Camptothecin-imprinted polymer microspheres with rosin-based cross-linker for separation of camptothecin from Camptotheca acuminata fruit

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.

Microwave extraction and molecular imprinted polymer isolation of bergenin applied to the dendrochronological chemical study of Peltophorum dubium

This study describes methodologies for extracting and isolating bergenin, a C-glucoside of 4-O-methylgallic acid found in some plants and it presents various in vitro and in vivo biological activities. Bergenin was previously obtained from the Pelthophorum dubim (Fabaceae) roots with a good yield. Conventional chromatographic procedures of the CHCl3 soluble fraction of the MeOH extract gave 3.62% of this glucoside. An HPLC/DAD method was also developed and validated for bergenin and its precursor, gallic acid quantifications. Microwave extractions with different solvents were tested to optimize the extraction of bergenin, varying the temperature and time. MAE (Microwave Assisted Extraction) was more efficient than conventional extraction procedures, giving a higher yield of bergenin per root mass (0.45% vs. 0.0839%). Molecularly imprinted polymer (MIP) and non-imprinted polymer (NIP) based on bergenin as the template molecule, methacrylic acid, and ethylene glycol dimethacrylate were synthesized and characterized by FTIR and SEM (Scanning Electron Microscopy). Bergenin adsorption experiments using MIP and NIP followed by molecular imprinted solid phase extraction (MISPE) showed that MIP had a higher selectivity for bergenin than NIP. A dendrochronological study using the proposed method for detection and quantification of gallic acid and bergenin in five P. dubium growth rings of a 31-year-old heartwood and in the phelloderm and barks indicated that bergenin was more abundant in the 11-14th growth rings of the heartwood and decreased from the heartwood to the barks.

Computational simulation-assisted design and experimental verification of molecularly imprinted polymers for selective extraction of chlorogenic acid

Chlorogenic acid (CGA) is an active ingredient in honeysuckle with a broad-spectrum of antibacterial activity, suppressing tumor growth and other pharmacological effects. However, it is susceptible to damage during traditional extraction and separation processes. Therefore, developing selective and efficient extraction methods of CGA is essential. Based on computational molecular simulations, a reliable and efficient molecularly imprinted polymers (MIPs) were successfully developed for selective extraction of CGA. MIPs and non-molecularly imprinted polymers (NIPs) were synthesized using a precipitation polymerization method, employing three different functional monomers: [methacrylic acid (MAA), 4-vinylpyridine (4-VP), and methyl methacrylate (MMA)], with CGA serving as the template molecule. To simulate the polymers and predict the optimal ratio between the template and functional monomer, the computational studies and adsorption performance experiments were carried out. The adsorption characteristics and thermal stability of polymers were evaluated by isothermal adsorption, adsorption kinetics, selective adsorption and thermogravimetric analysis, aiming to obtain the MIPs with specific recognition and selectivity for CGA. When the molar ratio of template CGA to functional monomer 4-VP was 1:8, the prepared MIPs was found to have the maximum adsorption capacity (14.85 mg g-1) and the highest imprinting factor (1.74) at the CGA concentration of 100 mg L-1. These results were consistent with those obtained by computational molecular simulation. This study not only provides good guidance for developing separation materials for extracting CGA from natural plants but also inspires the application of computer simulation and molecular docking techniques in the preparation of specific MIPs materials.

A review on solution- and vapor-responsive sensors for the detection of phthalates

Phthalic acid esters, largely referred to as phthalates, are today acknowledged as important pollutants used in the manufacture of polyvinyl chloride (PVC)-based plastics, whose use extends to almost every aspect of modern life. The risk of exposure to phthalates is particularly relevant as high concentrations are regularly found in drinking water, food-contact materials and medical devices, motivating an immense body of research devoted to methods for their detection in liquid samples. Conversely, phthalate vapors have only recently been acknowledged as potentially important atmospheric pollutants and as early fire indicators; additionally, deposition of these vapors can pose significant problems to the proper functioning of spacecraft and diverse on-board devices, leading to major space agencies recognizing the need of developing vapor-responsive phthalate sensors. In this manuscript we present a literature survey on solution- and vapor-responsive sensors and analytical assays for the detection of phthalates, providing a detailed analysis of a vast array of analytical data to offer a clear idea on the analytical performance (limits of detection and quantification, linear range) and advantages provided by each class of sensor covered in this review (electrochemical, optical and vapor-responsive) in the context of their potential real-life applications; the manuscript also gives detailed fundamental information on the various physicochemical responses exploited by these sensors and assays that could potentially be harnessed by new researchers entering the field.

Computer-aided design of molecularly imprinted polymer reinforced by double hybrid monomers for selective purification of hydroxycamptothecin

A kind of hydroxycamptothecin (HCPT) hybrid molecularly imprinted polymer (AT/MA-HMIPs) with high selectivity and hard silicon skeleton was successfully prepared based on double hybrid monomers. The relationship between templates and functional monomers was studied through computer molecular simulation and experiments. Three single-monomer molecularly imprinted polymers were prepared as controls. The Langmuir isotherm and pseudo-second-order kinetic models were found to fit well with the adsorption results. The maximum adsorption capacity was 18.79 mg/g, and equilibrium was reached within 20 min. Moreover, it shows excellent selectivity (imprinting factor is 10.73) and good recoverability (after 10 adsorption-desorption cycles, the adsorption capacity only decreases by 7.75%) for HCPT. The purity of HCPT can reach 80.86% after being put into a solid phase extraction column and used in an actual sample, and the yield was 61.43%. This study lays the fundament for the development of excellent HCPT molecularly imprinted composites.

Fabrication and application of molecularly imprinted polymer doped carbon dots coated silica stationary phase

Facing the difficulties in chromatographic separation of polar compounds, this investigation devotes to developing novel stationary phase. Molecularly imprinted polymers (MIPs) have aroused wide attention, owing to their outstanding selectivity, high stability, and low cost. In this work, a novel stationary phase based on carbon dots (CDs), MIP layer, and silica beads was synthesized to exploit high selectivity of MIPs, excellent physicochemical property of CDs, and outstanding chromatographic performances of silica microspheres simultaneously. The MIP doped CDs coated silica (MIP-CDs/SiO₂) stationary phase was systematically characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area measurement, and carbon elemental analysis. Furthermore, the chromatographic performance of the MIP-CDs/SiO₂ column was thoroughly assessed by using a wide variety of compounds (including nucleosides, sulfonamides, benzoic acids, and some other antibiotics). Meanwhile, the separation efficiency of the MIP-CDs/SiO₂ stationary phase was superior to other kinds of stationary phases (e.g. nonimprinted NIP-CDs/SiO₂, MIP/SiO₂, and C18-SiO₂). The results demonstrated that MIP-CDs/SiO₂ column exhibited best performance in terms of chromatographic separation. For all tested compounds, the resolution value was not less than 1.60, and the column efficiency of MIP-CDs/SiO₂ for thymidine was 22,740 plates/m. The results further indicate that the MIP-CDs/SiO₂ column can combine the good properties of MIP, CDs, with those of silica microbeads. Therefore, the developed MIP-CDs/SiO₂ stationary phase can be applied in the separation science and chromatography-based techniques.

Preparation, characterization, and separation mechanism of a dehydroabietic-acid-based shape-selective chromatographic stationary phase1

Chromatographic stationary phases with molecular-shape selectivity are advantageous for the separation and analysis of geometric isomers. Herein, dehydroabietic acid is bonded on the surface of silica microspheres via 3-glycidoxypropyltrimethoxysilane to form a monolayer dehydroabietic-acid stationary phase (Si-DOMM) with a racket-shaped structure. Various characterization techniques indicate that Si-DOMM is successfully prepared, and the separation performance of a Si-DOMM column is evaluated. The stationary phase has a low silanol activity and metal contamination and a high hydrophobicity and shape selectivity. The resolutions of lycopene, lutein, and capsaicin on the Si-DOMM column confirm that the stationary phase exhibits high shape selectivity. The elution order of n-alkyl benzene on the Si-DOMM column indicates its high hydrophobic selectivity and suggests that the separation is an enthalpy-driven process. Repeatability experiments reveal highly stable preparation processes of the stationary phase and column and indicate that the relative standard deviations of retention time, peak height, and peak area are less than 0.26%, 3.54%, and 3.48%, respectively. Density functional theory calculations using n-alkylbenzenes, polycyclic aromatic hydrocarbons, amines, and phenols as model solutes provide an intuitive and quantitative description of the multiple retention mechanisms. The Si-DOMM stationary phase exhibits superior retention and high selectivity for these compounds via multiple interactions. The bonding phase of the monolayer dehydroabietic acid stationary phase with a racket-shaped structure has a unique affinity for benzene, strong shape selectivity, and good separation performance for geometrical isomers with different molecular shapes.

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.

[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.

Chromatographic performance of zidovudine imprinted polymers coated silica stationary phases

Nowadays, molecularly imprinted polymers (MIPs) coated silica stationary phases (SPs) have aroused great attention, owing to their good properties of high selectivity, good stability, facile synthesis procedure and low cost. In this study, zidovudine imprinted polymers coated silica stationary phases (MIPs/SiO₂ SPs) were synthesized by surface imprinting technique using zidovudine as the template molecule, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linking agent, azobisisobutyronitrile as the initiator, and bare silica spheres (particle size, 5 μm; pore size, 20 nm) as substrates. In the process, reagents with low concentration were used to prepare thin layer of MIPs coating on the surface of silica microbeads. The properties of the materials were characterized by scanning electron microscope (SEM), fourier transform infrared spectrometer (FT-IR), carbon elemental analysis and N₂ adsorption-desorption experiment. The obtained SPs were packed into stainless steel columns (2.1 mm × 150 mm) via a slurry method. The prepared columns were applied for separation of nucleoside analogues with similar chemical structures and strong polarity. The retention mechanism of MIPs/SiO₂ SPs for nucleoside analogues was investigated carefully. And the chromatographic performances of the resulting MIPs based SPs were superior to those of the commercial SPs. Furthermore, the synthesized MIPs/SiO₂ SPs possessed great potentials in separation of ginsenosides. This investigation demonstrated that MIPs based SPs were successfully synthesized and provided a new approach to polar compounds separation and analysis.

Simple and Efficient Detection Approach of Quercetin from Biological Matrix by Novel Surface Imprinted Polymer Based Magnetic Halloysite Nanotubes Prepared by a Sol-Gel Method

Molecular imprinted polymers coated magnetic halloysite nanotubes (MHNTs-MIPs) were prepared through sol-gel method by using quercetin (Que), APTES and TEOS as template, monomer and cross-linker agent, respectively. The synthesized MHNTs-MIPs were characterized by fourier transform infrared, scanning electron microscope, transmission electron microscope, XRD and vibrating sample magnetometer. Various parameters influencing the binding capacity of the MHNTs-MIPs were investigated with the help of response surface methodology. Selectivity experiments showed that the MHNTs-MIPs exhibited the maximum selective rebinding to Que. Therefore, the MHNTs-MIPs was applied as a solid-phase extraction adsorbent for the extraction and preconcentration of quercetin and luteolin in serum and urine samples. The limits of detection for quercetin and luteolin range from 0.51 to 1.32 ng mL-1 in serum and from 0.23 to 1.05 ng mL-1 in urine, the recoveries are between 95.20 and 103.73% with the RSD less than 5.77%. While the recovery hardly decreased after several cycles. The designed MHNTs-MIP with high affinity, sensitivity and maximum selectivity toward Que in SPE might recommend a novel method for the extraction of flavonoids in other samples like 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.