively eluted species. Stoichiometric displacement theory for retention (SDT-R), the van Deemter equation, and van 't Hoff plots were used to analyze the separation mechanism and properties of the HRE@SiO₂ column. The results showed that hydrophobic interactions determine the analyte retention and the separation of PTX and its analogs on an HRE@SiO₂ column is an exothermic process driven by enthalpy. Furthermore, an HRE@SiO₂ column was employed to separate and purify PTX from crude yew-bark extract, increasing PTX purity from 6% to 82%. The findings of this study provide insights for developing rosin-based stationary phases for the separation of natural products.

Separation of alkaloids and their analogs in HPLC using rosin-based polymer microspheres as stationary phases

Rosin-based polymer microspheres (RPMs) as stationary phases in HPLC, and an RPM chromatographic column show good performance.