Enrichment of phenolic compounds from water samples by using magnetic Fe3O4 nanoparticles coated with a Keggin type heteropoly acid of type H6[BFe(OH2)W11O39] as a sorbent

Polyoxometalate-based materials in extraction, and electrochemical and optical detection methods: A review

Polyoxometalates (POMs) as metal-oxide anions have exceptional properties like high negative charges, remarkable redox abilities, unique ligand properties and availability of organic grafting. Moreover, the amenability of POMs to modification with different materials makes them suitable as precursors to further obtain new composites. Due to their unique attributes, POMs and their composites have been utilized as adsorbents, electrodes and catalysts in extraction, and electrochemical and optical detection methods, respectively. A survey of the recent progress and developments of POM-based materials in these methods is therefore desirable, and should be of great interest. In this review article, POM-based materials, their properties as well as their identification methods, and analytical applications as adsorbents, electrodes and catalysts, and corresponding mechanisms of action, where relevant, are reviewed. Some current issues of the utilization of these materials and their future prospects in analytical chemistry are discussed.

A nanohybrid composed of polyoxotungstate and graphene oxide for dispersive micro solid-phase extraction of non-steroidal anti-inflammatory drugs prior to their quantitation by HPLC

A nanohybrid was prepared from polyoxotungstate anion and graphene oxide (POT/GO) and characterized in terms of porosity by applying Fourier transform infrared and transmission electron microscopy. The nanohybrid was applied as a sorbent for the dispersive micro solid-phase extraction of the non-steroidal anti-inflammatory drugs (NSAIDs) ibuprofen, diclofenac, and naproxen. Different types of sorbents were compared, and the POT/GO nanohybrid was found to have the best adsorption affinity. The NSAIDs were quantified via HPLC with UV detection. Under the optimum conditions, the limits of detection (at an S/N ratio of 3) range between 0.02-0.03 ng.mL^-1, and the linear response ranges extend from 0.08-200 ng.mL^-1, respectively. The relative standard deviations (RSDs) for five replicates at three concentration levels (0.1, 5 and 100 ng.mL^-1) of NSAIDs ranged from 4.1 to 6.1%. The applicability of the method was confirmed by analyzing spiked real water samples, and satisfactory results were obtained, with recoveries between 95.6 and 99.6%. Graphical abstract Schematic representation of the polyoxotungstate/graphene oxide nanohybrid preparation.

A hybrid material composed of a polyoxometalate of type BeW12O40 and an ionic liquid immobilized onto magnetic nanoparticles as a sorbent for the extraction of organophosphorus pesticides prior to their determination by gas chromatography

The authors describe a method for the extraction of organophosphorus pesticides (OPPs) by using a magnetically separable sorbent consisting of a polyoxometalate of type BeW₁₂O₄₀ supported on imidazole functionalized silica-coated cobalt ferrite. The sorbent was characterized by X-ray powder diffraction, field-emission scanning electron micrographs, vibrating sample magnetometry and FT-IR. The effects of the amount of adsorbent, pH value, salt concentration, extraction time, desorption solvent nature and volume and desorption time were investigated. Under optimal conditions, the method resulted in the following figures of merit: (a) the linear parts of the calibration plots typically extend from 0.08 to 300 μg mL^-1 of OPPs; (b) detection limits are between 0.02 to 0.06 ng mL^-1; and (c), extraction recoveries from spiked samples vary from 70.0 to 89.2%, with relative standard deviations between 5.4 and 7.6%. The nanocomposites can be reused up to 10 times. Compared to other methods for pretreatment and preconcentration of OPPs, the new method is more rapid, sensitive, accurate and eco-friendly. The method was successfully applied to the determination of the OPP residues in water samples and fruit juices. Graphical Abstract Schmatic presenation of the synthesis of core-shell magnetic nanoparticles (MNPs) of the type BeW12O40-ILSCCFNPs, and their application as sorbent for magnetic solid-phase extraction (MSPE) of organophosphorus pesticides.