Preparation of magnetized polycaprolactone composite and its use in stirring–dependent magnetic dispersive solid phase extraction combined with dispersive liquid–liquid microextraction

Highly efficient and simultaneous magnetic solid phase extraction of heavy metal ions from water samples with l-Cysteine modified magnetic polyamidoamine dendrimers prior to high performance liquid chromatography

Due to the strong metal-sulfur interaction between mercapto groups and metal ions, which can be used to functionalize polyamidoamine dendrimer decorated Fe₃O₄ nanoparticles for high enrichment of trace heavy metal ions from waters. Based on this concept, polyamidoamine dendrimer modified Fe₃O₄ nanomaterials were functionalized with l-Cysteine and a new magnetic solid phase extraction for rapid adsorption and separation of Hg²⁺, Pb²⁺, Co²⁺ and Cd²⁺ from waters was established. The factors affecting extraction efficiency have been optimized. Upon the optimal parameters, the established method provided good linear ranges of 0.1-200 μg L^-1 for Hg²⁺ and 0.05-200 μg L^-1 for Pb²⁺, Co²⁺ and Cd²⁺, and high sensitivity with limits of detection (LOD) of 0.018 μg L^-1, 0.014 μg L^-1, 0.013 μg L^-1 and 0.025 μg L^-1 for Cd²⁺, Pb²⁺, Co²⁺ and Hg²⁺, respectively. Real water samples were utilized to validate the proposed method, and achieved results revealed that the proposed method was sensitive, effective, stable and suitable for monitoring Pb²⁺, Cd²⁺, Co²⁺and Hg²⁺ in environmental waters. This work provided a novel strategy for the simultaneous analysis of target cations in waters, and a new direction for developing decoration method of nanomaterials according to specific purpose.

Bioinspired polydopamine-mediated metal-organic framework click-grafting aptamers functionalized fabric for highly-specific recognition of microcystin-leucine arginine

Fabricating functional electrospun nanofiber coating for highly selective extraction of microcystin-LR (MC-LR) was of significant importance for water-safety monitoring. Herein, a novel MOF@aptamer functionalized nanofabric was presented via a facile and reliable strategy integrating polydopamine (PDA) mediation and thiol-ene chemistry and applied for specific recognition of the MC-LR model analyte. Using polydopamine (PDA) as the mediating layer, vinyl-UiO-66 MOF was grown in situ, followed by post-synthetic modification (PSM) of Zr⁴⁺ with vinyl phosphate and rapid UV-initiated click reaction of aptamers. Uniform deposition of Zr-based MOF (vinyl-UiO-66) on the nanofibers was directly produced, and the tedious co-electrospinning process was abandoned to prevent the aggregation and encapsulation of MOF. Via an efficient "thiol-ene" chemistry, massive thiol-terminated aptamers were grafted on MOF within one step under friendly conditions, rather than the time-consuming nanoparticle adsorption or unfriendly covalent chemical reactions. As a result, the robust MOF@aptamer-coated nano-fabrics were obtained, and a highly selective performance towards MC-LR was illustrated with a limit of detection (LOD) at 0.002 ng/mL, good precision (CV<8.3%), good repeatability (2.2∼6.0%) when coupled with LC-MS. Almost 1∼2 orders of magnitude higher detection sensitivity was exhibited than that of the common non-specific SPE/SPME fiber reported so far. Applied to water samples, the good matrix-resistance ability, and acceptable recovery yields were achieved with high specificity. This strategy might provide a rapid and friendly protocol to efficiently fabricate MOF@aptamer functionalized nano-fabrics through electrospinning and interfacial "thiol-ene" chemistry for highly-selective microextraction.

Combination of a dispersive solid phase extraction method based on octadecylamine modified magnetic nanoparticles with dispersive liquid-liquid microextraction for the extraction and preconcentration of pesticides

In the present work, a new and efficient sorbent has been prepared using the co-precipitation method for magnetic dispersive solid phase extraction followed by dispersive liquid-liquid microextraction. This method was used for the extraction and preconcentration of some widely-used pesticides (chlorpyrifos, haloxyfop-R-methyl, oxadiazon, diniconazole, clodinafop-propargyl, fenpropathrin, and fenoxaprop-P-ethyl) from fruit juices prior to their determination by gas chromatography-flame ionization detection. The sorbent was prepared by octadecylamine co-precipitation with Fe₃O₄. In the first step, mg amount of the magnetic sorbent was spread into an aqueous sample solution including the selected analytes and vortexed. Then the analytes were eluted with acetonitrile from the surface of the nanoparticles separated with an external magnetic field from the aqueous solution. In the second step, the obtained eluent was mixed with an extraction solvent (chloroform) at the μL-level and rapidly injected into deionized water. After centrifugation, an aliquot of the sedimented phase was injected into the separation system. Experimental parameters which control the performance of both steps were investigated and optimized. Using optimum extraction conditions, the proposed method provided low limits of detection (0.23-0.41 μg L^-1) and quantification (0.81-1.3 μg L^-1), high enrichment factors (353-443), acceptable extraction recoveries (70-88%), and satisfactory relative standard deviations (≤6%) for intra- (n = 6) and inter-day (n = 4) precisions at a concentration of 30 μg L^-1 of each pesticide.

Magnetic dispersive solid phase extraction of some polycyclic aromatic hydrocarbons from honey samples using iron (III) oxinate nanocomposite as an efficient sorbent

In this work, iron (III) oxinate magnetic nanocomposite was synthesized and employed as an efficient sorbent for the magnetic dispersive solid phase extraction of some polycyclic aromatic hydrocarbons from honey samples. In the following, dispersive liquid-liquid microextraction procedure was used to further preconcentration of the analytes. The prepared sorbent was characterized using Fourier transform infrared spectrophotometer, X-ray diffractometer, vibrating sample magnetometer, energy dispersive X-ray spectroscope, and scanning electron microscope. The results verified the successful formation of the magnetic sorbent. In the extraction process, the sorbent was added into an aqueous solution and the mixture was vortexed. After completing the adsorption process, the supernatant phase was separated in the presence of a magnet and the analytes adsorbed onto sorbent were eluted by acetonitrile. Then, μL-level of 1,1,1-trichloroethane was mixed with the obtained acetonitrile and injected into NaCl solution. Finally, one microliter of the sedimented phase was injected into gas chromatography-flame ionization detector after centrifugation. Under the optimum conditions, a great repeatability (relative standard deviation equal or less than 5 and 6% for intra- and inter day precisions, respectively), acceptable extraction recoveries (59-84%), high enrichment factors (118-168), and low limits of detection and quantification (0.16-0.36 and 0.56-1.22 ng g^-1 , respectively) were acquired. This article is protected by copyright. All rights reserved.

Magnetic graphene oxide-ultrathin nickel–organic framework composite for the extraction and determination of epoxiconazole in food samples

In this work, a magnetic graphene oxide-ultrathin metal–organic framework composite (Fe₃O₄@SiO₂-GO-Ni-MOF) was synthesized for the first time. Employing Fe₃O₄@SiO₂-GO-Ni-MOF composite as extractant, a novel method for the separation and analysis of the pesticide epoxiconazole was established with the assistance of high performance liquid chromatography (HPLC). The adsorption mechanisms were studied including by adsorption kinetics, thermodynamic parameters and adsorption isotherms. The experimental results showed that this method was convenient, operable, effective and practical for the extraction and determination of epoxiconazole in real samples.

Schematic illustration for the MSPE procedures.