Eco-friendly high-throughput screening of cephalosporins impurities: Utilizing 2D-carbon microfiber fractionation system combined with quadrupole time of flight high-resolution mass spectrometer.

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Reversible polarity-switch of thin-layer chromatography by photo-induction with multi-regulation in spatial dimension.

Generally, thin-layer chromatography always undertakes the indispensable role in rapid screening and identification of specific compounds. Stationary phase is the core part of thin-layer chromatography with fixed property, which leading to the limitations of separation mode of only regulating the composition of mobile phase. This work was an attempt to fabricate the unique photosensitive thin-layer chromatography to make up the above major drawback. 4-[3-(Triethoxysilyl)propoxy]azobenzene (azo-PTES) was synthesized as photosensitive modifier to fabricate the photosensitive stationary phase, and the transformation of cis-trans structure of azo-PTES proceeds along with polarity difference under 365 nm and 473 nm irradiation. Based on this, the proposed photosensitive thin-layer chromatography shows the reversible switch of polarity of stationary phase by photoinduction, followed by the deserved reversible separation behavior. Furthermore, multi-regulation in spatial dimension was achieved based on the high freedom of spatial regulation of photoinduction, which brings about the integration of stationary phase with different polarity, just by photoinduction. The concept of photosensitive thin-layer chromatography provides new idea for improving separation efficiency and developing multi-dimensional thin-layer chromatography on the one plate.

Use of tandem carbon microfiber columns for on-line fractionation strategy of reducing ion suppression effects in electrospray ionization-mass spectrometry.

As we all know, the complexity and diversity of complex sample are confronting with challenge of high-sensitive mass spectrometry analysis, especially direct mass spectrometry. The work proposed a two-dimensional carbon microfiber fractionation (2DµCFs) system for the reduction of ion suppression effects in electrospray ionization mass spectrometry (ESI-MS). The 2DµCFs system can on-line fractionated the complex sample into strong-polar, medium-polar and weak-polar fractions for sequential MS analysis. Direct analysis brings about the strong ion suppression effect up to 85%, but the fractionated analysis of 2DµCFs system can distinctly reduce the ion suppression effect to less than 43%, even close to none. And the fractionated analysis not only decrease the number of analytes of direct analysis, but also narrows down the polarity range of analytes within the droplets of ESI, contributing to the homogeneous distribution to reduce the ion suppression effect. As an example, the 2DµCFs system coupled with tandem mass spectrometry (MS/MS) was applied for fractionated analysis of Radix Puerariae extract in 4.5 min. Compared with direct MS/MS, the 2DµCFs-MS/MS shows the lower ion suppression and the more ionic species (m/z). In addition, and most of ionic species detected by the 2DµCFs-MS/MS, are the same as those by HPLC MS/MS. Furthermore, the 2DµCFs-MS/MS exhibit the good analysis repeatability of real sample with the RSDs less than 10.32% (intra-day), 7.12% (inter-day) and 14.28% (inter-batch of CFs and ACFs). The carbon fibers (CFs) and active carbon fibers (ACFs) columns, as the key parts, are conducive to achieve on-line fractionation of compounds based on the difference of polarity. The 2DµCFs system has the merits of on-line, speediness, low-pressure and recycle. More importantly, such fast and high-throughput method is advantageous for comprehensive screening of complex samples in drug, clinical, environment and plant.

High-Resolution Micro-object Separation by Rotating Magnetic Chromatography.

The development of new technologies for the separation, selection, and isolation of microparticles such as rare target cells, circulating tumor cells, cancer stem cells, and immune cells has become increasingly important in the last few years. Microparticle separation technologies are usually applied to the analysis of disease-associated cells, but these procedures often face a cell separation problem that is often insufficient for single specific cell analyses. To overcome these limitations, a highly accurate size-based microparticle separation technique, herein called "rotating magnetic chromatography", is proposed in this work. Magnetic nanoparticles, placed in a microfluidic separation channel, are forced to move in well-defined trajectories by an external magnetic field, colliding with microparticles that are in this way separated on the basis of their dimensions with high accuracy and reproducibility. The method was optimized by using fluorescein isothiocyanate-modified polystyrene particles (chosen as a reference standard) and then applied to the analysis of cancer cells like Hep-3B and SK-Hep-1, allowing their fast and high-resolution chromatographic separation as a function of their dimensions. Due to its unmatched sub-micrometer cell separation capabilities, RMC can be considered a break-through technique that can unlock new perspectives in different scientific fields, that is, in medical oncology.

Circular Nonuniform Electric Field Gel Electrophoresis for the Separation and Concentration of Nanoparticles.

A circular nonuniform electric field strategy coupled with gel electrophoresis was proposed to control the precise separation and efficient concentration of nano- and microparticles. The circular nonuniform electric field has the feature of exponential increase in the electric field intensity along the radius, working with three functional zones of migration, acceleration, and concentration. The distribution form of electric field lines is regulated in functional zones to control the migration behaviors of particles for separation and concentration by altering the relative position of the ring electrode (outside) and rodlike electrode (inner). The circular nonuniform electric field promotes the target-type and high-precision separation of nanoparticles based on the difference in charge-to-size ratio. The concentration multiple of nanoparticles is also controlled randomly with the alternation of radius, taking advantage of vertical extrusion and concentric converging of the migration path. This work provides a brand new insight into the simultaneous separation and concentration of particles and is promising for developing a versatile tool for the separation and preparation of various samples instead of conventional methods.

Light-Driven Polarity Switching of the Chromatographic Stationary Phase with Photoreversibility.

Regrettably, conventional chromatographic columns have immutable polarity, resulting in requirements of at least two columns with polarity difference and sophisticated mechanical switching valves, which hinders the development of "micro-smart" multidimensional tandem chromatography. In this work, light-driven polarity switching was realized in a single capillary column based on the reversible trans-cis isomerization of 4-[3-(triethoxysilyl)propoxy]azobenzene as the stationary phase under light irradiation, with the change in dipole moment. As a result, the stationary phase offers precise and dynamic control of polarity based on the cis-trans azobenzene ratio, which depends on irradiation wavelength and time. Thus, the continuous adjustment of polarity enables diversified chromatographic separation modes, for example, step-polarity gradient and polarity-conversion separation modes, taking advantage of the superior freedom of polarity switching in time and spatial dimensions. The photosensitive column also shows good reproducibility of polarity photoreversibility and high separation efficiency. The present study might offer brand new insight into developing miniaturization and intellectualization of multidimensional chromatography via designing smart responsive switching valves or stationary phases, besides mechanical means.

A reciprocating magnetic field assisted on-line solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry determination of trace tetracyclines in water.

A reciprocating magnetic-field-assisted on-line solid-phase extraction (RMF-SPE) method coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for continuous enrichment of trace chemicals in water samples. Under the assist of the reciprocating magnetic field, carboxyl-modified magnetic nanoparticles (CMNPs) were applied to prepare microcolumn with even dispersion by periodical motion, instead of traditional compaction as extraction sorbents. When water sample passed through the extraction region, dynamic sorbents generates an advantage of countless contacts between sorbents and targets without blocking for high efficient extraction. In this study, the on-line RMF-SPE method was established and evaluated by determination of tetracyclines (TCs) from water samples as analysis models, including oxytetracycline, tetracycline, demeclocycline, metacycline, chlortetracycline, and doxycycline. Experimental conditions have been investigated such as flow rate, reciprocating speed, elution time, and so on. The method showed high relative recovery (95.4-111.1%) and good repeatability with RSD from 2.9 to 11.8% for the 200 mL water sample. The linearity range, limits of detection (LODs), and limits of quantification (LOQs) were 0.5-200 µg L-1 (chlortetracycline) and 0.1-200 µg L-1 (other TCs), 12.0-74.1 ng L-1, and 40.1-247 ng L-1, respectively. More importantly, the high enrichment factors in a range of 204 (chlortetracycline) to 276 (demeclocycline) indicate that a small amount of dynamic sorbents (only 10 mg) give full play to extraction attributing to the reciprocating movement, especially for trace analysis and continuous extraction, which is significant for water samples from sea, river and domestic waste.

Ex-situ and in-situ rapid and quantitative determination of benzene derivatives in seawater using nanoconfined liquid phase nanoextraction.

Benzene derivatives (BDs) constitute a class of environmental pollutants whose exposure poses a grave risk to human health. These compounds rapidly diffuse from the atmosphere to the marine ecosystem: for this reason, their monitoring in seawater is every day more compelling. In this work, nanoconfined liquid phase nanoextraction (NLPNE), a versatile extraction technique recently described, has been for the first time applied to the gas chromatographic mass spectrometry (GC/MS) analysis of BDs in seawater. Ex-situ and in-situ NLPNE procedures have been developed and optimized in terms of extraction capabilities, analysis time, precision, and accuracy. Compared to the traditional extraction procedures, based on solid-phase microextraction (SPME) and liquid-liquid extraction (LLE), the proposed NLPNE methods allowed a rapid on-site analysis of benzene compounds with low solvent consumption, higher enrichment factors, and improved automation grade. Determination coefficients ranging from 0.9929 to 0.9997 were obtained for all BDs in the range 0.10-500 ng mL-1 and 5.00-500 ng mL-1, for ex-situ and in-situ NLPNE, respectively. Ex-situ and in-situ limits of detection ranged from 0.2 to 7.6 ng mL-1 and 0.04-1.00 ng mL-1. Our results suggest that NLPNE coupled to GC-MS can be considered a powerful technique for high-throughput analyses of trace compounds in environmental, food and biological samples.

The solvent and zinc source dual-induced synthesis of a two dimensional zeolitic imidazolate framework with a farfalle-shape and its crystal transformation to zeolitic imidazolate framework-8.

Exploring new zeolitic imidazolate frameworks (ZIFs) with specific topologies and pore structures is important for extending applications and improving performances. In this work, a new farfalle-shaped ZIF with an ordered hierarchical structure (named ZIF-F) was easily built with zinc acetate and 2-methylimidazole (MeIm) in an aqueous system at room temperature. The synthesis mechanism of ZIF-F is a dual-induction interaction of a solvent and zinc source based on the synthesis protocol of ZIF-8. The prepared ZIF-F is a 3-5 µm dispersible particle constructed from numerous nanoplates with the same building units as ZIF-8. ZIF-F has a rich 4 nm inter-particle spacing with a 0.1074 cm3 g-1 total pore volume and exhibits high thermo- and solvent stability. It is worth noting that crystal transformation could occur from ZIF-F to ZIF-8 in methanol via the dissolution-recrystallization route. Regarding the adsorption of Congo red (CR), ZIF-F exhibits better adsorption capacity (182.82 mg g-1) than ZIF-8 (149.25 mg g-1) with 6 times higher adsorption rate than that of ZIF-8 because of the positive effect of its larger pore size and hierarchical structure.

Fast on-fiber derivatization and GC/MS analysis of phytohormones in wheat based on pencil-type coated carbon fibers.

New coated carbon fibers (CCFs) have been synthesized, characterized and used as solid phase microextraction (SPME) matrix for the analysis of phytohormones (jasmonic acid, indole-3-acetic acid, and abscisic acid) in wheat samples. The SPME device, realized inserting CCFs in a pencil-type device, when coupled with gas chromatography-mass spectrometry, provides in few steps high recovery values (79-112%), fast on-fiber derivatization (30 s), good method reproducibility (RSD < 20%), low detection limits (0.5-2.1 ng g-1). The pencil-type CCFs-SPME device was successfully employed for the determination of phytohormone in wheat samples, allowing simple and quick extraction/derivatization/injection processes. The proposed device can be then considered as a promising and functional tool for fast and reliable extraction and preconcentration of analytes from real samples, allowing a simple derivatization procedure and direct injection in the chromatographic instrumentation.

Magnetic separation coupled with high-performance liquid chromatography-mass spectrometry for rapid separation and determination of lignans in Schisandra chinensis.

Despite the strong antihepatotoxic, antioxidant, and antitumor properties of lignans from Schisandra chinensis, their applications in new drug development, bioscience and functional foods, etc. are limited because of their low abundance and complex coextractions. In this study, a magnetic separation method has been developed based on polyethylenimine-modified magnetic nanoparticles to rapidly and effectively separate and purify the lignans from S. chinensis crude extracts through cation-π interaction and electrostatic adsorption. The magnetic nanoparticles were characterized by transmission electron microscopy, vibrating sample magnetometry, Fourier transform infrared spectroscopy, and X-ray diffraction. Polyethylenimine-modified magnetic nanoparticles showed a spherical-shaped morphology and the average size was about 10 nm with superparamagnetism. Under the pH 7.4, polyethylenimine modified magnetic nanoparticles can remove a lot of coextracts. The range of detection limits and quantification limits was 0.27-0.34 and 0.89-1.13 ng/mL, respectively. Compared with other common methods, the magnetic separation method proposed in this study is much simpler and more effective through both strong cation-π interaction and electrostatic interaction.

Metal-organic framework UiO-66 coated stainless steel fiber for solid-phase microextraction of phenols in water samples.

Effective solid-phase microextraction (SPME) of polar phenols from water samples is usually difficult due to the strong interaction between polar phenols and aqueous matrix. Here, we report the fabrication of a metal-organic framework UiO-66 coated stainless steel fiber via physical adhesion for the SPME of polar phenols (phenol, o-cresol, p-cresol, 2,6-dimethylphenol, 2,4-dichlorophenol and 2,6-dichlorophenol) in water samples before gas chromatographic separation with flame ionic detection. Headspace SPME of 10mL sample solution with the fabricated UiO-66 coated fiber gave the enhancement factors of 160 (phenol) - 3769 (2,4-dichlorophenol), and the linear ranges of 1-1000µgL(-1) (2,6-dimethylphenol, 2,4-dichlorophenol and 2,6-dichlorophenol), 1-500µgL(-1) (o-cresol and p-cresol) and 5-500µgL(-1) (phenol). The detection limits ranged from 0.11µgL(-1) (2,6-dimethylphenol) to 1.23µgL(-1) (phenol). The precision (relative standard deviations, RSDs) for six replicate determinations of the analytes at 100µgL(-1) using a single UiO-66 coated fiber ranged from 2.8% to 6.2%. The fiber-to-fiber reproducibility (RSDs) for three parallel UiO-66 coated fibers varied from 5.9% to 10%. The recoveries obtained by spiking 5µgL(-1) of the phenols in the water samples ranged from 80% to 115%.