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A general method was developed for preparing a metal–organic framework–polymer composite coated silica core–shell stationary phase. Silica microspheres were comodified with metal–organic framework and polyvinylpyrrolidone rather than the in situ method of silica modification by original metal–organic framework particles. Metal–organic framework particles and polyvinylpyrrolidone on silica surface were beneficial to suppress silanol activity and enhance composite material tolerance, as well as increasing the water compatibility of the original metal–organic framework-based stationary phases. The stationary phase exhibited superior hydrophilic and hydrophobic performance in terms of separation for various analytes including seven alkaloids, six sulfonamides, five antibiotics, and five polycyclic aromatic hydrocarbons. Moreover, the composite material also showed excellent stability with the relative standard deviation of the retention time of 0.4 to 0.7%. The separation performance with real samples proved that the column has good practical application potential. In summary, the poposed method provides a general way for preparing metal–organic framework–polymer composite material and changed the current status of original metal–organic framework particles modified silica as a single mode chromatographic stationary phase. [ABSTRACT FROM AUTHOR]

The authors describe a filter paper modified with mesoporous silica that carries phenylboronic acid on its surface. The material possesses the advantages of the flexibility of filter paper and the large surface of mesoporous silica. This makes it an excellent sorbent for the enrichment of trace quantities of nucleosides. The limits of detection (in HPLC analysis with UV detection) are 2.0-11.1 μg L and the limits of quantification are 6.8-37.1 μg L with good precision (RSD < 6.4%). Compared to plain filter paper and nonporous silica-coated filter paper, the material exhibits enhanced efficiency and a 4.5-fold improved capacity. The potential applications are demonstrated by preconcentrating nucleosides from HepG2 cells which are a representative complex sample. The method was also used to study the effect of 30-nm gold nanoparticle on cellular metabolism. [ABSTRACT FROM AUTHOR]

A new stationary phase containing primary amine and tertiary amine groups was synthesized and its structure was confirmed by infrared spectra, elemental analysis, and zeta potential. This new material was packed into a stainless steel column and the effect of acetonitrile (ACN) content in mobile phase on retention was evaluated using probes of nucleosides, sulfanilamides, and quinolone compounds. This showed hydrophilic interaction, ion interaction, or a mixed-mode retention mechanism for different kinds of solutes, respectively. The effects of the pH and ion strength of the mobile phase were investigated to further understand the retention mechanism of the new stationary phase. The interaction forces caused by the new phase included adsorption, electrostatic function, and ion exchange. The new material could be used as a stationary phase in different high-performance liquid chromatography modes. [ABSTRACT FROM AUTHOR]

Solid-phase microextraction coupled to high-performance liquid chromatography (SPME-HPLC) with fluorescence detection was employed to determine bisphenol A (BPA) in milk samples. The potential influence of the milk matrix on the determination of BPA by SPME-HPLC were investigated. Optimal conditions to eliminate any matrix effects were as follows: milk samples were deproteinized with trichloroacetic acid, diluted 20-fold with BPA-free Ultrapure water, dissolved in methanol, the precipitated protein was filtered out, rinsed with methanol and evaporated to remove the methanol. Then, a 40.0-ml solution was used for SPME extraction and HPLC analysis. Satisfactory recoveries (milk: 93.1-101%; soybean milk: 93.9-102%) were achieved. The proposed method was successfully applied to real samples, BPA being detected within the range 1.6-2.6 ng ml-1 in four brands of commercial milk but not in soybean milk. [ABSTRACT FROM AUTHOR]

A high performance liquid chromatographic method (HPLC) with precolumn derivatization and fluorescence detection for insulin was developed and applied for the quantification of insulin in spiked serum. To covalence couple with insulin, 4‐chloro‐7‐nitrobenzo‐2‐oxa‐1,3‐diazole (NBD‐Cl) was selected as fluorescent reagent. The optimal derivatization conditions were as follows: temperature 50; time 2 h, in the dark; 0.1 M phosphate buffer (pH 9.0). Analytical separation was carried out on a C18 column and the mobile phase including acetonitrile‐water containing 0.1% trifluoroacetic acid (TFA) (v/v&ratio; 30/70). The excitation/emission wavelengths were 470/540 nm. Under the conditions, the retention time and capacity factor of the adduct of insulin‐NBD were 10.03 min (flow rate 1 mL/min) and 3, respectively. The recovery of insulin in serum was 95.06% and the detection limit was 90 nM. In the investigated concentration ranges (0.46 µM&nvsim;16.10 µM), R 2 was 0.9934, which indicated the potential for the application of NBD‐Cl derivatization to the analysis of insulin in the biological matrices, although with the shortcoming of long analytical time. [ABSTRACT FROM AUTHOR]

Vicine in leaves, seeds and fruits of bitter melon were determined with HPLC for the first time. Vicine was extracted with water by ultrasonic, and separated with other substances with C18 reverse phase column. The mobile phase was methanol/0.025 mol/L phosphate buffer (pH 3.0)(10/90, v/v). The effects of the content of methanol and pH on the analysis of vicine were discussed. The recovery of vicine in each sample was between 93% and 105%. The content of vicine in seeds, leaves, and fruits of bitter melon were 0.524%, 0.0456%, 0.115%, respectively. [ABSTRACT FROM AUTHOR]

A hybrid material was prepared from graphene oxide and melamine sponge, and modified with phenylboronic acid to obtain a sorbent for the enrichment of the nucleosides cytidine, uridine, inosine, guanosine and adenosine. The loading capacity typically is around 27.8 mg g−1 which is comparable to other sorbents, and highly selectivity for cis-diols is observed even if the concentration of potential interferents is 1500-fold higher. The sorbent was placed in an injector, and the process was operated semiautomatically by using a peristaltic pump. The sorbent is stable and can be re-used six times without decrease in efficiency. It was applied to the selective extraction of the cis-diols (cytidine, uridine, inosine, guanosine, adenosine) from HepG2 cells. It presents good linear between 3 to 5000 μg L−1 and the limits of detection (in HPLC analysis with UV detection) are 1-4 μg L−1. Good recoveries of 85-101% were obtained with spiked HepG2 cells samples, with relative standard deviation of ≤9.9%.Schematic for the preparation of boronic acid modified graphene oxide/melamine sponge composite for in-syringe solid-phase extraction of nucleosides. [ABSTRACT FROM AUTHOR]

A facile method for efficient synthesis of core-shell composite material was proposed. In this method, the silica microspheres were co-modified with metal organic framework (MOF-235) and polyethylene glycol polymer (PEG) and used as mixed-mode stationary phase (MOF-235@PEG@silica) for high-performance liquid chromatography. Elemental analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and Brunauer-Emmett-Teller etc. methods were used to investigate the properties of the core-shell composite material. The MOF-235@PEG@silica stationary phase showed flexible selectivity for the separation of both hydrophilic and hydrophobic compounds especially for the separation of nine alkaloids, which showed superior hydrophilic separation performance than previous MOF-based composite stationary phases. Some factors including the pH of buffer salt, the ratio of organic phase and water phase in the mobile phase have been investigated, suggesting that the chromatographic retention mechanism of the column was a mixed mode of hydrophilic and reversed phase. The composite material also showed excellent chromatographic repeatability with the RSDs of the retention time found to be 0.2%–0.6% (n = 10) and the standard addition test in the actual sample proved that it can be used for practical sample analysis. In short, it provided a general way for preparing MOFs-based composites as mixed-mode chromatographic stationary phases, and changed the current status of MOF-based composite materials as single mode chromatographic stationary phases. Image 1 • A facile method for efficient synthesis of core-shell composite material was proposed. • The stationary phase showed flexible selectivity for separation of both hydrophilic and hydrophobic compounds. • The composite materials exhibited excellent chromatographic repeatability and stability. [ABSTRACT FROM AUTHOR]

A clear formation mechanism is essential for the controllable synthesis of nanomaterials with different optical properties, which is also one of the challenges facing the preparation of fluorescent silicon nanomaterials. In this work, a one-step room temperature synthesis method was established to prepare yellow-green fluorescent silicon nanoparticles (SiNPs). The obtained SiNPs exhibited excellent pH stability, salt tolerance, anti-photobleaching ability and biocompatibility. Based on X-ray photoelectron spectroscopy, transmission electron microscopy, ultra high performance liquid chromatography tandem mass spectrometry and other characterization data, the formation mechanism of the SiNPs was proposed, which provided a theoretical basis and important reference for the controllable preparation of SiNPs and other fluorescent nanomaterials. In addition, the obtained SiNPs illustrated excellent sensitivity for nitrophenol isomers, the linear range of o-nitrophenol, m-nitrophenol, p-nitrophenol was 0.05–600 μM, 20–600 μM and 0.01–600 μM under the λ ex and λ em were set as 440 nm and 549 nm, and related limit detection was 16.7 nM, 6.7 μM and 3.3 nM, respectively. The developed SiNP-based sensor achieved satisfactory recoveries in detecting nitrophenol isomers in a river water sample, showing great promise in practical applications. Fluorescent SiNPs with excellent performance were prepared at room temperature reaction. The formation mechanism of the SiNPs was proposed and the obtained SiNPs exhibited excellent performance to nitrophenol isomers detection. [Display omitted] [ABSTRACT FROM AUTHOR]

The exploration of advanced porous materials in separation science has received great attention for analytical chemistry, and chromatographic separation is also an important process in analytical chemistry. Metal−organic frameworks (MOFs) have emerged as a special class of porous crystalline materials, the unique features like framework flexibility and chirality make MOFs very attractive than other classes of porous materials. With the development of water-stability MOFs and post-modification technology, the increasingly active exploration of MOFs and MOF-based composites has been witnessed for widespread liquid phase applications. This review briefly summarizes the performances and recent application or progress of MOF-based core-shell composites used as stationary phases in the field of high-performance liquid chromatography. It provides a detailed discussion about the application of MOF-based composites for separating analytes under different conditions. Finally, the challenges and prospects about the application of core-shell MOF-based composites in separation science by means of core-shell MOF-based composites are described. • Different types of core-shell MOFs-based composites are introduced. • Applications of MOFs-based composites in chromatographic separation under different conditions are summarized in details. • The challenges and prospects for MOFs-based composites in chromatographic science are described. [ABSTRACT FROM AUTHOR]

• The pore size of the core–shell silica particles was enlarged by phenylethanol. • Well-defined fibrous shell was coated on the core with tunable pore size from 4 nm to 19 nm. • End-capped group imidazole improved the separation resolutions on the C8 column. The core–shell particles with tunable pore size were synthesized by a bi-phase reaction successfully. By adjusting the amount of phenylethanol, fibrous shells with tunable pore sizes ranging from 4 to 19 nm could be obtained in one pot. The obtained silica microspheres were used for chromatographic separation after modification with octyltrichlorosilane and end-capping with N-(trimethoxysilylpropyl)imidazole. Better resolutions of nitroimidazoles and anilines were obtained on the end-capped stationary phase. This particle could serve as an HPLC stationary phase with good reproducibility and particular selectivity. [ABSTRACT FROM AUTHOR]

Abstract: Octyl (C8) or octadecyl (C18)-modified mesoporous SBA-15 silica molecular sieves have been prepared by adding SBA-15 silica molecular sieves to octyltrimethoxysilane or octadecyltrimethoxysilane in toluene at 100°C, and characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), nitrogen adsorption–desorption measurements, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). FTIR spectra shows the presence of methylene (–CH2–) and methyl (–CH3) bands on the modified SBA-15. Powder XRD data indicate the structure of modified SBA-15 with octyl or octadecyl groups still remains two-dimensional hexagonal mesostructrure. Brunauer–Emmett–Teller (BET) surface area analysis presents that surface area of octyl- and octadeyl-SBA-15 changed from 647 to 449 and 321m2 g−1, respectively, and SEM images show the decreased size of modified SBA-15 particles. TEM images of modified materials with alkyl groups show the structures remain the same as the parent SBA-15 silica. We also have studied the adsorption capacity of the materials to phthalate esters (dimethyl and diethyl phthalate) by dynamic adsorption experiments on high performance liquid chromatography (HPLC). It is found that the modified materials can increase the adsorption of phthalate esters compared to SBA-15 particles, and the adsorption capacity increased with the increased length of alkyl chain on SBA-15. The maximum dynamic adsorption capacity for diethyl phthalate was 3.9 (C8-SBA-15) or 4.3 (C18-SBA-15) times higher than that of SBA-15 particles, respectively. The results indicate that alkyl SBA-15 particles could be used for enrichment of phthalate esters in water samples before the further analysis. [Copyright &y& Elsevier]

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]

A kind of new temperature sensitive molecularly imprinted polymer (MIP) with ofloxacin (OFL) as template was prepared for the coating of solid phase microextraction (SPME). Dopamine was self-polymerized on stainless steel fiber (SSF) as the SPME support followed by silanization. Then MIP was synthesized as SPME coating on the modified SSF in a capillary, with N -isopropyl acrylamide as temperature sensitive monomer and methacrylic acid as functional monomer. The synthesis could be well repeated with multiple capillaries putting in the same reaction solution. The obtained MIP fiber was evaluated in detail with different techniques and various adsorption experiments. At last the MIP fiber was used to extract the OFL in milk. Satisfied recoveries between 89.7 and 103.4% were obtained with the limit of quantification (LOQ LC ) of 0.04 μg mL −1 by the method of SPME coupled with high performance of liquid chromatography (HPLC). [ABSTRACT FROM AUTHOR]

Highlights: [•] We used click reaction to prepare a new type of polymer as the monolith column. [•] The polymer was porous and could enrich PAHs well up to 100 to more than 1000 times. [•] The π–π stacking interaction and the effect of small size played dominant roles to the strong adsorption affinity of the polymer monolith. [•] A sensitive on-line SPME–HPLC method was set up for determination of PAHs. [Copyright &y& Elsevier]

Abstract: Focused metabolic profiling is a powerful tool for the determination of biomarkers. Here, a more global proton nuclear magnetic resonance (1H NMR)-based metabolomic approach coupled with a relative simple ultra high performance liquid chromatography (UHPLC)-based focused metabolomic approach was developed and compared to characterize the systemic metabolic disturbances underlying esophageal cancer (EC) and identify possible early biomarkers for clinical prognosis. Serum metabolic profiling of patients with EC (n=25) and healthy controls (n=25) was performed by using both 1H NMR and UHPLC, and metabolite identification was achieved by multivariate statistical analysis. Using orthogonal projection to least squares discriminant analysis (OPLS-DA), we could distinguish EC patients from healthy controls. The predictive power of the model derived from the UHPLC-based focused metabolomics performed better in both sensitivity and specificity than the results from the NMR-based metabolomics, suggesting that the focused metabolomic technique may be of advantage in the future for the determination of biomarkers. Moreover, focused metabolic profiling is highly simple, accurate and specific, and should prove equally valuable in metabolomic research applications. A total of nineteen significantly altered metabolites were identified as the potential disease associated biomarkers. Significant changes in lipid metabolism, amino acid metabolism, glycolysis, ketogenesis, tricarboxylic acid (TCA) cycle and energy metabolism were observed in EC patients compared with the healthy controls. These results demonstrated that metabolic profiling of serum could be useful as a screening tool for early EC diagnosis and prognosis, and might enhance our understanding of the mechanisms involved in the tumor progression. [Copyright &y& Elsevier]

Abstract: A molecularly imprinted polymer was synthesized by ultrasonic irradiation, with attapulgite as matrix using β-naphthol as the template molecule, acryloyl-β-cyclodextrin as the functional monomer, and N,N-methylenebiacrylamide as the cross-linking agent, respectively. The imprinted polymer was characterized by infrared spectroscopy and transmission electron microscopy. Compared to polymers prepared by traditional heat sources, the molecularly imprinted polymer synthesized by ultrasonic irradiation had better selectivity and faster adsorption kinetics to estriol, estradiol, estrone and diethylstilbestrol. Using the imprinted polymer as the packing material for on-line solid-phase extraction, the above four estrogens in milk samples were concentrated and analyzed. The limits of detection for these estrogens were in the range of 1–8ngg−1 and reproducibility were less than 5.1% as RSDs (n =6) with milk samples spiked at 100 and 1000ngg−1 of each analyte. [Copyright &y& Elsevier]

Abstract: A porous polysulfone microcapsule containing organic modified montmorillonite and magnetic nanoparticles (OMMT-Fe3O4@PSF) has been successfully prepared by a phase-inversion method and evaluated as a magnetic solid-phase extraction (MSPE) sorbent for clean-up and enrichment of 4-chlorophenol (4-CP) and 2-chlorophenol (2-CP) in aqueous samples. Compared with a microcapsule containing the conventional extraction sorbent C18 (C18-Fe3O4@PSF), OMMT-Fe3O4@PSF had much lower cost, a faster adsorption rate, and superior uptake amounts for the investigated analytes. The proposed microcapsule has been developed for the extraction of 4-CP and 2-CP from environmental water samples and their analysis by high-performance liquid chromatography with UV detection (HPLC-UV). Various parameters, such as pH, extraction time, the mass of sorbent, and the desorption conditions, have been evaluated and the calibration curves of the chlorophenols were linear (R 2 ≥0.9985) in the range from 1.01 to 104.5ngmL−1. The limits of detection at a signal-to-noise (S/N) ratio of 3 were 0.22 and 0.17ngmL−1 and the limits of quantification calculated at S/N=10 were 1.52 and 1.07ngmL−1 for 2-CP and 4-CP, respectively. The recoveries of 2-CP and 4-CP from natural water and the treated wastewater samples were in the range of 84.4–115% with relative standard deviations (RSDs) lower than 7.0%. The results have demonstrated the suitability of the MSPE approach for the analysis of trace chlorophenols in aqueous samples. [Copyright &y& Elsevier]

Abstract: An imidazoline was prepared by solvent-free microwave-assisted organic synthesis and immobilized on porous silica particles by polymerization. The resulting material was composed of both hydrophobic alkyl ester chains and hydrophilic imidazoline rings, which gave it both hydrophilic interaction and reversed-phase characteristics. The titration curve suggests that the new material has buffering capacity and acquires increasing positive charge over the pH range 9–4, and is “zwitterionic” in the upper part of this pH range. Through investigating the effect of column temperature, the water content, pH and ion strength of mobile phase on the retention time of polar compounds in highly organic eluents, it was found that the new material could be used as a hydrophilic interaction liquid chromatography (HILIC) stationary phase which involved a complex retention process consisting of partitioning, surface adsorption and electrostatic interactions. In addition, the retention behavior of aromatic compounds in different mobile phase conditions was also studied, which showed the new material mainly exhibited a partitioning mechanism in the reversed-phase liquid chromatography (RPLC) mode. The separation of six water-soluble vitamins and five aromatic compounds were achieved by using the new material in the HILIC and RPLC modes, respectively. [Copyright &y& Elsevier]

Abstract: A simple imprinted amino-functionalized silica gel material was synthesized by combining a surface molecular imprinting technique with a sol–gel process for solid-phase extraction–high performance liquid chromatography (SPE–HPLC) determination of diethylstilbestrol (DES). Activated silica gel was used as the supporter and non-imprinted silica sorbent was synthesized without the addition of DES using the same procedure as that of DES-imprinted silica sorbent. Compared with non-imprinted polymer particles, the prepared DES-imprinted silica sorbent showed high adsorption capacity, significant selectivity, good site accessibility and fast binding kinetics for DES. The maximum static adsorption capacity of the DES-imprinted and non-imprinted silica sorbent for DES was 62.58mgg−1 and 19.89mgg−1, respectively. The relatively selective factor value of this DES-imprinted silica sorbent was 61.7 at the level of 50mgL−1. And the uptake kinetics was fairly rapid so that the adsorbent equilibrium was achieved within 10min. Furthermore, the DES-imprinted polymers were used as the sorbent in solid-phase extraction to determine DES in fish samples. The MIP–SPE–HPLC method showed higher selectivity and good recoveries higher than 87.5% (R.S.D. 11.6%). [Copyright &y& Elsevier]

Abstract: A simple and environmentally friendly method for determination of seven phenols using solid-phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC) has been developed. Several materials were used as stationary phase of SPME fibers and an oxidized multiwalled carbon nanotubes material was found to be effective in carrying out simultaneous extraction of phenols in aqueous samples. Compared with the widely used commercially available SPME fibers, this proposed fiber had much lower cost, longer lifetime (over 150 times), shorter analysis time (30min of extraction and 3min of desorption time) and comparable or superior extraction efficiency for the investigated analytes. The extraction and desorption conditions were evaluated and the calibration curves of seven phenols were linear (R 2 ≥0.9908) in the range from 10.2 to 1585ngmL−1. The limits of detection at a signal-to-noise (S/N) ratio of 3 were 0.25–3.67ngmL−1, and the limits of quantification calculated at S/N=10 were 0.83–12.25ngmL−1 for these compounds. The possibility of applying the proposed method to environmental water samples analysis was validated. [Copyright &y& Elsevier]

Abstract: A novel and simple imprinted amino-functionalized silica gel material was synthesized by combining a surface molecular imprinting technique with a sol–gel process on the supporter of activated silica gel for solid-phase extraction-high performance liquid chromatography (SPE-HPLC) determination of bisphenol A (BPA). Non-imprinted silica sorbent was synthesized without the addition of BPA using the same procedure as that of BPA-imprinted silica sorbent. The BPA-imprinted silica sorbent and non-imprinted silica sorbent were characterized by FT-IR and the static adsorption experiments. The prepared BPA-imprinted silica sorbent showed high adsorption capacity, significant selectivity and good site accessibility for BPA. The maximum static adsorption capacity of the BPA-imprinted and non-imprinted silica sorbent for BPA was 68.9 and 34.0mgg−1, respectively. The relatively selective factor value of this BPA-imprinted silica sorbent was 4.5. Furthermore, the difference of the retention characteristics of BPA on the C8 SPE column and BPA-imprinted silica SPE (MIP-SPE) was compared. The MIP-SPE-HPLC method showed higher selectivity to BPA than the traditional SPE-HPLC method. At last, the BPA-imprinted polymers were used as the sorbent in solid-phase extraction to determine BPA in water samples with satisfactory recovery higher than 99% (R.S.D. 3.7%). [Copyright &y& Elsevier]