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Zeolitic imidazolate frameworks (ZIFs) consist of metal nodes connected to imidazolate linkers, having both the properties of metal-organic frameworks (MOFs) and inorganic zeolites, such as controllable pore sizes, high porosity and surface areas, as well as exceptional thermal and chemical stability, thereby making them a class of attractive materials for diverse analytical applications. In this study, we reported a facile magnetization process of ZIF-7 (zinc benzimidazolate) for simultaneous magnetic extraction of polycyclic aromatic hydrocarbons (PAHs) by simply mixing ZIF-7 and polydopamine (PDA)-coated Fe3O4 nanoparticles (PDA@Fe3O4) in solutions. Functional groups (-OH and -NH2), provided by PDA as a highly efficient molecular linker, could attract and anchor ZIF-7 through noncovalent adsorption and covalent cross-link interactions, thereby promoting the complete magnetization of ZIFs and enhancing their stability and reusability. The bridging ligand benzimidazolate, could be bonded with PAHs because of its high surface area, large pores, accessible coordinative unsaturated sites (π-complexation), and π-π stacking action. This ZIF-based magnetic solid-phase extraction (SPE), coupled with gas chromatography/tandem mass spectrometry (GC/MS), was further evaluated for analysis of PAHs from rainwater and air samples of particulate matter less than 2.5μm in diameter (PM2.5). The main effective parameters, including ionic strength, solution pH, extraction time, desorption solvent and desorption time, were investigated, respectively. Under optimized conditions, the developed method based on Fe3O4@PDA/ZIF-7 gave detection limits of 0.71-5.79ng/L, and quantification limits of 2.50-19.2ng/L for PAHs, respectively. The relative standard deviations for intra-day and inter-day analyses were in the range of 3.1-9.1% and 6.1-12.7%, respectively. The PAHs founded in PM2.5 were in the range of 0.40-6.79ng/m(3). Good recoveries (>82%) with low relative standard deviations (≤9.2%) were achieved. This method was demonstrated to be an accurate, convenient and sensitive pretreatment procedure for trace analysis of environmental water and air samples., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this study, magnetic pomelo peel‐derived biochar composite was fabricated and applied as a low‐cost adsorbent for the simultaneous extraction of morphine‐like opioids named morphine, codeine, and 6‐monoacetylmorphine from wastewaters, prior to their determination via liquid chromatography‐mass spectrometry. A total of four biochar products were synthesized under different pyrolytic temperatures of 400, 500, 600, and 700°C, respectively, and the 400°C biochar was found to have the greatest extraction ability, with enrichment factors of 34, 58, and 61 for the three drugs. The primary adsorption mechanism includes π‐π interaction and H‐bonding. Parameters affecting the extraction of opioids were optimized. Under optimum conditions (such as pH = 7; adsorbent amount = 15 mg; sample volume = 20 ml; eluent solvent, 200 µl of methanol), the method was proved to be linear in the range of 0.05–10.0 µg/L, with coefficients of determination greater than 0.99, and the limits of detection were 0.006–0.010 µg/L. In‐batch and inter‐batch precisions were 1.8%–6.5% and 4.8%–10.6%, respectively. The method was successfully applied to the determination of the target opioids in the samples of influent and effluent wastewater. The developed method by using magnetic pomelo peel‐derived biochar could potentially be applied for the effective estimation of illicit drug consumption. [ABSTRACT FROM AUTHOR]

Abstract: In this study, an alternative method for synthesizing magnetic cobalt adeninate metal–organic frameworks was developed, and the synthesized materials were examined for their potential application for separating and enriching benzodiazepines from complex samples. Benzodiazepines, widely used as hypnotics, muscle relaxants, sedatives, and anxiolytics, are a class of drugs that require accurate detection and monitoring. Results showed that Fe3O4 nanoparticles could be well anchored onto the external surface of cobalt adeninate metal–organic frameworks by using amino‐silane as a linkage. Their adsorption of benzodiazepines was mainly promoted by intermolecular hydrogen binding, π–π interactions and electrostatic attraction. Their potential application was evaluated by extraction of benzodiazepines in urine and wastewater samples prior to liquid chromatography with mass spectrometry. Under optimum conditions, the calibration curves were linear with a correlation coefficient of ≥0.9928 in the concentration range of 10–5000 ng/L for lorazepam and 5–5000 ng/L for estazolam, chlordiazepoxide, alprazolam, midazolam and triazolam. The limits of detection were in the range of 0.71–2.49 ng/L. The percent of extraction recoveries were 80.2–94.5% for urine and 84.1–94.4% for wastewater, respectively. Results suggested that magnetic cobalt adeninate metal–organic frameworks could potentially be a promising material for enriching benzodiazepines from urine and wastewater with high accuracy and precision. [ABSTRACT FROM AUTHOR]

An active magnetic metal-organic framework (MOF) hybrid material was prepared using a novel in situ solvothermal method in the presence of magnetite (Fe 3 O 4 ) particles, that holds much promise for large-scale synthesis. MIL-101(Fe), an iron terephthalate with pore structure and high resistance to water and common solvents, was functionalized as a model with superparamagnetic qualities, using Fe 3 O 4 . The electrostatic interaction between Fe 3 O 4 and metal ions was thereby used to chemically stabilize magnetic nanoparticles, and thus MOF crystals were uniformly enclosed by Fe 3 O 4 to form a homogeneous magnetic product identified as a Fe 3 O 4 /MIL-101 composite. This hybrid material with magnetic susceptibility but with the lowest possible loading amount of Fe 3 O 4 was examined, and its potential application for magnetic solid-phase extraction of six organophosphorus pesticides (OPPs) from human hair and urine samples, followed by gas chromatography analysis, was assessed. The main effect parameters including solution ionic strength, desorption solvent, extraction time and desorption time were investigated in sequence. Under optimized conditions, this method showed low detection limits (0.21–2.28 ng/mL), wide linearity, and good precision (1.8–8.7% for intra-day, 2.9–9.4% for inter-day). The matrix interference produced by hair or urine could be effectively eliminated using this method, and satisfactory recoveries of the spiked samples were 76.8–94.5% and 74.9–92.1%, respectively, indicating that the Fe 3 O 4 /MIL-101 sorbents are feasible for the analysis of trace analytes from biological samples. [ABSTRACT FROM AUTHOR]

• Spin column extraction (SCE) for OPPs. • A polydopamine@polymer monolith in spin column was prepared. • The monolith exhibited enhanced adsorption affinity towards OPPs. • Excellent permeability, stability and reusability of the monolith. • SCE was successfully applied for fast and simple analysis of OPPs in urine. The determination of organophosphorus pesticides in urine is useful for evaluating human exposure. In this study, a simple micro-solid-phase extraction method based on a polydopamine-modified monolithic spin column combined with liquid chromatography–mass spectrometry (LC-MS) was developed for the determination of six organophosphorus pesticides (dimethoate , dichlorvos, carbofuran, methidathion, phosalone, and chlorpyrifos) in urine samples. A methacrylate polymer monolithic support was prepared in situ in the spin column, and dopamine solution was repeatedly passed through the monolith matrix via centrifugation to generate a polydopamine layer in the polymeric network. All extraction steps were performed via centrifugation. The monolith exhibited good permeability, which enabled high-flow-rate sample loading and significantly reduced the sample pre-treatment time. The addition of polydopamine significantly improved the extraction efficiency of the monolithic spin column owing to the catechol and amine groups in dopamine, which can enhance hydrogen bonding and π–π stacking. Factors affecting the extraction, including the solution pH, centrifugation speed, and desorption solvent, were investigated to determine the optimal extraction conditions. Under the optimal conditions, the OPP detection limits were 0.02–1.32 µg/L. The relative standard deviations of the single column (n = 5) and column-to-column (n = 3) precision for the extraction method were <11%. The monolithic spin column exhibited high stability and could be used for more than 40 extraction cycles. The recoveries for spiked urine samples were 72.1–109.3% (RSDs: 1.6–7.9%). The developed method was successfully applied to the simple and rapid analysis of organophosphorus pesticides in urine samples. [ABSTRACT FROM AUTHOR]