Development of doubly porous composite adsorbent for the extraction of fluoroquinolones from food samples

Natural deep eutectic solvent-based hollow polymer inclusion membrane doped with TiO2 nanoparticles: A new design of polymer inclusion membrane for on-chip electromembrane extraction of fluoroquinolones from food samples prior to liquid chromatography tandem mass analysis

A new design of polymer inclusion membrane has been proposed with the aim of addressing issues with using common forms of liquid membranes. To do so, a natural deep eutectic solvent (NADES) was employed as an extractant in the structure of the hollow polymer inclusion membrane (HPIM). Besides polyvinyl chloride (PVC) as a base polymer, titanium dioxide nanoparticles (TiO2) as well as polyethylene glycol polymer (PEG) were incorporated into the HPIM structure to achieve a nanocomposite form with a desirable hydrophilicity. The optimal HPIM was composed of 12.5 v/w% of thymol-coumarin NADES, 3.0 w/w% of TiO2 and 40.0 v/w% of PEG based on PVC content. Aiming to compare the applicability, HPIMs with other types of extractants, such as bis(2-ethylhexyl) phthalate (DEHP), and the mixture of DEHP-NADES were also fabricated. To confirm the successful fabrication of the HPIM, containing the aforementioned extractant doped with TiO2 nanoparticles various characterization techniques were employed. The resultant HPIM was employed as a liquid membrane in an on-chip electromembrane extraction (EME) of fluoroquinolones (FQs) from various samples, followed by LC-MS/MS analysis. The parameters influencing extraction performance were analyzed, and the proposed method was validated under ideal conditions. All the samples provided excellent performance concerning limits of detection (0.01-0.08 ng mL-1), and quantification (0.03-0.25 ng mL-1) together with an excellent linearity (R2 ≥ 0.9978). The method indicates the desirable RSDs% in the range of 3.2-7.0 % (intra-day, n = 3 × 3) and 3.8-6.1 % (inter-day, n = 3 × 3) for three spiked levels. The satisfactory relative recoveries fell within the 92.0-115.0 % range.

Cationic conjugated microporous polymers for efficient quinolone antibiotics extraction: Experimental and DFT study

The development of exquisitely sensitive analytical methods for the surveillance of quinolone antibiotics (QAs) holds pivotal significance in safeguarding both ecosystems and human well-being. In this work, a cationic conjugated microporous polymer (iCMP) was constructed through a facile post-synthetic approach. Capitalizing on its unique dual-porosity architecture, cationic framework, and π-conjugated backbone, iCMP exhibited exceptional adsorption capabilities and remarkable repeatability. Integrating with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), a solid-phase extraction (SPE) method founded on iCMP was meticulously developed for the sensitive and accurate detection of QAs within complex matrices. This proposed analytical method exhibited remarkably low limits of detection, specifically 0.0200-0.128 ng·L-1 for water samples and 0.0250-0.105 ng·g-1 for meat samples, along with good accuracy in the range of 70.9 %-115 %. The underlying adsorption mechanism was comprehensively investigated using a synergistic approach that combined systematic adsorption experiments, density functional theory (DFT) calculations, and in-depth material characterizations. Overall, this study presents viable strategies for the precise trace-level analysis of QAs in complex environmental and food samples.

Calixarene incorporated molecular imprinting on covalent organic framework for supramolecular recognition and specific extraction of citrinin

Specific recognition and selective extraction of mycotoxin in environmental and food matrixes is significant to guarantee public health. Covalent organic frameworks (COFs) are promising adsorbents with tailorable functionality, but their low binding affinity and poor selectivity hamper their wide application for selective extraction of trace mycotoxin from complex matrix. Herein, we report calixarene incorporated molecular imprinting on COF to prepare molecularly imprinted calix[4]arene-containing COF (MICOF-CX4) for supramolecular recognition and specific adsorption of citrinin. Calixarene with host-guest chemistry was used as a functional monomer, while amine units with different topologies and function groups were selected to regulate MICOF-CX4 to match with citrinin. The complementary shape and supramolecular interactions of MICOF-CX4 gave highly selective recognition for citrinin. Moreover, MICOF-CX4 with vast accessible surface and plentiful imprinting sites exhibited faster adsorption kinetics and 4-fold higher adsorption capacity for citrinin adsorption than no-imprinted COF-CX4. Combination of MICOF-CX4 based solid-phase extraction with high-performance liquid chromatography-mass spectrometry allowed interference free determination of trace citrinin in real samples with a low detection limit of 0.03 ng mL-1, good precision of 4.5 % and quantitative recovery of 88.2 %-101.4 %. The cooperative functions of calixarene and molecular imprinting make COF promising adsorbent for specific adsorption of trace targets in complex matrixes.

Hydroxyl-containing triazine-based conjugated microporous polymers for solid phase extraction of fluoroquinolone antibiotics in the environment and food samples

Fluoroquinolones (FQs) are a category of broadly used antibiotics. Development of an effective and sensitive approach for determination of trace FQs in environmental and food samples is still challenging. Herein, the hydroxyl-containing triazine-based conjugated microporous polymers (CMPs-OH) was constructed and served as SPE absorbent for the efficient enrichment of FQs. Based on DFT simulations, the excellent enrichment capacity between CMPs-OH and FQs was contributed by hydrogen bonding and π-π interactions. In combination with high-performance liquid chromatography-tandem mass spectrometry, the proposed approach exhibited a wide linear range (0.2-400 ng L-1), low detection limits (0.05-0.15 ng L-1), and good intraday and interday precisions under optimal conditions. In addition, the established method was effectively utilized for the determination of FQs in fourteen samples with recoveries between 82.6 % and 109.2 %. This work provided a feasible sample pretreatment method for monitoring FQs in environmental and food matrices.

Graphene oxide mediated CdSe quantum dots fluorescent aptasensor for high sensitivity detection of fluoroquinolones

In view of the urgent need for fluoroquinolones contamination detection in the fields of food safety, a novel aptasensor based on the fluorescence quenching property of graphene oxide (GO) and the fluorescence characteristic of cadmium selenide quantum dots (CdSe QDs) was developed for fluoroquinolones highly sensitive detection in this work. The CdSe QDs with carboxyl-rich surface were synthesized successfully and fluoresced at 525 nm under the optimal excitation light of 366 nm. Based on the hydrophobic and π-π stacking between GO and aptamer, aptamer labeled by CdSe QDs fluorescence (CdSe QDs-apt) were adsorbed by GO and the fluorescence of CdSe QDs was quenched. After the aptamer combined specifically with fluoroquinolones, greater specific force lead to the desorption of CdSe QDs-apt from GO and fluorescence recovery. Represented by Ciprofloxacin (CIP), a member of fluoroquinolones, the fluorescence emission increased with the increasing of CIP concentrations from 8 nM to 500 nM, and the detection limit was 0.42 nM. The spiked recoveries in real samples of honey and milk were 91.5-96.9 % and 90.3-95.2 %, respectively, indicating that the aptasensor was reliable. Moreover, the fluorescence responses of multiple members of fluoroquinolones were found to be consistent, denoting that the fluorescence aptasensor can be used to detect the total amount of multiple members of fluoroquinolones. These results showed that the aptasensor can be used as a promising platform for fluoroquinolones detection.

Sensitive electrochemical detection of enrofloxacin in eggs based on carboxylated multi-walled carbon nanotubes-reduced graphene oxide nanocomposites: Molecularlyimprintedrecognition versus direct electrocatalytic oxidation

A sensitive electrochemical method for detecting enrofloxacin was proposed using carboxylated multi-walled carbon nanotubes-reduced graphene oxide (MWCNT-COOH-RGO) nanocomposites. The MWCNT-COOH-RGO nanocomposites were firstly electrodeposited on a bare electrode, followed by electropolymerization of molecularly imprinted polymers. Enrofloxacin was determined by the mechanisms of direct electrocatalytic oxidation and molecularly imprinted recognition, respectively. Under the optimized conditions, a response range of 5.0×10^-7 M to 5.5×10^-5 M and limit of detection (LOD) of 2.3×10^-7 M were obtained by direct electrocatalytic oxidation of enrofloxacin using chronoamperometry. By contrast, the response range of 1.0×10^-10 M to 5.0×10^-5 M and LOD of 2.5×10^-11 M were achieved by molecularly imprinted recognition of enrofloxacin using square-wave voltammetry. Moreover, the proposed method exhibited good repeatability, stability and selectivity, and could be used for enrofloxacin detection in egg samples with satisfactory results.

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.

Polyaniline and Polyaniline-Based Materials as Sorbents in Solid-Phase Extraction Techniques

Polyaniline (PANI) is one of the best known and widely studied conducting polymers with multiple applications and unique physicochemical properties. Due to its porous structure and relatively high surface area as well as the affinity toward many analytes related to the ability to establish different types of interactions, PANI has a great potential as a sorbent in sample pretreatment before instrumental analyses. This study provides an overview of the applications of polyaniline and polyaniline composites as sorbents in sample preparation techniques based on solid-phase extraction, including conventional solid-phase extraction (SPE) and its modifications, solid-phase microextraction (SPME), dispersive solid-phase extraction (dSPE), magnetic solid-phase extraction (MSPE) and stir-bar sorptive extraction (SBSE). The utility of PANI-based sorbents in chromatography was also summarized. It has been shown that polyaniline is willingly combined with other components and PANI-based materials may be formed in a variety of shapes. Polyaniline alone and PANI-based composites were successfully applied for sample preparation before determination of various analytes, both metal ions and organic compounds, in different matrices such as environmental samples, food, human plasma, urine, and blood.

Sulfonic acid-functionalized covalent organic frameworks as the coating for stir bar sorptive extraction of fluoroquinolones in milk samples

Sulfonic acid-functionalized covalent organic frameworks (COF-SO₃) as a coating of stir bar sorptive extraction (SBSE) for capturing three fluoroquinolones from milk have been developed. The COF-SO₃ material was characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. Milk without any typical treatments like protein precipitation and defatting was only diluted five times with water for test. Combined with high-performance liquid chromatography (HPLC), a SBSE-HPLC method was established for detecting fluoroquinolones in milk samples. The corresponding wide linear ranges (4.00-500.0 µg L^-1), low detection limits (1.20-2.62 µg L^-1), good test repeatability (RSD < 5.2%), and acceptable enrichment factors (56.2-61.5) were implemented for three fluoroquinolones. The analytical method was applied to determine trace targets and provided satisfactory results. Furthermore, the research displayed satisfied reproducibility for bar-to-bar (RSD < 6.5%) and batch-to-batch (RSD < 8.6%) tests.

A novel terbium (III) and aptamer-based probe for label-free detection of three fluoroquinolones in honey and water samples

Fluoroquinolones, a family of synthetic broad-spectrum antibiotics, are widely used in clinical medicine, farm animals and aquaculture. Residues of fluoroquinolones in samples have attracted much attention because of growing food safety and public health concerns. Here, a novel Tb³⁺ ion-enrofloxacin aptamer coordination probe was prepared to develop a sensitive and rapid label-free fluorescence assay for specific detection three fluoroquinolones. In presence of the target, Tb³⁺ ion- enrofloxacin aptamer probe specifically bound with enrofloxacin, norfloxacin and ciprofloxacin, leading to a sharp increase in fluorescence emission of the probe. Under the optimized conditions, fluorescence increased linearly in the 1.0-100.0 ng/mL range for the three fluoroquinolones, with 0.053 ng/mL limit of detection for ciprofloxacin, 0.020 ng/mL limit of detection for norfloxacin and 0.061 ng/mL limit of detection for enrofloxacin. Satisfactory recovery (80.10-102.48%) in spiked honey and water samples were obtained for the three fluoroquinolones with relative standard deviations between 0.21% and 5.44% (n = 3).

Carbon nanostructures: a comprehensive review of potential applications and toxic effects

There is no doubt that nanotechnology has revolutionized our life since the 1970s when it was first introduced. Nanomaterials have helped us to improve the current products and services we use. Among the different types of nanomaterials, the application of carbon-based nanomaterials in every aspect of our lives has rapidly grown over recent decades. This review discusses recent advances of those applications in distinct categories, including medical, industrial, and environmental applications. The first main section introduces nanomaterials, especially carbon-based nanomaterials. In the first section, we discussed medical applications, including medical biosensors, drug and gene delivery, cell and tissue labeling and imaging, tissue engineering, and the fight against bacterial and fungal infections. The next section discusses industrial applications, including agriculture, plastic, electronic, energy, and food industries. In addition, the environmental applications, including detection of air and water pollutions and removal of environmental pollutants, were vastly reviewed in the last section. In the conclusion section, we discussed challenges and future perspectives.

Core-shell magnetic porous organic polymer for magnetic solid-phase extraction of fluoroquinolone antibiotics in honey samples followed by high-performance liquid chromatography with fluorescence detection

By monomer-mediated in-situ growth synthesis strategy, with hydroquinone and 1,3,5-tris(4-aminophenyl)benzene as monomers, a core-shell magnetic porous organic polymer was synthesized through a simple azo reaction. Based on this, a magnetic solid-phase extraction-high-performance liquid chromatography-fluorescence detection method was proposed for the analysis of fluoroquinolones in a honey sample. With ofloxacin, ciprofloxacin, enrofloxacin, lomefloxacin, and difloxacin as target analytes, factors affecting the extraction efficiency had been optimized. The LODs were 1.5-5.4 ng/L (corresponding to 0.23-0.81 μg/kg in honey). The linear range was 0.005-20 μg/L for difloxacin, 0.01-20 μg/L for ofloxacin, ciprofloxacin and lomefloxacin, and 0.02-20 μg/L for enrofloxacin. The enrichment factor was 84.4-91.7-fold with a high extraction efficiency of 84.4-91.7%. The method was assessed by the analysis of target fluoroquinolones in honey samples, and the recoveries for the spiked samples were 79.3-95.8%. The results indicated that the established magnetic solid-phase extraction-high-performance liquid chromatography-fluorescence detection method is efficient for the analysis of trace fluoroquinolones in honey.

Synthesis of molecularly imprinted polymers for extraction of fluoroquinolones in environmental, food and biological samples

In recent years, fluoroquinolones have been found present in important water resources and food sources which compromises the food quality and availability, thereby, causing risks to the consumer. Despite the recent advancement in the development of analytical instrumentation for routine monitoring of fluoroquinolones in water, food, and biological samples, sample pre-treatment is still a major bottleneck of the analytical methods. Therefore, fast, selective, sensitive, and cost-effective sample preparation methods prior to instrumental analysis for fluoroquinolones residues in environmental, food and biological samples are increasingly important. Solid-phase extraction using different adsorbents is one of the most widely used pre-concentration/clean-up techniques for analysis of fluoroquinolones. Molecularly imprinted polymers (MIPs) serve as excellent effective adsorbent materials for selective extraction, separation, clean-up and preconcentration of various pollutants in different complex matrices. Therefore, synthesis of MIPs remains crucial for their applications in sample preparation as this offers much-needed selectivity in the extraction of compounds in complex samples. In this study, the progress made in the synthesis of MIPs for fluoroquinolones and their applications in water, food and biological samples were reviewed. The present review discusses the selection of all the elements of molecular imprinting for fluoroquinolones, polymerization processes and molecular recognition mechanisms. In conclusion, the related challenges and gaps are given to offer ideas for future research focussing on MIPs for fluoroquinolones.

Inner-filter effect induced fluorescent sensor based on fusiform Al-MOF nanosheets for sensitive and visual detection of nitrofuran in milk

Developing highly sensitive and visual methods for rapid detection of antibiotics is significant to ensure food quality and safety. To meet the requirement of nitrofuran antibiotics detection, luminescent fusiform Al(III)-containing metal-organic frameworks (Al-MOF) nanosheets were successfully synthesized by one-step hydrothermal method. And then, the nanosheet served as a fluorescent probe to detect nitrofuran via the inner-filter effect mechanism. The developed sensor allowed sensitive and selective detection of nitrofuran with good linear relationships. And, the detection limit (LOD) values were estimated to be 0.53, 0.838 and 0.583 μM for nitrofurazone, nitrofurantoin and furazolidone detection, respectively. The practical application of the proposed system was verified by HPLC in spiked milk samples with satisfying recoveries ranging from 88.14 to 126.21% and low relative standard deviations of 2.85 ~ 8.13%. Moreover, we designed fluorescent test papers for semi-quantitative detection of nitrofuran via naked-eye colorimetric assay. The established method provides an alternative strategy for semiquantitative detection of nitrofuran.

Nanohybrid magnetic composite optosensing probes for the enrichment and ultra-trace detection of mafenide and sulfisoxazole

Nanohybrid magnetic optosensing probes were designed and fabricated to enrich and detect ultra-trace levels of mafenide and sulfisoxazole simultaneously. The probes combined the high affinity of MIL-101 and the sensitivity of graphene quantum dots (GQDs) and cadmium telluride quantum dots (CdTe QDs) with the selectivity and rapid separation provided by a magnetic molecularly imprinted polymer (MMIP). Since the MIL101-MMIP-GQD and MIL101-MMIP-CdTe QD probes produced high fluorescence emission intensities at 435 and 572 nm, respectively, mafenide and sulfisoxazole could be simultaneously detected. Quantitative analysis was based on fluorescence quenching produced by binding between target molecules and imprinted recognition cavities. In the optimal experimental condition, emission intensity was quenched linearly with increasing analyte concentration from 0.10 to 25.0 μg L^-1. Limit of detection was 0.10 μg L^-1 for mafenide and sulfisoxazole. The developed optosensor was applied to detect ultra-trace amounts of mafenide and sulfisoxazole in bovine milk. Recoveries of mafenide and sulfisoxazole in spiked bovine milk ranged from 80.4 to 97.9% with RSDs <5% and the analysis results agreed well with HPLC analysis. The proposed probes provided excellent sensitivity, selectivity, ease and convenience of use.

Immobilized imidazolium-based ionic liquids in C18 for solid-phase extraction

In this work, two solid-phases based on imidazolium-based ionic liquids were obtained and characterized for solid-phase extraction of fluoroquinolones. The process of immobilization was performed replacing a toxic reagent by UV-irradiation to get a harmless process. The obtained solid-phases were characterized by nuclear magnetic resonance spectroscopy and elemental analysis. Each solid-phase was packed in a cartridge and was used in solid-phase extraction processes for norfloxacin and ciprofloxacin, after the optimization of some parameters such as the elution solvent, the eluent volume and, the sample volume to be used during the loading step. The developed solid-phases with immobilized ionic liquids were successfully implemented for the studied compounds and indicate high probabilities to be useful in solid-phase extractions of other fluoroquinolones.

Colorimetric determination of amaranth followed enrichment and separation using buoyant adsorbents

A buoyant solid-phase extraction adsorbent was prepared by sodium alginate-coated hollow glass microspheres (HGMs) modified with 3-aminopropyltrimethoxysilane (3-APTS) for the separation and enrichment of anionic dye amaranth. After adsorbing amaranth, these low-density adsorbents can float on the surface of the solution, so the separation between adsorbents and substrates can be carried out by flotation. Quantitative determination of amaranth after separation and enrichment can be achieved by combining spectrophotometry. Under the optimum conditions, the linear range and detection limit for amaranth detection were 0.02 mg L−1–2.0 mg L−1 and 0.0021 mg L−1, respectively. The proposed method was applied to the determination of amaranth in different beverages, and the results were in good agreement with those by high-performance liquid chromatography (HPLC). The recoveries of amaranth in different beverages were between 97.93 and 105.91%. The floating adsorbent can be used as a conventional sample preparation method for the detection of low concentration analytes in complex samples.