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In this study, a novel green adsorbent based on magnetic graphene quantum dots modified with a molecularly imprinted polymer (MGQDs@MIP) was developed for the selective detection of quercetin in complex real samples. This composite material was synthesized using an environmentally friendly approach consistent with the principles of green analytical chemistry. Quercetin, an important bioactive flavonoid, was used as a template molecule to create highly selective binding sites within the MIP structure. The resulting MGQDs@MIP exhibited excellent selectivity, sensitivity and reusability and was effectively used for the extraction and quantification of quercetin in black tea, coffee, oregano and cinnamon using a simple spectrophotometric method. The adsorbent showed a wide linear detection range (0.01–3.00 µg mL − ¹; R 2  = 0.9999, n  = 7; regression equation: y = 0.2587 − 0.0005), a low detection limit (4.88 ng mL − ¹) and high recoveries (96.97–102.97%). This work demonstrates the potential of MGQDs@MIP as a cost-effective, sustainable and efficient platform for flavonoid analysis in real samples.

This study investigated the adsorption of methyl orange (MO) from aqueous solutions using a novel MnFe₂O₄/GO nanocomposite coated with cetyltrimethylammonium bromide (CTAB). The dual-layer surfactant modification facilitates both electrostatic and lipophilic interactions. This enhancement significantly improves dye removal efficiency. The adsorption process was monitored using spectrophotometry at 464 nm, with various characterization techniques confirming the structural and magnetic properties of the nanocomposite. The optimized parameters for maximum adsorption include a 2-minute ultrasonic dispersion, pH 6.8, and a surfactant-to-adsorbent ratio of 1, achieving a maximum adsorption capacity of 285.7 mg/g. The kinetic data followed a pseudo-second-order model, whereas the adsorption isotherm aligned with the Freundlich model, indicating multilayer adsorption. Thermodynamic analysis revealed the spontaneous and exothermic nature of the process. Additionally, the magnetic properties of the nanocomposite enabled efficient separation and reusability over three cycles without significant loss of performance. This study demonstrates the potential of MnFe₂O₄/GO coated with CTAB for rapid, efficient, and reusable removal of anionic dyes from wastewater through a combined mechanism of electrostatic and hydrophobic interactions.

In this study, magnetic mesoporous silica-Fe3O4-graphene oxide nanoparticles (Fe3O4@GO@mSiO2) were synthesized and used as sorbents for magnetic solid-phase extraction (MSPE) of trace amounts of quercetin in natural samples (spinach, green pepper, dill, and red onion). The sorbent produced was characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), and X-ray photoelectron spectroscopy (XPS). The effects of various experimental factors on the percent recovery of quercetin, including extraction time, desorption time, sample solution pH, and adsorbent amount were investigated. The Fe3O4@GO@mSiO2 strategy showed excellent stability and sensitivity for the determination of quercetin, with a suitable linear range of 20–800 µg L−1 and a detection limit of 5.2 µg L−1. The data indicate that Fe3O4@GO@mSiO2 has a specific surface area and suitable adsorption capacity for the determination of quercetin.

In this study, a magnetic metal-organic framework (MOF) was synthesized based on magnetic Fe3O4, Cu(II), and benzene-1,3,5-tricarboxylic acid (Cu-BTC) as a sorbent for solid phase extraction (SPE) of trace amounts of Pb(II) in water and lettuce samples. Pb(II) ion was adsorbed on the magnetic MOF and easily separated by a magnet; therefore, no filtration or centrifugation was necessary. The analyte ions were eluted by HCl 0.5 mol·L−1 and analyzed via graphite furnace atomic absorption spectroscopy. The prepared sorbent was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and Fourier transform-infrared (FT-IR) spectroscopy. Under optimal experimental conditions, the method had a linear range of 0.1–50 μg·L−1. The limits of detection and quantitation for lead were found to be 0.026 and 0.08 μg·L−1, respectively. The results showed that the prepared sorbent has high selectivity for Pb2+ even in the presence of other interfering metal ions.

This study reports the construction of a novel SPME fiber based on chitosan and glutaraldehyde as coating material composites combined with high-performance liquid chromatography with an ultraviolet detector (HPLC-UV) for extraction and detection of phenobarbital. In this technique, the chitosan biopolymer, as a new coating of SPME fiber, was produced on the stainless-steel wire, using glutaraldehyde and phenobarbital as cross-linker and template, respectively. For comparison, a nonimprinted polymer was created using the same procedure to evaluate fiber selectivity (but without the addition of phenobarbital). The SPME-MIP fiber coating was characterized by field emission scanning electron microscopy, Fourier-transform infrared spectroscopy, and thermal gravimetric analysis. The efficiency of fiber was then improved by adjusting the impact of numerous factors such as pH, extraction time, desorption time, desorption solvent, and stirring rate. The results showed that the proposed fiber has a linear range of 0.01–4 μg·mL−1, and detection limit of 7.5 ng·mL−1. The average recoveries in the four concentration levels for the spiked river and well water samples were 95.7 and 95.3%, with relative standard deviations of 3.8 and 5.9% for single fiber and between fibers, respectively.

A graphene coating was prepared through electrochemical exfoliation of pencil graphite and then used as a fiber coating for headspace solid-phase microextraction of polycyclic aromatic hydrocarbons (PAHs) from water samples by GC analysis technique with flame ionization detector since flame ionization detector work according to the principle of ions released in the combustion of the sample species if there are any organic compounds. The graphene layers were produced by applying an anodic voltage of +2 V to the pencil graphite electrode in 1 M sulfuric acid solution as an electrolyte. The adsorbent was characterized by using scanning electron microscopy. Following thermal desorption, the PAHs (specfically naphthalene, acenaphthene, fullerene, phenanthrene, anthracene and fluoranthene) were quantified by GC. Under optimum conditions (extraction temperature, 65 °C; extraction time, 35 min; salt concentration of 20% w / v ; desorption temperature, 260 °C; desorption time, 5 min), the limits of detection range between 10 and 90 ng L −1 , and the linear ranges extend from 0.05–50 μg L −1 . The repeatability of the extraction process and the fiber-to-fiber reproducibility were in the ranges of 4.3–0.2% and 7.3–9.8%, respectively. Graphical abstract Schematic representation of electrochemical exfoliation of pencil core to prepare a headspace solid phase microextraction (HS-SPME) graphene fiber coating. After applying a voltage, the graphene nanosheets thus produced are used for determination of polycyclic aromatic hydrocarbons (PAHs) in water samples.

In this project, a nanosorbent was prepared using graphene oxide nanosheets modified with a specific mercury aptamer to detect very low mercury concentrations in aqueous solutions. The properties of the prepared nanosheets as adsorbents in the adsorption of mercury cations by microextraction in a packed syringe and analysis with a spectrophotometer were evaluated. Scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray energy diffraction were used to characterize the nanosheets obtained. The optimization conditions affecting the extraction and determination of mercury by spectrophotometry such as the influence of the pH of the aqueous solution, the number of sample loading times, the number of desorption times, the contact time of the analyte with the adsorbent, the amount of adsorbent and the volume of wash solvent were investigated. Under optimization conditions, the calibration curve of the method was linear between 20 and 800 μg L −1 , and the detection limit of the method was 2.2 μg L −1 . Mercury analysis in real samples such as Gavoshan dam water, Gamasiab river water and Bashir Taq Bostan spring water was also investigated to evaluate the method.

A zirconium-based MOF (UiO-66-NH 2 ) with thiol groups attached to its magnetic corn surface was used for the adsorption and extraction of Au(III) from electronic waste. The composite was characterized using FTIR, XRD, FESEM, TGA, and BET techniques. The effects of the temperature, adsorption period, and pH on Au(III) adsorption were investigated. The optimal conditions to achieve the maximum adsorption of Au(III) on the adsorbent surface were pH 6.0, 50◦C, 40 min, and 10 mg of adsorbent. Moreover, oxidized magnetic corncobs functionalized with thiol (OCBs@Fe 3 O 4 @UiO-66-SH) showed a notable ability to adsorb Au(III), with a capacity of 1587 mg/g. With the mass ratios of Au(III) to competing ions (Mg, Mn, Cu, Zn, Co, Cd, and Ni) fixed at 1:1 or extended to 1:5, this adsorbent prefers Au(III) ions while showing negligible adsorption to other ions. This study validated a technique to extract Au (III) from various electronic waste samples, achieving high recoveries  (95.30% to 104.75%), demonstrating its effectiveness and lack of matrix interference. Examining various isotherm and kinetic models demonstrated that the Langmuir and pseudo-first-order models could effectively interpret the experimental and kinetic data. Thermodynamic calculations showed that the adsorption process is endothermic and occurs spontaneously. The optimal utilization of renewable waste as an adsorbent base, high adsorption capacity, recoverability, and reusability owing to its magnetic properties, high recovery rate of Au(III) from electronic matrices, and highly selective adsorption in the presence of competing ions are among the advantages of this adsorbent. Together, these features highlight the novelty of the present study. Graphical Abstract

A zirconium-based MOF (UiO-66-NH.sub.2) with thiol groups attached to its magnetic corn surface was used for the adsorption and extraction of Au(III) from electronic waste. The composite was characterized using FTIR, XRD, FESEM, TGA, and BET techniques. The effects of the temperature, adsorption period, and pH on Au(III) adsorption were investigated. The optimal conditions to achieve the maximum adsorption of Au(III) on the adsorbent surface were pH 6.0, 50â¦C, 40 min, and 10 mg of adsorbent. Moreover, oxidized magnetic corncobs functionalized with thiol (OCBs@Fe.sub.3O.sub.4@UiO-66-SH) showed a notable ability to adsorb Au(III), with a capacity of 1587 mg/g. With the mass ratios of Au(III) to competing ions (Mg, Mn, Cu, Zn, Co, Cd, and Ni) fixed at 1:1 or extended to 1:5, this adsorbent prefers Au(III) ions while showing negligible adsorption to other ions. This study validated a technique to extract Au (III) from various electronic waste samples, achieving high recoveries (95.30% to 104.75%), demonstrating its effectiveness and lack of matrix interference. Examining various isotherm and kinetic models demonstrated that the Langmuir and pseudo-first-order models could effectively interpret the experimental and kinetic data. Thermodynamic calculations showed that the adsorption process is endothermic and occurs spontaneously. The optimal utilization of renewable waste as an adsorbent base, high adsorption capacity, recoverability, and reusability owing to its magnetic properties, high recovery rate of Au(III) from electronic matrices, and highly selective adsorption in the presence of competing ions are among the advantages of this adsorbent. Together, these features highlight the novelty of the present study. Graphical

In this paper, a straightforward method is presented to detect valproic acid after its microextraction. Molecularly imprinted polymer fiber was used in conjunction with chromatography-flame ionization to achieve this goal. A narrow bore silica capillary was adopted as a mold, via the copolymerization of meth acrylic acid–ethylene glycol dimethacrylate imprinted with VPA, to synthesize the fiber. Extraction temperature, extraction time, salt addition, pH, stirring rate, and desorption temperature—all of which are factors that can influence the extraction process—were measured, and adjusted accordingly. Linearity, precision, and detection limits, as analytical elements, were also evaluated under optimum conditions. Readings showed a linear range of 0.03–100 µg L− 1 (r2 = 0.998), and the limit of detection was measured as 0.01 µg L− 1. The established method was then applied in selective detection of valproic acid in tablet, syrup and human serum samples successfully.