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The nickel organic framework capped with polyvinylpyrrolidone was prepared and synergistically immobilized onto porous silica surface as the mixed-mode stationary phase for high-performance liquid chromatography. Here, polyvinylpyrrolidone firstly was chosen as functional molecules to change morphology and size of the metal organic framework. The silica microspheres were then modified by them via a simple bonding method rather than in-situ growth method with the aid of electrostatic interaction commonly used before. The stationary phase showed flexible selectivity for separation of both hydrophilic and hydrophobic compounds, especially for hydrophilic compounds such as carbohydrates, alkaloids and sulfonamides etc. The chromatographic behaviors were evaluated by investigating various factors, and a typical mixed-mode retention feature of the column was observed. The composites could be prepared repetitively, and relative standard deviations of retention time of objective compounds among different batches were less than 1.75%. It also showed excellent chromatographic reproducibility, stability and potentiality for application in real samples. In short, the composites can be used for a feasible option for analysis of multiple compounds as the mixed-mode stationary phase and it provides a general approach for preparing MOFs-based composites by changing morphology and size of MOFs. [Display omitted] • The polyvinylpyrrolidone was chosen as functional molecules to change morphology and size of the Ni-MOF. • The silica microspheres were modified by Ni-MOF capped with PVP via a simple bonding method. • The new composites showed flexible selectivity for separation of both hydrophilic and hydrophobic compounds. [ABSTRACT FROM AUTHOR]

l -Cysteine (L-Cys) and N-Isopropyl acrylamide (NIPAM)-modified silica spheres as a novel stationary phase for hydrophilic interaction liquid chromatography (HILIC) was produced firstly by cross-linking polymerization. Some characterizations in this article confirmed that the synthesis of Cys-Si-NIPAM is successful. Some polymer layers can be observed through transmission electron microscopy (TEM). In addition, through nitrogen adsorption porosity method, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and other characterization methods, we can find the significant changes after modify. It has good hydrophilic property and higher column effect than bare silica column, Si-Cys column and Si-NIPAM column under the same conditions. It has good separation effect for some hydrophilic analytes such as 5 nucleosides and nucleoside bases, 5 amino acids, 4 sulfonamide drugs and 10 saccharides. The effects including column temperature, pH and organic solvent content on chromatographic performance were studied, which proved that hydrophilic interactions can be simultaneously existed between the stationary phase and the analytes. In addition, reproducibility and efficiency of the Cys-Si-NIPAM column was also investigated, the results illustrated that the stationary phase have passable stability (the intraday RSDs 0.08–0.44%, n = 3 and the interday RSD 0.46–3.50%, n = 3) and ideal efficiency (plates per meter, ~45700 plates/m). In conclusion, the preparation process of this hydrophilic liquid chromatography stationary phase is not only simple, but also can meet the basic requirements for the separation of hydrophilic analytes. Image 1 • We combine the process of the coating and polymerization into one step in the preparation of stationary phase. • The method of solidified gel-coated silica spheres for hydrophilic liquid chromatography stationary phase was first proposed. • The separation mechanism of the column depends on the l-Cysteine and N-Isopropyl acrylamide used for surface modification. • Surface modification of silica spheres by cross-linking polymerization and thiol olefin click reaction proved to be feasible. [ABSTRACT FROM AUTHOR]

A class of novel, environmental friendly ionic liquids (ILs) were synthesized by on-fiber preparation strategy and modified on graphene oxide (GO)-coated stainless steel wire, which was used as a solid-phase microextraction (SPME) fiber for efficient enrichment of polycyclic aromatic hydrocarbons (PAHs) and phthalate esters (PAEs). Surface characteristic of the ILs and polymeric-ILs (PILs) fibers with the wave-structure were inspected by scanning electron microscope. The successfully synthesis of bis(trifluoromethanesulfonyl)imide (NTf 2 − )-based ILs were also characterized by energy dispersive spectrometer analysis. Through the chromatograms of the proposed two ILs (1-aminoethyl-3-methylimidazolium bromide (C 2 NH 2 MIm + Br − ), C 2 NH 2 MIm + NTf 2 − ) and two PILs (polymeric 1-vinyl-3-hexylimidazolium bromide (poly(VHIm + Br − )), poly(VHIm + NTf 2 − ))-GO-coated fibers for the extraction of analytes, NTf 2 − -based PIL demonstrated higher extraction capacity for hydrophobic compounds than other as-prepared ILs. Analytical performances of the proposed fibers were investigated under the optimized extraction and desorption conditions coupled with gas chromatography (GC). Compared with the poly(VHIm + Br − )-GO fiber, the poly(VHIm + NTf 2 − )-GO SPME fiber brought wider linear ranges for analytes with correlation coefficient in the range of 0.9852–0.9989 and lower limits of detection ranging from 0.015–0.025 μg L −1 . The obtained results indicated that the newly prepared PILs-GO coating was a feasible, selective and green microextraction medium, which could be suitable for extraction and determination of PAHs and PAEs in potatoes and food-wrap sample, respectively. [ABSTRACT FROM AUTHOR]

The functionalized non-conjugated organic network modified silica microspheres are proposed as the stationary phase of liquid chromatography, which can effectively avoid some defects of organic framework materials in liquid chromatography. Due to the co-existing of pyridine ring, carbonyl group, amide group and triazine ring in the non-conjugated flexible organic network on the silica surface, the developed mixed-mode stationary phase exhibits multiple interactions between the stationary phase and the analytes during the separation process. A variety of nucleoside bases, organic acids, antibiotics, pesticides, alkylbenzenes, polycyclic aromatic hydrocarbons and sulfonamides achieved ideal resolution and flexible selectivity in separation. Compared with the commercial chromatographic columns under their optimized chromatographic conditions, it shows better performance for the separation of complex analytes. The influence of chromatographic conditions on retention behavior indicates that the column's multiple retention mechanisms make it suitable for mixed-mode liquid chromatography. The stationary phase prepared by the new design strategy also has excellent chromatographic reproducibility, repeatability and stability with the intraday RSD of 0.09%–0.12% (n = 10) and the interday RSD of 0.37%–1.64% (n = 5) for the retention time. The separation results of actual samples also prove its potential in the analysis of complex samples. In short, we designed and prepared the non-conjugated flexible network modified silica stationary phase material for liquid chromatography that is different from organic framework materials. Its excellent separation ability shows that we have successfully reported a new kind of liquid chromatography packing with functional design and facile preparation method. [Display omitted] • An effective functional design strategy for LC stationary phase was proposed. • Baseline separation for multiple complex samples was got on Py-TAC-DMA@SiO 2 column. • The new column showed flexible selectivity for many different properties analytes. • The retention mechanism was discussed in detail and proved to be used in mixed-mode. [ABSTRACT FROM AUTHOR]

The core-shell composites were first prepared by surface modification of silica spheres with two-dimensional MOF-FDM-23 nanosheets via a simple approach. The successful immobilization of 2D MOF-FDM-23 on the silica (2D MOF-FDM-23@silica) was confirmed by series of method including elemental analysis, X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and the Brunauer–Emmett–Teller (BET). The obtained material showed excellent separation performance for multiple polar compounds such as sulfonamides, alkaloids, antibiotic and amino acid compounds etc. In addition, it was found to be superior to most reported MOF-based stationary phases in terms of separation performance, preparative reproducibility and chromatographic stability. The reproducibility of material preparation was demonstrated by the difference in retention time of the same mixture on three batches of the material at different times. The relative standard deviation (RSD) of the retention time for preparation repeatability was found to range from 0.5% to 1.4%. In short, the core-shell composite material prepared by this method broadened the application of MOF-based composites as chromatography stationary phase, and significantly developed the field of 2D MOF nanosheets in chromatography. Image 1 • A simple synthetic method for 2D MOFs nanosheets functional silica microspheres was established. • The obtained material showed excellent separation performance in HILIC mode. • The reproducibility of material was demonstrated by the difference in retention time of on the same material on time several time intervals on several days. [ABSTRACT FROM AUTHOR]

Magnetic N-doped 3D graphene-like framework carbon (Fe 3 O 4 @N-3DFC) was prepared via direct pyrolysis of sodium citrate and further hydrothermal reaction, and employed in the extraction of two cephalosporin antibiotics including cephalexin monohydrate and ceftiofur hydrochloride. The scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy and X-ray diffraction were employed to confirm the successful synthesis of 3DFC-based adsorbents (3DFCs) including 3DFC, Fe 3 O 4 @3DFC and Fe 3 O 4 @N-3DFC. Fe 3 O 4 @N-3DFC sorbent with 3D graphene-like honeycomb architecture combined magnetic and N doping shows the attractive features including graphene carbon sheets, hierarchical porous structure, good wettability and higher surface affinity for cephalosporin antibiotics. Furthermore, the comparison of extraction efficiency with raw 3DFC and Fe 3 O 4 @3DFC sorbent also confirmed the superiority of Fe 3 O 4 @N-3DFC sorbent. Under optimized conditions, good linearity lines were obtained with the determination coefficients from 0.9953 to 0.9995. The limit of detections were in the range of 0.20–0.45 μg L−1 and 0.03–0.10 μg L−1 for cephalexin and ceftiofur, respectively. The spiked extraction recoveries were between 81.59% and 98.35% with the relative standard deviation values less than 6.98%. Combined with high performance liquid chromatography, Fe 3 O 4 @N-3DFC based magnetic solid-phase extraction was successfully applied in river water and zebrafish samples analysis. 3D graphene-like framework carbon (3DFC), magnetic Fe 3 O 4 @3DFC sorbent and magnetic N-doped Fe 3 O 4 @N-3DFC composite were prepared for the extraction of cephalexin monohydrate and ceftiofur hydrochloride in river water and zebrafish samples. Image 1 • Magnetic N-doped 3D graphene-like carbon were prepared for the extraction research of two cephalosporin antibiotics. • Compared with precursor materials, Fe 3 O 4 @N-3DFC adsorbent exhibited best extraction efficiency for targets. • Selectivity experiment was constructed to evaluate the specific adsorption capacity of as-prepared adsorbent. • Fe 3 O 4 @N-3DFC based MSPE method coupled with HPLC was applied in river water and zebrafish analysis. [ABSTRACT FROM AUTHOR]