Facile synthesis of zirconia-coated mesoporous silica particles by hydrothermal strategy under low potential of hydrogen conditions and functionalization with dodecylphosphonic acid for high-performance liquid chromatography

Dispersive solid-phase extraction based on zirconium metal-organic framework coupled with gas chromatography-mass spectrometry for determining sugar phosphates in biological samples

BACKGROUND

Sugar phosphates (SPx) play important role in the metabolism of the organism. SPx such as glycerate 3-phosphate, fructose 6-phosphate and glucose 6-phosphate in biological samples have the poor stability, similar structure and low abundance, which make their separation and detection more challenging.

METHOD

UiO-66-NH2 and ZrO2 coated SiO2(SBA-15) hard-core-shell adsorbents (UiO-66-NH2@SBA-15 and ZrO2@SBA-15) were synthesized, which were further used for dispersive solid-phase extraction for enriching the SPx in biological samples. The protocol was developed by UiO-66-NH2@SBA-15 and ZrO2@SBA-15 coupled with gas chromatography-mass spectrometry for the detection of trace SPx. The univariate experiment and response surface methodology were used to optimize the adsorption and desorption conditions.

RESULTS

The adsorbents showed excellent adsorption capacity and specificity towards SPx, which were proved by adsorption and selective experiments. Under the optimized conditions, there were good linearity within the range of 5.0-5000.0 ng mL-1, low limits of detection (0.001-1.0 ng mL-1), low limits of quantification (0.005-5.0 ng mL-1) and good precision (relative standard deviation less than 14.7 % for intra-day and inter-day). The satisfactory recoveries (89.1-113.8 %) and precision (0.5-14.6 %) were obtained when the sorbents were used to extract SPx from serum, saliva and cell samples. Moreover, UiO-66-NH2@SBA-15 was applied to the quantitative analysis of SPx from gastric cancer patients, because of a higher adsorption capacity (169.5-196.1 mg g-1).

CONCLUSIONS

UiO-66-NH2@SBA-15 showed great potential in the extraction of SPx in biological samples, which was beneficial to find out the metabolic change of SPx and explain the pathogenesis of the disease.

Simultaneous Determination of Posaconazole and Hemp Seed Oil in Nanomicelles through RP-HPLC via a Quality-by-Design Approach

The present study involves the development of a reverse-phase HPLC method employing the quality-by-design methodology for the estimation of posaconazole and hemp seed oil simultaneously in nanomicelles formulation. The successful separation of posaconazole and hemp seed oil was achieved together, and this is the first study to develop and quantify posaconazole and hemp seed oil nanomicelles with linoleic acid as the internal standard and developed a dual drug analytical method employing a quality-by-design approach. The study was performed on a Shimadzu Prominence-I LC-2030C 3D Plus HPLC system with a PDA detector and the Shim-pack Solar C8 column (250 mm × 4.6 mm × 5 μm) for analysis with a mobile phase ratio of methanol:water (80:20% v/v) maintaining the flow rate of 1.0 mL/min. The final wavelength was selected as 240 nm and the elution of hemp seed oil and posaconazole was obtained at 2.7 and 4.6 min, respectively, with a maximum run time of 8.0 min. Box Behnken design was employed to optimize the method, keeping the retention time, peak area, and theoretical plates as dependent variables, while the mobile phase composition, flow rate, and wavelengths were chosen as independent variables. Parameters such as specificity, accuracy, robustness, linearity, sensitivity, precision, ruggedness, and forced degradation study were performed to validate the method. The calibration curves of posaconazole and hemp seed oil were determined to be linear throughout the range for concentration. The suggested approach can be effectively utilized for estimating the content of drugs from their nanoformulation and proved suitable for both in vivo and in vitro research.

Synthesis and evaluation of ginsenosides imprinted polymer-based chromatographic stationary phase

The molecular imprinting technique has aroused great interest in preparing novel stationary phases, and the resulting materials named molecularly imprinted polymers coated silica packing materials exhibit good performance in separating diverse analytes based on their good characteristics (including high selectivity, simple synthesis, and good chemical stability). To date, mono-template is commonly used in synthesizing molecularly imprinted polymers-based stationary phases. The resulting materials always own the disadvantages of low column efficiency and restricted analytes, and the price of ginsenosides with high purity was very high. In this study, to overcome the weaknesses of molecularly imprinted polymers-based stationary phases mentioned above, the multi-templates (total saponins of folium ginseng) strategy was used to prepare ginsenosides imprinted polymer-based stationary phase. The resulting ginsenosides imprinted polymer-coated silica stationary phase has a good spherical shape and suitable pore structures. Additionally, the total saponins of folium ginseng were cheaper than other kinds of ginsenosides. Moreover, the ginsenosides imprinted polymer-coated silica stationary phase-packed column performed well in the separation of ginsenosides, nucleosides, and sulfonamides. The ginsenosides imprinted polymer-coated silica stationary phase possesses good reproducibility, repeatability, and stability for seven days. Therefore, a multi-templates strategy for synthesizing the ginsenosides imprinted polymer-coated silica stationary phase is considered in the future.

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.

Synthesis and evaluation of fosfomycin group end-capped packing materials for hydrophilic interaction liquid chromatography

Hydrophilic interaction liquid chromatography (HILIC) plays an important role in the analysis of compounds having high polarity. In this study, fosfomycin (F) was chosen as a new end-capping reagent, owing to the facile hydrolysis reaction of its epoxy group. Zirconia coated silica (ZrO₂/SiO₂) materials having good chemical and physical stability were prepared. D-glucose-6-phosphate (G) and D-fructose1,6-bisphosphate (FDP) were modified onto the inner and outer surfaces of the ZrO₂/SiO₂ microbeads. The new end-capping reagent (F) was then bonded onto the surface of the modified material through Lewis acid-base interactions. The properties (morphology, Zr content, pore size, pore volume, and carbon content) of the stationary phases (SPs) were characterized. Finally, the resulting end-capped SPs were employed to separate alkaloids and benzoic acids. Multiple interactions, including HILIC, electrostatic repulsion, ion exchange and hydrogen bonding, contributed to the retention of the analytes on the SPs. On the F-FDP-ZrO₂/SiO₂ column, a theoretical plate number of 31,700 plates/m and an asymmetry factor of 1.63 were achieved for berberine, exhibiting good chromatographic performance. Furthermore, the FDP-ZrO₂/SiO₂ column showed good acid-base stability and good potential for the analysis of benzoic acid in Sprite and ginsenoside separations. Thus, the results indicated the significant potential of using F as an end-capping reagent.

Improvement of the froth flotation of LiAlO2 and melilite solid solution via pre-functionalization

In this work froth flotation studies with LiAlO₂ (lithium-containing phase) and Melilite solid solution (gangue phase) are presented. The system was optimized with standard collectors and with compounds so far not applied as collectors. Furthermore, the principle of self-assembled monolayers was introduced to a froth flotation process for the first time resulting in excellent yields and selectivities.

Enhanced visible-light driven multi-photoredox Cr(VI) and p-cresol by Si and Zr interplay in fibrous silica-zirconia

Multiple contaminants including heavy metals and phenolic compounds are normally co-exist in wastewater, which caused the treatment process is rather complicated. Herein, the synergistic photoredox of Cr(VI) and p-cresol (pC) by innovative fibrous silica zirconia (FSZr) photocatalyst was reported. The high surface area of FSZr comprised of microspheres with a bicontinuous concentric lamella structure morphology consisted of silica, while its core consisted of ZrO₂ structure. The rearrangement of FSZr framework increased the crystallinity, formed Si-O-Zr bonds and narrowed the band gap of ZrO₂ for enhanced of photoredox of Cr(VI) and pC. Compared to the reaction, the photoredox efficiency of FSZr for removing Cr(VI) and pC in simultaneous system was found to be 96 % and 59 %, respectively which are higher than that in its single system owing to the efficient electron-hole charge separation. Phenolic compound with high degree of electron donating group gave beneficial effect to photoreduction of Cr(VI). Consequently, a proposed mechanism involving multi-photoredox pathway were proposed based on photoredox reaction and scavengers studies. FSZr sustained the simultaneous photoredox activities after five runs demonstrating its possibility to be use in the wastewater treatment of various pollutants.

One-pot hydrothermal cross-linking preparation of poly(vinylpyrrolidone) immobilized silica stationary phase for hydrophilic interaction chromatography

Hydrothermally cross-linked polyvinylpyrrolidone (PVP) immobilized SiO₂ stationary phase (CPVP-Sil) was prepared via a green and facile one-pot method which was demonstrated for hydrophilic interaction liquid chromatography (HILIC) as well as reverse phase chromatography(RP). A water or organic solvent-insoluble permanent CPVP immobilizing on the silica particle surface can be formed simply by dipping silica particles into PVP solution and low temperature hydrothermal treatment. The cross-linked PVP network coating on SiO₂ endow it ring lactam functional groups which exhibited excellent separation ability of polar compounds by a typical HILIC retention mechanism at higher organic solvent contents (>55% ACN) and additionally polyvinyl groups for separation of alkylbenzenes in RP mode(<25% ACN). A high column efficiency of about 7 × 10⁴ plates per meter was obtained for the test catechol compound. Remarkably, the CPVP-Sil packing materials showed good stability in acid (at pH 3.5) or basic (at pH 9.5) conditions, with 5400-fold column volumes and 3500-fold column volumes respectively.