In situ immobilization of layered double hydroxides onto cotton fiber for solid phase extraction of fluoroquinolone drugs

A Zn-MOF-based mixed matrix membrane as an ultrastable luminescent sensor for selective and visual detection of antibiotics and pesticides in food samples

The detection of antibiotics and pesticides are of great significance since their residues threaten the health of human beings by accumulation. However, most traditional solid chemical sensors are suffer from the limitations of low sensitivity and economic practicability because of the aggregating nature and unstable of solid sensors. Herein, a new luminescent sensor 1@PMMA (1, [(ZnL)·H2O]n (H2L = 5-(4-(pyridin-4-yl)benzamido)benzene-1,3-dioic acid); PMMA = poly(methyl methacrylate)) was successfully prepared. Notably, the polymer matrix provided the chemical protection for MOF particles. The as fabricated 1@PMMA was stable in milk, honey and egg as well as exhibited strong blue emission under ultraviolet light irradiation, which can act as luminescent probe for detecting antibiotics and pesticides. More interestingly, 1@PMMA exhibited visual, real-time and recyclable detection of antibiotics ornidazole (ODZ) and pesticides 2,6-dichloro-4-nitrobenzenamine (DCN) in real food samples. This work shows that the luminescent MOF-based mixed matrix membranes could be applied as good candidates for sensing analytes in practical application.

Zinc (Ⅱ) functionalized magnetic geopolymer as sorbents for rapid extraction of Fluoroquinolones in food prior to quantification by UHPLC-MS/MS

A novel Zn@MGeo sorbent was easily constructed and can bind with FQs through the synergistic effect of electrostatic interaction and coordination. With the Zn@MGeo as sorbent, a MSPE-UHPLC-MS/MS method was established for simultaneous detection of FQs in complex matrices. The whole extraction process could be completed using 6.0 mg sorbent within 10 min under the optimal conditions. The established quantitative method obtained a wide linear range (0.01-200 μg/kg, R² > 0.9987), high sensitivity (LODs: 0.005-0.05 μg/kg) and negligible matrix effect. The method was applied for analysis of real samples, with recoveries between 75.6% and 103.7%. In addition, the sorbent could be reused at least 9 times without reducing the adsorption performance. In general, the established method not only proposes a novel sorbent for FQs extraction, but also provides a powerful tool for rapid and sensitive detection of FQs in food matrices with practical application value.

Progress in pre-treatment and extraction of organic and inorganic pollutants by layered double hydroxide for trace-level analysis

Continuous release of pollutants into the environment poses serious threats to environmental sustainability and human health. For trace-level analysis of pollutants, layered double hydroxide (LDH) is an attractive option to impart enhanced sorption capability and sensitivity toward pollutants because of its unique layered structure, tunable interior architecture, high anion-exchange capacities, and high porosity (e.g., Zn/Cr LDH/DABCO-IL, Ni/Al LDH, CS-Ni/Fe LDH, SDS-Fe₃O₄@SiO₂@Mg-Al LDH, Boeh/Mg/Al LDH/pC, and Fe@NiAl LDH). In concert with the well-defined analytical methodologies (e.g., HPLC and GC), the LDH materials can be employed to detect trace-level targets (e.g., as low as ∼ 20 fg/L for phenols) in aqueous environments. This review highlights LDH as a promising material for pre-treatment of a variety of organic and inorganic target pollutants in complex real matrices. Challenges and future requirements for research into LDH-based analytical methods are also discussed.

Ferric iron loaded porphyrinic zirconium MOFs on corncob for the enhancement of diuretics extraction

Herein, corncob waste was used as a scaffold for the fabrication of effective adsorbents. Porphyrinic zirconium metal-organic frameworks (MOFs) PCN-223 and PCN-224 constructed by different numbers of Zr6 cluster nodes were grown on the surface of the corncob. Fe (Ш) ions were implanted in the porphyrin ring by post-synthesis modification. The results showed that the extraction capacity of diuretics on PCN-224@corncob containing suitable pore size was larger than that of PCN-223@corncob. The adsorption of diuretics was further enhanced because of the electrostatic effect caused by implantation of Fe (Ш) ions. PCN-224-Fe@corncob was recyclable and selective for the extraction of furosemide (Fur) and bumetanide (Bum). Coupled in-syringe solid phase extraction (IS-SPE) with ultra-performance liquid chromatography (UPLC), an efficient, sensitive, and stable method was established. With a sensitivity between 0.6 and 1.0 μg/L and a recovery between 83.2% and 119.2%, it is used for the analysis of trace amounts of Fur and Bum in weight loss products and environmental water. The functionalized corncob has potential application for the adsorption of diuretics, and the metal ions implantation in MOFs provides a promising strategy for enhancing extraction capacity.

Covalent Organic Framework/Polyacrylonitrile Electrospun Nanofiber for Dispersive Solid-Phase Extraction of Trace Quinolones in Food Samples

The extraction of quinolone antibiotics (QAs) is crucial for the environment and human health. In this work, polyacrylonitrile (PAN)/covalent organic framework TpPa–1 nanofiber was prepared by an electrospinning technique and used as an adsorbent for dispersive solid-phase extraction (dSPE) of five QAs in the honey and pork. The morphology and structure of the adsorbent were characterized, and the extraction and desorption conditions for the targeted analytes were optimized. Under the optimal conditions, a sensitive method was developed by using PAN/TpPa–1 nanofiber as an adsorbent coupled with high-performance liquid chromatography (HPLC) for five QAs detection. It offered good linearity in the ranges of 0.5–200 ng·mL⁻¹ for pefloxacin, enrofloxacin, and orbifloxacin, and of 1–200 ng·mL⁻¹ for norfloxacin and sarafloxacin with correlation coefficients above 0.9946. The limits of detection (S/N = 3) of five QAs ranged from 0.03 to 0.133 ng·mL⁻¹. The intra-day and inter-day relative standard deviations of the five QAs with the spiked concentration of 50 ng·mL⁻¹ were 2.8–4.0 and 3.0–8.8, respectively. The recoveries of five QAs in the honey and pork samples were 81.6–119.7%, which proved that the proposed method has great potential for the efficient extraction and determination of QAs in complex samples.

Fabrication of Magnetic Al-Based Fe3O4@MIL-53 Metal Organic Framework for Capture of Multi-Pollutants Residue in Milk Followed by HPLC-UV

The efficient capture of multi-pollutant residues in food is vital for food safety monitoring. In this study, in-situ-fabricated magnetic MIL-53(Al) metal organic frameworks (MOFs), with good magnetic responsiveness, were synthesized and applied for the magnetic solid-phase extraction (MSPE) of chloramphenicol, bisphenol A, estradiol, and diethylstilbestrol. Terephthalic acid (H₂BDC) organic ligands were pre-coupled on the surface of amino-Fe₃O₄ composites (H₂BDC@Fe₃O₄). Fe₃O₄@MIL-53(Al) MOF was fabricated by in-situ hydrothermal polymerization of H₂BDC, Al (NO₃)₃, and H₂BDC@Fe₃O₄. This approach highly increased the stability of the material. The magnetic Fe₃O₄@MIL-53(Al) MOF-based MSPE was combined with high-performance liquid chromatography-photo diode array detection, to establish a novel sensitive method for analyzing multi-pollutant residues in milk. This method showed good linear correlations, in the range of 0.05–5.00 μg/mL, with good reproducibility. The limit of detection was 0.004–0.108 μg/mL. The presented method was verified using a milk sample, spiked with four pollutants, which enabled high-throughput detection and the accuracies of 88.17–107.58% confirmed its applicability, in real sample analysis.

Carbon fibers as green and sustainable sorbent for the extraction of isoflavones from environmental waters

Isoflavones are a group of phytoestrogens of important environmental concern due to their endocrine disrupting effects. This article presents a rapid, green, and sustainable method for determining four isoflavones (daidzein, genistein, formononetin, and biochanin A) in environmental waters complying with current trends in Analytical Chemistry. The method consists of in-syringe dispersive solid-phase extraction (DSPE) as the extraction approach, using carbon fibers as extraction material. The synthesis of carbon fibers is simple and sustainable, since it only requires a natural product such as raw cotton as precursor, which is thermally treated (600 °C for 30 min) in an inert (Ar) atmosphere to convert it into carbon fibers. After extraction, the final eluate is analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The proposed methodology allows the determination of the four isoflavones in water samples at the ng L^-1 range, with limits of detection in the range from 17 to 25 ng L^-1, relative standard deviations (RSD) from 2.8 to 10.1%, and good batch-to-batch repeatability (RSD < 13%). The method was finally applied to six environmental water samples from different sources and two swimming pool waters, and concentrations of all analytes up to 490 ng L^-1 were found. The highest concentrations were found in those samples close to crop fields. Relative recovery values (80-121%) showed that the aqueous matrices considered in this work did not significantly affect the extraction process. This method overcomes the drawbacks of the previous works with the same purpose, such as consuming large volumes of organic solvents or prolonged extraction times. Moreover, this procedure would allow the extraction stage to be carried out in situ, since only the sorbent material (previously synthesized in the laboratory) and disposable syringes are required.

Determination of seven tetracyclines in milk by dissolvable layered double hydroxide-based solid-phase extraction coupled with high-performance liquid chromatography

A dissolvable layered double hydroxide-based solid-phase extraction combined with high-performance liquid chromatography was developed for the analysis of minocycline, oxytetracycline, tetracycline, demeclocycline, metacycline, chlortetracycline and doxycycline in milk samples. In situ formation of the layered double hydroxide was achieved by the addition of MgCl₂-AlCl₃ solution to alkaline deproteinized milk. The analytes were efficiently extracted by the Mg/Al layered double hydroxide. After centrifugation, the co-precipitates were dissolved in 0.1 mol L^-1 Na₂EDTA-McIlvaine buffer prior to HPLC analysis. Under optimized conditions, the method achieved low detection limits of 0.414-0.986 μg L^-1 and quantification limits of 1.38-3.29 μg L^-1, and good recoveries of 93.5-100% with intra- and inter-day RSDs of 0.498-4.08% and 1.23-10.0%, respectively. This method is convenient, accurate, sensitive, rapid, cost-effective, eco-friendly, and suitable for the determination of seven tetracycline antibiotics in milk samples.

Ionic Liquid-Functionalized Magnetic Metal-Organic Framework Nanocomposites for Efficient Extraction and Sensitive Detection of Fluoroquinolone Antibiotics in Environmental Water

Herein, the hydrophobic carboxyl-functionalized ionic liquid (IL-COOH) was encapsulated into the prepared Fe₃O₄@Zr-MOFs, and the novel water-stable IL-COOH/Fe₃O₄@Zr-MOF nanocomposites were first synthesized. The polydopamine-functionalized Fe₃O₄ was introduced to construct the core-shell structure via layer-by-layer modification, and the controlled growth of Zr-MOFs was achieved, which realized the adjustment of charged properties of nanocomposites and simplified the adsorption or extraction process. The IL-COOH/Fe₃O₄@Zr-MOFs were fully studied by IR, HNMR, XRD, N₂ adsorption-desorption isotherms, TEM, EDS mapping, VSM, and so on. Then, they were employed for the selective adsorption and detection of fluoroquinolone antibiotics (FQs). The adsorption isotherms and kinetics demonstrated that the adsorption process followed a pseudo-second-order kinetic model and the Langmuir isotherm model. Among them, IL-COOH/Fe₃O₄@UiO-67-bpydc showed the best adsorption performance, and the maximum adsorption capacity of ofloxacin was 438.5 mg g^-1. Coupled magnetic solid-phase extraction with HPLC-DAD, a convenient, sensitive, and efficient method for extraction and detection of FQs in environmental water, was developed based on IL-COOH/Fe₃O₄@UiO-67-bpydc. The recoveries of environmental water were ranging from 90.0 to 110.0%, and the detection limits were lower than 0.02 μg L^-1. The novel functionalized composites served as solid-phase adsorbents and liquid-phase extractants. This study also provided a promising strategy for designing and preparing multi-functionalized nanocomposites for the removal or detection of pollutants in environmental samples.

RETRACTED: Preparation of molecularly imprinted metal-organic frameworks by in situ self-assembly template strategy for selective adsorption of antibiotics

This article has been retracted: please see Elsevier Policy on Article Withdrawal ( https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Authors. The corresponding author informed the journal that there were severe problems with the testing instrument that rendered the subsequent conclusions invalid. The authors apologise for any inconvenience caused.

Surface area expansion by flower-like nanoscale layered double hydroxides for high efficient stir bar sorptive extraction

Enhancing the surface area of stationary phase is essential in chromatographic science. In this work, nanoscale NiAl-layered double hydroxides (NiAl-LDHs) with flower-like structure was used as a platform for supporting the stationary phase. Then strong hydrophobic p-naphtholbenzein molecule was immobilized onto the LDHs layer as sorbent for stir bar sorptive extraction (SBSE). The flower-like LDHs layer significantly increased the extraction efficiency through increasing the specific surface area and immobilized amounts of stationary phase. In addition, the LDHs can also provide anion exchange ability, which expanded the application of this stir bar for analysis of not only hydrophobic but also anionic analytes. For improving the workability, a poly(ether ether ketone) (PEEK) jacket stir bar with detachable dumbbell-shaped structure was employed. The PEEK jacket with high mechanical strength and dumbbell-shaped structure improved the durability of stir bar and the detectable design allowed elution to be realized with less solvent that enhanced the enrichment factor. The proposed stir bar showed good performance for the extraction of multiple analytes including flavonoids, non-steroid anti-inflammatory drugs and chlorophenoxy acids. By coupling with high performance liquid chromatography-ultraviolet detection (HPLC-UV), the SBSE-HPLC-UV method was applied for the extraction of three active components including bavachin, isobavachalcone and bavachinin in Psoralea corylifolia L. herb with low limit detection of 0.01-0.02 ng/mL.

Recent advances in the application of layered double hydroxides in analytical chemistry: A review

In recent years, layered double hydroxides (LDHs) have garnered a lot of attention in analytical chemistry, due to their advantages such as relatively simple synthesis, low cost, possession of large specific surface area and high catalytic activity, and biocompatibility. The most common applications of LDH in analytical chemistry such as sorbents in sample extraction, electrode materials in electrochemical sensing and color indicators in colorimetric detection have been well reported. Generally, the LDHs are prepared as composites with nanomaterials, or constructed with specific three-dimensional structures, befitting the applications desired for them. However, the applications of LDHs (as extraction sorbents, color indicators and in electrochemical sensing) are usually limited in these scenarios. To help address these challenges, future trends and developmental prospects of LDHs materials in analytical chemistry are discussed in this article. Besides, the strategies associated with the design of LDHs, including the structural aspects, for potential analytical applications are presented and reviewed.

Investigations of structural, spectral and electronic properties of enrofloxacin and boron complexes via quantum chemical calculation and molecular docking

Quantum chemical analyses were performed over enrofloxacin and boron complexes. The most stable isomer of enrofloxacin was examined at M062X/6-31+G(d) level in gas phase. Structural and spectral characterizations of enrofloxacin and its complexes were performed at same level of theory. MEP maps of studied compound were calculated via ESP charges analyses. Some quantum chemical descriptors (QCDs) were calculated to determine the non-linear optical (NLO) and biological reactivity of studied molecules. Furthermore, molecular docking calculations between boron complexes and a protein (ID: 2ITN and 2ITV) were done. ADME analyses were done in the determination of the best drug candidate. As a result, complex (3) was found as the best in the NLO applications and it was found that complex (1) and (3) have similar biological reactivity in lung cancer treatment.