Method development for the determination of 24S‐hydroxycholesterol in human plasma without derivatization by high‐performance liquid chromatography with tandem mass spectrometry in atmospheric pressure chemical ionization mode

We developed a highly sensitive and specific high‐performance liquid chromatography with tandem mass spectrometry method with an atmospheric pressure chemical ionization interface to determine 24S‐hydroxycholesterol, a major metabolite of cholesterol formed by cytochrome P450 family 46A1, in human plasma without any derivatization step. Phosphate buffered saline including 1% Tween 80 was used as the surrogate matrix for preparation of calibration curves and quality control samples. The saponification process to convert esterified 24S‐hydroxycholesterol to free sterols was optimized, followed by liquid–liquid extraction using hexane. Chromatographic separation of 24S‐hydroxycholesterol from other isobaric endogenous oxysterols was successfully achieved with gradient mobile phase comprised of 0.1% propionic acid and acetonitrile using L‐column2 ODS (2 μm, 2.1 mm id × 150 mm). This assay was capable of determining 24S‐hydroxycholesterol in human plasma (200 μL) ranging from 1 to 100 ng/mL with acceptable intra‐ and inter‐day precision and accuracy. The potential risk of in vitro formation of 24S‐hydroxycholesterol by oxidation from endogenous cholesterol in human plasma was found to be negligible. The stability of 24S‐hydroxycholesterol in relevant solvents and human plasma was confirmed. This method was successfully applied to quantify the plasma concentrations of 24S‐hydroxycholesterol in male and female volunteers.     

Controllable Synthesis of Hexagonal WO3 Nanoplates for Efficient Visible‐Light‐Driven Photocatalytic Oxygen Production

Facilitating charge‐carrier separation and transfer is fundamentally important to improve the photocatalytic performance of semiconductor materials. Herein, two‐dimensional hexagonal WO₃ nanoplates were synthesized by a two‐step route: rapid evaporation and solid‐phase sintering. The as‐prepared WO₃ exhibits an enhanced activity of photocatalytic water oxidation compared to bulk monoclinic WO₃. The electron dynamics analysis reveals that a more efficient charge‐carrier separation in the former can be obtained, the origin of which can be attributed to an increased number of surface defects in hexagonal WO₃ nanoplates. This work not only presents a novel and simple method to produce two‐dimensional hexagonal WO₃ nanoplates, but also demonstrates that surface defects and two‐dimensional geometric structures can promote the charge separation, which may be extended to the design of other efficient photocatalysts.     

Activation of Cellulose Assisted by CO2 for the Preparation of a Superhydrophobic Nanocoating

There is increasing demand for superhydrophobic materials, which can be used for separating oil and water efficiently. To avoid secondary pollution, it is desirable to prepare such materials with green technology. Here, we present an environmentally benign method for fabricating superhydrophobic materials by using organic base based solvents in which cellulose can be dissolved and activated. The dissolved cellulose could be chemically modified with a silanization reagent, and the solvent could be recycled after CO₂ was removed. The obtained cellulose nanocoating exhibited excellent hydrophobic effects. By spraying it on filter paper (water contact angle (WCA)=165°) for oil and water separation, the separation efficiency of more than 95 % was achieved; ultrasonication of an ordinary sponge in its dispersion (WCA=163°), meant it could be used as an oil absorber. It can also absorb a certain amount of bisphenol A (BPA), with the concentration decreasing by 66 % from the original concentration (0.1 mm ). Besides the high separation efficiency, it is resistant to a wide range of pH solutions, which means that it could be used in harsh environments. More importantly, the process is cost‐effective, the solvent can be recycled, and the whole process is green. Thus, the activation method provides a green route for the preparation of other cellulose‐based materials.     

IrIII‐based Octahedral Metalloligands Derived Primitive Cubic Frameworks for Enhanced CO2/N2 Separation

We developed a metalloligand strategy to construct porous frameworks, viz. the combined use of Ir^III‐based octahedral metalloligands and the linear unit [Ni(cyclam)] easily afforded two isostructural complexes 1 and 2 with primitive cubic frameworks. Both complexes show good CO₂/N₂ separation property.     

Chiral separation of quinolones by liquid chromatography and capillary electrophoresis

The quinolones are derivatives of oxoquinolines and mostly known for their antibacterial and antiviral activities. Many quinolones are chiral compounds having asymmetric centers and important due to their enantioselective biological activities. In order to study the biological activities of quinolone enantiomers, to control the manufacturing of homochiral drugs and to prepare necessary quantities of pure enantiomers for preclinical or clinical trials, respective chiral separation methods are urgently needed. In this context, the present review discusses chromatographic and electrophoretic methods for the enantioseparation of chiral quinolones and provides some useful information on their physical and pharmaceutical properties. The drawbacks of currently used techniques are revealed and ways to overcome them are outlined. Moreover, recommendations for an optimal choice of a separation protocol are given.     

A novel in situ strategy for the preparation of a β‐cyclodextrin/polydopamine‐coated capillary column for capillary electrochromatography enantioseparations

Inspired by the chiral recognition ability of β‐cyclodextrin and the natural adhesive properties of polydopamine under alkaline conditions, in this study, a rapid and in situ modification strategy was developed to fabricate β‐cyclodextrin/polydopamine composite material coated‐capillary columns for open tubular capillary electrochromatography. The results of scanning electron microscopy, FTIR spectroscopy, streaming potential, and electro‐osmotic flow studies indicated that β‐cyclodextrin/polydopamine was successfully fixed on the inner wall of the capillary column. This coating can be achieved within 1 h affording a greatly reduced capillary preparation time. The performance of the β‐cyclodextrin/polydopamine‐coated capillary was validated by the analysis of seven pairs of chiral analytes, namely epinephrine, norepinephrine, isoprenaline, terbutaline, verapamil, tryptophane, carvedilol. Good enantioseparation efficiencies were achieved for all. For three consecutive runs, the relative standard deviations for the migration times of the analytes for intraday, interday, and column‐to‐column repeatability were in the range of 0.41–1.74, 1.03–4.18, and 1.66–8.24%, respectively. Moreover, the separation efficiency of the β‐cyclodextrin/polydopamine‐coated capillary column did not decrease obviously over 90 runs. The strategy should also be feasible to introduce and immobilize other chiral selectors on the inner walls surface of capillary columns.     

Chiral separation of novel diazenes on a polysaccharide‐based stationary phase in the reversed‐phase mode

Chiral high‐performance liquid chromatography separation of two recently synthesized liquid crystalline materials C1 and C2 was studied in the reversed‐phase mode. Both materials have an azo‐moiety and one chiral center in their molecular structures. They were available in racemic and pure S forms. For the enantiomeric separations, a Chiralpak AY‐RH stationary phase based on amylose tris(5‐chloro‐2‐methylphenylcarbamate) coated on 5 μm silica was used. The compounds were analyzed in both of their possible forms, the more thermodynamically stable E form and the labile Z form. The conditions and time scale of the UV‐induced E to Z transition were briefly evaluated. Under the optimized conditions, we were able to baseline separate S and R enantiomers of both of the studied materials not only in their E forms, but also in their Z forms. In comparison to the separation in the normal‐phase mode, which we have reported recently, the resolution in the reversed‐phase mode is significantly better. Interestingly, peak reversal was noticed for the S and R enantiomers when the separation was carried out with E versus Z forms of both compounds.     

Three‐dimensional printed magnetophoretic system for the continuous flow separation of avian influenza H5N1 viruses

As a result of the low concentration of avian influenza viruses in samples for routine screening, the separation and concentration of these viruses are vital for their sensitive detection. We present a novel three‐dimensional printed magnetophoretic system for the continuous flow separation of the viruses using aptamer‐modified magnetic nanoparticles, a magnetophoretic chip, a magnetic field, and a fluidic controller. The magnetic field was designed based on finite element magnetic simulation and developed using neodymium magnets with a maximum intensity of 0.65 T and a gradient of 32 T/m for dragging the nanoparticle–virus complexes. The magnetophoretic chip was designed by SOLIDWORKS and fabricated by a three‐dimensional printer with a magnetophoretic channel for the continuous flow separation of the viruses using phosphate‐buffered saline as carrier flow. The fluidic controller was developed using a microcontroller and peristaltic pumps to inject the carrier flow and the viruses. The trajectory of the virus–nanoparticle complexes was simulated using COMSOL for optimization of the carrier flow and the magnetic field, respectively. The results showed that the H5N1 viruses could be captured, separated, and concentrated using the proposed magnetophoretic system with the separation efficiency up to 88% in a continuous flow separation time of 2 min for a sample volume of 200 μL.     

Preparation of magnetic molecularly imprinted polymer nanoparticles by surface imprinting by a sol–gel process for the selective and rapid removal of di‐(2‐ethylhexyl) phthalate from aqueous solution

Magnetic molecularly imprinted polymer nanoparticles for di‐(2‐ethylhexyl) phthalate were synthesized by surface imprinting technology with a sol–gel process and used for the selective and rapid adsorption and removal of di‐(2‐ethylhexyl) phthalate from aqueous solution. The prepared magnetic molecularly imprinted polymer nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and vibrating sample magnetometry. The adsorption of di‐(2‐ethylhexyl) phthalate onto the magnetic molecularly imprinted polymer was spontaneous and endothermic. The adsorption equilibrium was achieved within 1 h, the maximum adsorption capacity was 30.7 mg/g, and the adsorption process could be well described by Langmuir isotherm model and pseudo‐second‐order kinetic model. The magnetic molecularly imprinted polymer displayed a good adsorption selectivity for di‐(2‐ethylhexyl) phthalate with respect to dibutyl phthalate and di‐n‐octyl phthalate. The reusability of magnetic molecularly imprinted polymer was demonstrated for at least eight repeated cycles without significant loss in adsorption capacity. The adsorption efficiencies of the magnetic molecularly imprinted polymer toward di‐(2‐ethylhexyl) phthalate in real water samples were in the range of 98–100%. These results indicated that the prepared adsorbent could be used as an efficient and cost‐effective material for the removal of di‐(2‐ethylhexyl) phthalate from environmental water samples.     

Construction of Renewable Superhydrophobic Surfaces via Thermally Induced Phase Separation and Mechanical Peeling

We report a simple preparation method of a renewable superhydrophobic surface by ther-mally induced phase separation (TIPS) and mechanical peeling. Porous polyvinylidene fluo-ride (PVDF) membranes with hierarchical structures were prepared by a TIPS process under different cooling conditions, which were confirmed by scanning electron microscopy and mer-cury intrusion porosimetry. After peeling off the top layer, rough structures with hundreds of nanometers to several microns were obtained. A digital microscopy determines that the surface roughness of peeled PVDF membranes is much higher than that of the original PVDF membrane, which is important to obtain the superhydrophobicity. Water contact angle and sliding angle measurements demonstrate that the peeled membrane surfaces display super-hydrophobicity with a high contact angle (152°) and a low sliding angle (7.2°). Moreover, the superhydrophobicity can be easily recovered for many times by a simple mechanical peel-ing, identical to the original superhydrophobicity. This simple preparation method is low cost, and suitable for large-scale industrialization, which may offer more opportunities for practical applications.