Facile fabrication of magnetic urea-based covalent organic framework for selective and efficient solid-phase extraction of parabens in soft drinks and skin toners.

Post-synthetic modification of a magnetic covalent organic framework with alkyne linkages for efficient magnetic solid-phase extraction and determination of trace basic orange II in food samples

Facile mechanochemistry synthesis of magnetic covalent organic framework composites for efficient extraction of microcystins in lake water samples

Magnetic covalent organic framework as a solid-phase extraction absorbent for sensitive determination of trace organophosphorus pesticides in fatty milk.

Facile preparation of covalent-organic framework composites for magnetic solid-phase extraction of naphthaleneacetic acid in food prior to HPLC-UV analysis

Triphenylamine (TPA)-functionalized magnetic microspheres (Fe(3)O(4)/SiO(2)/TPA) were prepared and applied as solid phase extraction (SPE) adsorbents for the analysis of polycyclic aromatic hydrocarbons (PAHs) in environmental samples in combination with high-performance liquid chromatography (HPLC). The magnetic solid-phase extraction (MSPE) conditions affecting the extraction efficiency were optimized, including elution solvent, standing time, amount of sorbent, and salt concentration. Due to the strong π-π conjugate effect between the benzene rings of TPA and PAHs, high extraction efficiency was achieved with spiked recoveries of 80.21-108.33% and relative standard deviations (RSD) of less than 10%. Good linearities (R(2) > 0.997) for all calibration curves were obtained with low limits of detection (LOD) of 0.25, 0.5, 0.5, 3.75, 0.2 and 0.04 ng L(-1) for anthracene, fluoranthene, pyrene, chrysene, benzo[b]fluoranthene and benzo[k]fluoranthene, respectively. The achieved results indicate the applicability of Fe(3)O(4)/SiO(2)/TPA as MSPE adsorbents.

Magnetic covalent organic frameworks combined with HPLC for determination of alkylphenols

Fabrication of polyethyleneimine modified magnetic microporous organic network nanosphere for efficient enrichment of non-steroidal anti-inflammatory drugs from wastewater samples prior to HPLC-UV analysis

Fabrication of magnetic covalent organic framework for effective and selective solid-phase extraction of propylparaben from food samples

A novel magnetic reduced graphene oxide nanoribbons (Fe3O4 @RGONRs) composite was prepared and applied as an adsorbent of magnetic solid-phase extraction (MSPE) for the determination of four bisphenol endocrine disrupters in three carbonated beverages coupled with high-performance liquid chromatography (HPLC). The prepared Fe3O4@RGONRs composite was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry, nitrogen adsorption-desorption isotherms and zeta potential analysis. Fe3O4@RGONRs composite possessed an abundant π-electron system and interacted with the analytes by π-π stacking, hydrophobic interactions, and hydrogen bond. The MSPE parameters, including the mass of adsorbent, sample solution pH, extraction time, ionic strength, desorption solvent and desorption time, were evaluated. Under the optimal conditions, the proposed Fe3O4@RGONRs-based MSPE method exhibited good linearity with determination coefficients (R2) between 0.9994 and 1000 from 1.6 to 1000 µg L−1, low limits of detection from 0.33 to 0.87 µg L−1, and suitable accuracy with spiked recoveries from 81.88% to 115.73%. The excellent analytical performance, along with suitable batch-to-batch reproducibility and reusability, suggest potential applications in the field of sample pretreatment.

As a promising generation of porous micro-materials, covalent organic frameworks (COFs) have great potentials for applications in separation and adsorption. In the present study, an advanced food-safety inspection method involving COFs as the adsorbents of solid phase extraction (SPE) is proposed for sensitive and accurate determination of target hazardous substances. Typical spherical TpBD COFs with large surface area and superior chemical stability were utilized as adsorbents for the preconcentration of phenolic endocrine disruptors (PEDs), followed by high performance liquid chromatography (HPLC) analysis. The well-prepared TpBD COFs were encapsulated in SPE cartridges and applied in food research, namely, for the separation and enrichment of four target endocrine disruptors in food samples. The possible factors influencing the SPE performance including the composition of the sample solvent, sample solution pH, sample flow rate, composition of the eluent, and the volume of the eluent were investigated and optimized. Due to the porous architecture and superior surface area of spherical TpBD, the enrichment of analytes via a COF-filled SPE column gave extremely low detection limits of 0.056–0.123 μg L−1 along with a wide linear range of 0.5–100 μg L−1 for all the analytes. Nine parallel determinations of the mixed standard with a concentration of 10 μg L−1 produced the relative standard deviations of 2.23–3.08%, indicating the excellent repeatability of the COF-SPE assay. This study can open up a new route for the employment of COFs as efficient SPE adsorbents for the enrichment and quantification of trace/ultra-trace hazardous materials in complex food samples.

Multivariate covalent organic frameworks guided carboxyl functionalized magnetic adsorbent for enrichment of fluoroquinolones in milk prior to high performance liquid chromatographic analysis

In this study, a simple and efficient magnetic solid-phase extraction (MSPE) strategy was developed to simultaneously purify and enrich nine mycotoxins in fruits, with the magnetic covalent organic framework nanomaterial Fe3O4@COF(TAPT-DHTA) as an adsorbent. The Fe3O4@COF(TAPT-DHTA) was prepared by a simple template precipitation polymerization method, using Fe3O4 as magnetic core, and 1,3,5-tris-(4-aminophenyl) triazine (TAPT) and 2,5-dihydroxy terephthalaldehyde (DHTA) as two building units. Fe3O4@COF(TAPT-DHTA) could effectively capture the targeted mycotoxins by virtue of its abundant hydroxyl groups and aromatic rings. Several key parameters affecting the performance of the MSPE method were studied, including the adsorption solution, adsorption time, elution solvent, volume and time, and the amount of Fe3O4@COF(TAPT-DHTA) nanomaterial. Under optimized MSPE conditions, followed by analysis with UHPLC-MS/MS, a wide linear range (0.05-200 μg kg-1), low limits of detection (0.01-0.5 μg kg-1) and satisfactory recovery (74.25-111.75%) were achieved for the nine targeted mycotoxins. The established method was further successfully validated in different kinds of fruit samples.

The quality and safety of agricultural products are strongly related to human livelihood. Thus, the government and consumers have recently paid increased attention to the quality and safety of agricultural products. The development of efficient, rapid, and sensitive analytical methods for detecting pesticides, veterinary drugs, heavy metals, mycotoxins, and environmental pollutants in agricultural products is of great significance. Owing to the complexity of many sample matrices and the low concentration of pollutants in a typical sample, appropriate sample pretreatment steps are necessary to enrich pollutants in agricultural products. Solid-phase extraction (SPE) is the most widely used sample pretreatment technology; in this technique, the adsorbent generally determines the selectivity and efficiency of the extraction process. An increasing number of novel materials have been used as SPE adsorbents. The extraction efficiency, extraction selectivity, and analytical throughput of SPE could be greatly improved by combining these novel materials with various extraction modes (e. g., solid-phase microextraction, dispersed SPE, and magnetic SPE (MSPE)) during sample preparation. Because of their large specific surface area and high affinity toward target analytes, nanomaterials are often used as SPE adsorbents, thereby greatly improving the selectivity and sensitivity of the analytical technology. More importantly, these materials have become a priority area of research on preconcentration technologies for trace compounds in agricultural products. This paper summarizes the adsorption characteristics of several new nanomaterials, including magnetic materials, carbon-based materials, metal nanomaterials (MNs), metal oxide nanomaterials (MONs), metal organic frameworks (MOFs), and covalent organic frameworks (COFs). These nanomaterials present numerous advantages, such as large specific surface areas, high adsorption capacities, and tailorable structural designs. MSPE employs magnetic materials as sorbents to afford fast dispersion and efficient recycling when applied to complex sample matrices under an external magnetic field. The use of MSPE can avoid several typical problems associated with SPE such as poor adsorbent packing and high pressure, thereby greatly simplifying the pretreatment process and providing a high flux for sample analysis. Carbon-based materials are powdered or bulk nonmetallic solid materials with carbon as the main component; carbon and nitrogen materials, mesoporous carbon, carbon nanotubes, and graphene are some examples of these materials. These materials provide large specific surface areas, abundant pore structures, good thermal stability, high mechanical strength and adsorption capacity, and controllable morphology. Pure and modified carbon nanomaterials have been successfully used to purify target analytes from agricultural products. Given their unique physical and chemical properties, MNs and MONs have attracted significant interest for use in sample preparation. MNs and MONs with excellent thermal and mechanical stabilities show good resistance to a wide pH range and diverse organic solvents, which is crucial in adsorbent-based extraction methods. The surface of these materials can be easily modified with various ligands to improve their selectivity. MOFs and COFs present many advantages such as large specific surface areas, high porosity, adjustable pore performance, and good thermal stability. Several methods that employ novel adsorbent materials to analyze pollutants in a variety of agricultural products, such as chromatography, spectroscopy, mass spectrometry, and other detection technologies, have been established. This paper also reviews the application of adsorbent materials in the analysis of agricultural product quality and safety, and discusses the future development trends of these sorbents in sample preparation for the safety analysis of agricultural products.

In this paper, based on the mechanism of the quick, easy, cheap, effective, rugged and safe (QuEChERS) method, a novel graphene grafted silica-coated Fe3O4 (Fe3O4@SiO2@G) was synthesized and applied as the efficient magnetic solid-phase extraction (MSPE) adsorbent for rapid cleanup of vegetable samples prior to analyzing 16 preservative residues by gas chromatography–mass spectrometry (GC-MS). The method, which took advantages of the novel nanoparticle adsorbent and an external magnetic field separation targets from samples, not only could avoid the time consuming of the traditional solid-phase extraction, but also could be developed for simultaneous determination of 16 preservative residues in vegetables. Various experimental parameters that could affect the extraction efficiencies have been investigated. Under the optimum conditions, 16 preservatives showed good linearity over the range of 0.02–2.00 mg/L and correlation coefficients (R 2) of 0.9946–0.9998. The limits of detections (LODs) were in the range of 0.21–11.50 μg/kg. The recoveries of 16 preservatives ranged from 78.3 to 116.7 %, and the relative standard deviations (RSDs) ranged from 1.4 to 11.9 %.

Thiol-yne click post-synthesis of phenylboronic acid-functionalized magnetic cyclodextrin microporous organic network for selective and efficient extraction of antiepileptic drugs