Extraction of phenolic compounds from water samples by dispersive micro-solid-phase extraction

Monitoring of priority pollutants chlorophenols in water and milk by headspace solid-phase microextraction based on electrospun polycaprolactam nanofibers decorated with cadmium oxide-carbon nanotubes

Priority pollutants chlorophenols are broadly used chemicals that are persistent in the environment and causing serious human health hazards. The current study introduces a novel adsorbent for the extraction of chlorophenols from river water, surface water, and milk by headspace solid-phase microextraction coupled with gas chromatography. The adsorbent composite was prepared by blending polycaprolactam (nylon-6) mat and newly synthesized carbon nanotubes decorated with cadmium oxide nanoparticles followed by electrospinning technique to produce based nanofiber. The proposed nanofiber was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction techniques. The main parameters that affect extraction efficiency, including ionic strength, extraction time, desorption time, and extraction temperature, were investigated and optimized. The linear range was 0.05-5 ng/mL; the limits of detection (signal/noise=3) were 0.02-0.04 ng/mL. The relative recoveries for real samples (river water, surface water, and milk) were in the range of 84-114%.

Simple magnetization of Fe3 O4 /MIL-53(Al)-NH2 for a rapid vortex-assisted dispersive magnetic solid-phase extraction of phenol residues in water samples

The present work describes a simple route to magnetize MIL-53(Al)-NH₂ sorbent for rapid extraction of phenol residues from environmental samples. To extend the applications and performances of the metal-organic frameworks in the field of adsorption materials, we combined the properties of metal-organic frameworks and magnetite to decrease the extraction time and simplify the extraction process as well. In this study, a simple and quick vortex-assisted dispersive magnetic solid phase extraction method for the extraction of ten United States Environmental Protection Agency's priority phenols from water samples prior to analysis by high-performance liquid chromatography with photodiode array detection was proposed. The developed method exhibits a rapid enrichment of the target analytes within 10 s for extraction and 10 s for desorption. Low detection limits of 1.8-41.7 µg/L and quantitation limits of 6.0-139.0 µg/L with the relative standard deviations for intra- and interday analyses less than 12% were achieved. Satisfactory recoveries in the range of 80-111% with the relative standard deviations less than 11% demonstrated that Fe₃ O₄ /MIL-53(Al)-NH₂ is promising sorbent in the field of magnetic solid-phase extraction for environmental samples.

Layered porous organic frameworks as a novel adsorbent for the solid phase extraction of chlorophenols prior to their determination by HPLC-DAD

A layered porous organic framework (L-POF) with high surface area and porous volume was used as a novel adsorbent for adsorption of chlorophenols (CPs). The L-POF showed much higher adsorption capacity for four CPs (2-CP, 3-CP, 2,3-CP, 2,4-CP) compared with corresponding amorphous POF and some commercial adsorbents. Then, an L-POF-based solid-phase extraction method combined with high-performance liquid chromatography for analyzing CPs at the wavelength of 280 nm in water and honey samples was established. Under the optimum conditions, four CPs exhibited good linearity in the range 0.10-80.0 ng mL^-1 for water and 2-400 ng g^-1 for honey samples with determination coefficient r² > 0.996. The method has low limits of detection of 0.03-0.10 ng mL^-1 for water and 0.5-1.0 ng g^-1 for honey samples. The method presented satisfactory precision and accuracy with relative standard deviations ≤ 7.8% and recoveries of 80-115%. High enrichment factors of 123-190 for water and 63-97 for honey were obtained. The validated method was successfully used to determine CPs in water and honey samples. The L-POF also displayed prominent adsorption performance for many other dyes and organic contaminants. This suggests that it can be an ideal candidate as adsorbent for wide application in separation and analysis. Graphical Abstract.

A nanosized magnetic metal-organic framework of type MIL-53(Fe) as an efficient sorbent for coextraction of phenols and anilines prior to their quantitation by HPLC

The authors describe the synthesis of a magnetic metal-organic framework (MOF) of type MIL-53(Fe) for coextraction of phenols and anilines from various environmental samples. A quick method for dispersive micro-solid phase extraction (D-μ-SPE) was developed for coextraction of the analytes 4-nitrophenol (4-NP), 4-chlorophenol (4-CP), 4-chloroaniline (4-CA), 1-amino-2-naphtol (1-A2N) and 2, 4-dichloroaniline (2, 4-DCA). The MOF was characterized by SEM, TEM, FT-IR, EDS, thermogravimetry, VSM and XRD. The method was optimized by response surface methodology combined with desirability function approach, specifically with respect to pH value of the sample, amount of sorbent, sorption time, salt concentration, sample volume, type and volume of the eluent, and elution time. Following elution with acetonitrile, the analytes were quantified by HPLC with photodiode array detection. Responses are linear in 0.1-2000 μg·L^-1 concentration ranges. The limits of detection and relative standard deviations (for n = 5) are in the range of 0.03-0.2 μg·L^-1 and 3.5-12.6%, respectively. Enrichment factors are 113, 61, 87, 144 and 114 for 4-NP, 4-CP, 4-CA, 1-A2N and 2,4-DCA, respectively. Recoveries from spiked samples ranged from 39.5 to 93.3%. The magnetic sorbent was successfully applied to the coextraction and determination of the analytes in river, rain and hookah water samples. Graphical abstract Schematic presentation for the synthesis of (a) Fe₃O₄ nanoparticles (NPs) and (b) Fe₃O₄@MIL-53(Fe). Fe₃O₄@MIL-53(Fe) was employed as a new nanosorbent in dispersive micro-solid phase extraction of phenols and anilines. The limits of detection are in the range of 0.03-0.2 μg·L^-1.

Ligand fishing of anti-neurodegenerative components from Lonicera japonica using magnetic nanoparticles immobilised with monoamine oxidase B

In this work, monoamine oxidase B was immobilised onto magnetic nanoparticles to prepare a new type of affinity solid-phase extraction adsorbent, which was used to extract the possible anti-neurodegenerative components from the Lonicera japonica flower extracts. Coupled with high-performance liquid chromatography with mass spectrometry, two monoamine oxidase B ligands were fished-out and identified as isochlorogenic acid A and isochlorogenic acid C, which were found to be inhibitors of the enzyme for the first time, with similar half maximal inhibitory concentration values of 29.05 ± 0.49 and 29.77 ± 1.03 μM, respectively. Furthermore, equilibrium-dialysis dissociation assay of enzyme-inhibitor complex showed that both compounds have reversible binding patterns to monoamine oxidase B, and kinetic analysis demonstrated that they were mixed-type inhibitors for monoamine oxidase B, with K_i and K_is values of 9.55 and 37.24 μM for isochlorogenic acid A, 9.53 and 35.50 μM for isochlorogenic acid C, respectively. The results indicated that isochlorogenic acid A and isochlorogenic acid C were the major active components responsible for the anti-degenerative activity of the flowers of L. japonica, while magnetic nanoparticles immobilised monoamine oxidase B could serve as an efficient solid-phase extraction adsorbent to specifically extract monoamine oxidase B inhibitors from complex herbal extracts.

Fabrication of a magnetic metal–organic framework molecularly imprinted polymer for extraction of anti-malaria agent hydroxychloroquine

A new magnetic metal–organic framework molecularly imprinted polymer was synthesized by the sol–gel method for the determination of hydroxychloroquine sulfate.

Innovative method for the enrichment of high-polarity bioactive molecules present at low concentrations in complex matrices

Ginsenoside Rg1 is a valuable bioactive molecule but its high polarity and low concentration in complex mixtures makes it a challenge to separate Ginsenoside Rg1 from other saponins with similar structures, resulting in low extraction efficiency. The successful development of effective Rg1 molecularly imprinted polymers that exhibit high selectivity and adsorption may offer an improved method for the enrichment of active compounds. In this work, molecularly imprinted polymers were prepared with two different methods, precipitation polymerization or surface imprinted polymerization. Comparison of the adsorption abilities showed higher adsorption of the surface molecularly imprinted polymers prepared by surface imprinted polymerization, 46.80 mg/g, compared to the 27.74 mg/g observed for the molecularly imprinted polymers prepared by precipitation polymerization. Therefore, for higher adsorption of the highly polar Rg1, surface imprinted polymerization is a superior technique to make Rg1 molecularly imprinted polymers. The prepared surface molecularly imprinted polymers were tested as a solid-phase extraction column to directionally enrich Rg1 and its analogues from ginseng tea and total ginseng extracts. The column with surface molecularly imprinted polymers showed higher enrichment efficiency and better selectivity than a C₁₈ solid-phase extraction column. Overall, a new, innovative method was developed to efficiently enrich high-polarity bioactive molecules present at low concentrations in complex matrices.