In situ preparation of core–shell magnetic porous aromatic framework nanoparticles for mixed–mode solid–phase extraction of trace multitarget analytes

Carbon and metal based magnetic porous materials - Role in drug removal: A Comprehensive review

Development of effective adsorbents for the removal of contaminants from wastewater is indispensable due to increasing water scarcity and a lack of pure drinking water, which are prevailing as a result of rapid industrialization and population growth. Recently, the development of new adsorbents and their effective use without generating secondary waste is receiving huge consideration. In order to protect the environment from primary and secondary pollution, the development of adsorbents from wastes and their recycling have become conventional practices aimed at waste management. As a result, significant progress has been made in the synthesis of new porous carbon and metal-organic frameworks as adsorbents, with the objective of using them for the removal of pollutants. While many different kinds of pollutants are produced in the environment, drug pollutants are the most vicious because of their tendency to undergo significant structural changes, producing metabolites and residues with entirely different properties compared to their parent compounds. Chemical reactions involving oxidation, hydrolysis, and photolysis transform drugs. The resulting compounds can have detrimental effects on living beings that are present in soil and water. This review stresses the development of adsorbents with adjustable porosities for the broad removal of primary drug pollutants and their metabolites, which are formed as a result of drug transformations in environmental matrices. This keeps adsorbents from building up in the environment and prevents them from becoming significant pollutants in the future. Additionally, it stops secondary pollution caused by the deterioration of the used adsorbents. Focus on the development of effective adsorbents with flexible porosities allows for the complete removal of coexisting contaminants and makes a substantial contribution to wastewater management. In order to concentrate more on the development of flexible pore adsorbents, it is crucial to comprehend the milestones reached in the research and applications of porous magnetic adsorbents based on metal and carbon, which are discussed here.

Preparation of a β-cyclodextrin grafted magnetic biochar for efficient extraction of four antiepileptic drugs in plasma samples

Simultaneous monitoring of plasma concentration levels of multiple antiepileptic drugs (AEDs) is essential for dose adjustment in comprehensive epilepsy treatment, necessitating a sensitive technique for accurate extraction and determination of AEDs. Herein, a magnetic solid-phase extraction (MSPE) technique on the basis of modified biochar (BC) is investigated to extract four AEDs from plasma, in conjunction with high performance liquid chromatography. BC derived from Zizyphus jujuba seed shells was activated by phosphoric acid (PBC) and magnetized via coprecipitation to produce MPBC. The MPBCCD obtained after modification with β-cyclodextrin (CD) was characterized and evaluated for adsorption. It exhibited fast adsorption kinetics based on second-order kinetics and satisfactory adsorption capacity for AEDs. Then it was employed as the MSPE adsorbent and the influencing parameters were optimized. The enrichment factor was 18.75. The validation analysis revealed a favorable linearity that ranged from 0.04 to 20 μg·mL-1 along with a low limit of detection of 6.85 to 10.19 ng·mL-1. The recovery of the AEDs ranged from 78.7 to 109.2 %, with relative standard deviations below 6.7 %. Using quantum chemistry theory calculations and experimental results analysis, the adsorption mechanism was investigated. It disclosed that the suggested strategy built upon MPBCCD was appropriate for the assessment of AEDs in plasma and expanded the usage of BC as the environmentally favorable matrix for the analysis of biological samples.

The application progress of magnetic solid-phase extraction for heavy metal analysis in food: a mini review

The emerging sample pretreatment technique of magnetic solid-phase extraction (MSPE) has drawn the attention of researchers owing to its advantages of less reagent consumption, fast separation/enrichment process, high adsorption capacity, and simple operation. This paper presents a review of synthesis techniques, classification, and analysis procedures for MSPE in the detection of heavy metals in food. Magnetic adsorbents derived from silica, metal oxides, carbon, polymers, etc., are applied for the detection of heavy metals in food. Then, the recent development of the technology of MSPE for the analysis of heavy metal extraction in food is summarized in detail. Finally, the future outlook for the improvement of MSPE is also discussed.

Advanced porous organic materials for sample preparation in pharmaceutical analysis

The development of novel sample preparation media plays a crucial role in pharmaceutical analysis. To facilitate the extraction and enrichment of pharmaceutical molecules in complex samples, various functionalized materials have been developed and prepared as adsorbents. Recently, some functionalized porous organic materials have become adsorbents for pharmaceutical analysis due to their unique properties of adsorption and recognition. These advanced porous organic materials, combined with consequent analytical techniques, have been successfully used for pharmaceutical analysis in complex samples such as environmental and biological samples. This review encapsulates the progress of advanced porous materials for pharmaceutical analysis including pesticides, antibiotics, chiral drugs, and other compounds in the past decade. In addition, we also address the limitations and future trends of these porous organic materials in pharmaceutical analysis.

Preparation and evaluation of a chitosan modified biochar as an efficient adsorbent for pipette tip-solid phase extraction of triazine herbicides from rice

The low allowable limit of triazine herbicides (THs) in rice makes it imperative to develop novel sample pretreatment methods for extraction and preconcentration of THs. Herein, a phosphoric acid activated biochar (PBC) was prepared and modified by chitosan (CS). For THs with different polarities, CS-PBC with multiple interaction sites exhibited satisfactory chemisorption. On this basis, a CS-PBC-based pipette tip-solid phase extraction (PT-SPE) was developed combined with HPLC to extract THs from rice. Low limits of detection (1.41-3.35 ng g^-1), satisfactory linearity (0.01-2.00 μg g^-1, R² > 0.9974) and recoveries (96.13-116.25 %) were obtained with acceptable inter-day and intra-day precision (RSD ≤ 13.60 %). CS-PBC showed superior performance to three commercial single-mode adsorbents and comparable results to a hydrophilic-lipophilic balance adsorbent. The study explored the feasibility of PT-SPE for extracting THs from rice and broadened the application of plant biochar as an environmentally-friendly matrix in food sample pretreatment.

Magnetic Adsorbents for Wastewater Treatment: Advancements in Their Synthesis Methods

The remediation of water streams, polluted by various substances, is important for realizing a sustainable future. Magnetic adsorbents are promising materials for wastewater treatment. Although numerous techniques have been developed for the preparation of magnetic adsorbents, with effective adsorption performance, reviews that focus on the synthesis methods of magnetic adsorbents for wastewater treatment and their material structures have not been reported. In this review, advancements in the synthesis methods of magnetic adsorbents for the removal of substances from water streams has been comprehensively summarized and discussed. Generally, the synthesis methods are categorized into five groups, as follows: direct use of magnetic particles as adsorbents, attachment of pre-prepared adsorbents and pre-prepared magnetic particles, synthesis of magnetic particles on pre-prepared adsorbents, synthesis of adsorbents on preprepared magnetic particles, and co-synthesis of adsorbents and magnetic particles. The main improvements in the advanced methods involved making the conventional synthesis a less energy intensive, more efficient, and simpler process, while maintaining or increasing the adsorption performance. The key challenges, such as the enhancement of the adsorption performance of materials and the design of sophisticated material structures, are discussed as well.

Design, Preparation, and Application of Magnetic Nanoparticles for Food Safety Analysis: A Review of Recent Advances

This review (with 126 references) aims at providing an updated overview of the recent developments and innovations of the preparation and application of magnetic nanoparticles for food safety analysis. During the past two decades, various magnetic nanoparticles with different sizes, shapes, and surface modifications have been designed, synthesized, and characterized with the prospering development of material science. Analytical scientists and food scientists are among the ones who bring these novel materials from laboratories to commercial applications. Powerful and versatile surface functional groups and high surface to mass ratios make these magnetic nanoparticles useful tools for high-efficiency capture and preconcentration of certain molecules, even when they exist in trace levels or complicated food matrices. This is why more and more methods for sensitive detection and quantification of hazards in foods are developed based on these magic magnetic tools. In this review, the principles and superiorities of using magnetic nanoparticles for food pollutant analysis are first introduced, like the mechanism of magnetic solid phase extraction, a most commonly used method for food safety-related sample pretreatment. Their design and preparation are presented afterward, alongside the mechanisms underlying their application for different analytical purposes. After that, recently developed magnetic nanoparticle-based methods for dealing with food pollutants such as organic pollutants, heavy metals, and pathogens in different food matrices are summarized in detail. In the end, some humble outlooks on future directions for work in this field are provided.

Adsorptive remediation of environmental pollutants using magnetic hybrid materials as platform adsorbents

Effective separation and remediation of environmentally hazardous pollutants are burning areas of research because of a constant increase in environmental pollution problems. An extensive number of emerging contaminants in the environmental matrices result in serious health consequences in animals, humans, and plants, even at trace levels. Therefore, it is of paramount significance to quantify these undesirable pollutants, even at a very low concentration, from the natural environment. Magnetic solid-phase extraction (MSPE) has recently achieved huge attention because of its strong magnetic domain and easy separation through an external magnetic field compared with simple solid-phase extraction. Therefore, MSPE appeared the most promising technique for removing and pre-concentration of emerging pollutants at trace level. Compared to the normal solid-phase extraction, MSPE as magnetic hybrid adsorbents offers the unique advantages of distinct nanomaterials and magnetic hybrid materials. It can exhibit efficient dispersion and rapid recycling when applying to a very complex matrix. This review highlights the possible environmental applications of magnetic hybrid nanoscale materials as effective MSPE sorbents to remediate a diverse range of environmentally toxic pollutants. We believe this study tends to evoke a variety of research thrust that may lead to novel remediation approaches in the forthcoming years.

Construction of hydroxyl functionalized magnetic porous organic framework for the effective detection of organic micropollutants in water, drink and cucumber samples

Organic micropollutants have been extensively detected in environmental waters, posing severe hazards to organisms and humans. Effective detection of micropollutants in environmental water and food samples is of significant importance. Herein, a novel magnetic porous organic framework (labeled as M-Qu-POF) was synthesized using natural quercetin as building units via a facile azo-coupling reaction for the first time. Featuring with good magnetism, intrinsic porosity, high surface area and hydrophilic-lipophilic (amphiphilic) structure, the M-Qu-POF displayed high adsorption capacity for phenylurea herbicides (PUHs) pollutants. The adsorption mechanism was investigated by theory calculation, confirming that the hydrogen bonds interaction, π-π interactions and electrostatic interactions play an important role in the adsorption. With the M-Qu-POF as adsorbent, a magnetic solid phase extraction-high performance liquid chromatography method was first established for simultaneous enrichment and detection of six PUHs in environmental water, tea drink and cucumber samples. Under the optimized experimental conditions, good linear range, low detection limits and high enrichment factors were obtained. The method was successfully applied for determination of PUHs in environmental water, tea drink and cucumber samples with satisfactory recoveries (80.0-118%). The result demonstrates that the M-Qu-POF material has a good application prospect in the detection of other organic micropollutants.

Amino-based magneto-polymeric-modified mixed iron hydroxides for magnetic solid phase extraction of phenol residues in environmental samples

Mixed iron hydroxides (MIHs) modified with different amino-based polymeric materials, including aminopropyltriethoxysilane, polydopamine, diaminobenzoic acid, polyaniline, and polyphenylenediamine, were comparatively investigated as sorbents for the extraction of phenol compounds. Polyphenylenediamine-modified mixed iron hydroxides (MIH@PPDA) showed high adsorption capability for most target analytes. Its ferromagnetic behavior, with a magnetization of 17.38 emu g^-1, was sufficient for subsequent use in magnetic solid-phase extraction (MSPE). The functional groups, morphology, and magnetic properties of this magnetic nanomaterial were investigated using Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, X-ray diffraction, and CHN analysis. High-performance liquid chromatography with a photodiode array detector was used to quantify phenol compounds. The experimental parameters affecting the efficiency of the entire MSPE process were optimized. Good linearity in the range of 0.5-1000 µg L^-1 was obtained (depended on the compound). The detection and quantitation limits varied from 0.01 to 0.3 µg L^-1 and 0.03 to 0.9 µg L^-1, respectively. The enrichment factors for all phenol compounds were in the range of 80-285. The precision in terms of intra- and inter-day relative standard deviations were below 5.8% and 6.2%, respectively. The developed MSPE method was applied to analyze phenol compounds in diverse samples, including soil, drinking water, and fruit. Relative recoveries of 76.7-130.1% were obtained. The MIH@PPDA magneto-polymeric sorbent exhibits good stability and is reliable for a variety of phenol compounds.

The fabrication of a covalent triazine-based organic framework for the solid-phase extraction of fourteen kinds of sulfonamides from meat samples

A novel covalent triazine-based organic framework (CTF), SCAU-2, was fabricated and used as an adsorbent for the solid-phase extraction of fourteen kinds of sulfonamides (SAs) from meat. Another CTF, SCAU-1, was adopted as a comparison material, as it has a similar motif. A series of structural characterization steps was carried out on the synthesized materials and several parameters were investigated during the extraction process, including the amount of adsorbent, the dilution ratio, the pH of the sample, and the washing and elution solvents. After detection with UHPLC-Q/TOF-MS/MS, the results revealed that SCAU-2 showed high extraction efficiencies towards the selected SAs. The LOD values are from 0.05 to 0.54 ng g-1, and the recoveries are from 84.1% to 91.9%, with RSDs ranging from 3.2% to 4.8% for SCAU-2 when spiked at 50 ng g-1. The results demonstrated that the proposed method has good applicability for the determination of SAs in complicated samples.

Preparation of multitarget immunomagnetic beads based on metal-organic frameworks and their application in food samples

A new type of immunomagnetic bead based on the metal-organic framework materials (MOFs) and the magnetic core (Fe₃O₄) was prepared for analysis of the mycotoxins in food samples. The MOF conjugated with the monoclonal antibodies (McAbs) was coated on the surface of Fe₃O₄ beads by reversed-phase microemulsion method, which could purify deoxynivalenol (DON), zearalenone (ZEN), T-2, and HT-2 mycotoxins at the same time. The composite (Fe₃O₄@AMP&ZnCl₂@McAbs) was characterized by Transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), and Energy dispersive spectroscopy (EDS) mapping. The results showed that the synthesis of the composite was successful. The maximum toxin adsorption capacity per 100 mg of composite was DON 688.26 ng, ZEN 864.98 ng, and T-2/HT-2 2801.80 ng, and in adding recovery experiment, the recovery of four mycotoxins decreased slightly with the increase of usage times, but still maintained a high adsorption rate and stability. For effectiveness comparison and evaluation, the composite and commercial DZTMS-PREP immune affinity column were used to treat three samples of corn, wheat, and oat flour, and the purification effect of the two pretreatment methods on the four toxins was similar.

Monodisperse pillar[5]arene-based polymeric sub-microsphere for on-line extraction coupling with high-performance liquid chromatography to determine antioxidants in the migration of food contact materials

The monodisperse pillar[5]arene-based polymeric sub-microsphere was prepared by polycondensation of hydroxylated pillar[5]arene and cyanuric chloride through a one-pot reaction in mild condition. The preparation was realized by a simple two-step temperature-programmed process without heating operation. The obtained polymeric sub-microsphere exhibited monodisperse and regular spherical structure with uniform particle size distribution of 220-320 nm accounting for 94%. The prominent adsorption capacity of the polymeric sub-microsphere for antioxidants was demonstrated and attributed to the synergistic effect of the cladding interaction with the π-electron rich cavity and hydrophilic interaction with terminal hydroxyl on pillar[5]arene. Then the pillar[5]arene sub-microsphere was packed into a micro-column to realize effective on-line enrichment of antioxidants coupling with high-performance liquid chromatography (HPLC). The flow rate of extraction and desorption solvent, clean-up and desorption volume were assessed to optimize the method. The method showed wide linear ranges with R² greater than 0.9926, low limits of detection (0.030-0.20 μg/L) and limits of quantification (0.10-0.67 μg/L). The developed method was successfully applied to determine trace antioxidants in the migration of food contact materials with simulated solution, which demonstrated the promising potential of this method for practical analysis. Furthermore, the migration behavior of antioxidants from food packaging materials into different food matrix was also investigated.

Preparation of Magnetic Porous Aromatic Framework for Rapid and Efficient Removal of Organic Pollutants from Water

In this study, efforts were made to prepare a porous aromatic framework (PAF) with build-in magnetic nanoparticles (Fe₃O₄-PAF) for use as an efficient adsorbent for the removal of organic pollutants from water. The Fe₃O₄-PAF showed good handleability and could be recovered easily by magnetic separation. As a proof of concept, the adsorption properties of Fe₃O₄-PAF were investigated to remove 2,4-dichlorophenol (2,4-DCP) and bisphenol A (BPA) from water. The Fe₃O₄-PAF showed a fast adsorption rate, high adsorption efficiency and high adsorption capacities. It adsorbed 2,4-DCP (0.1 mmol L^-1) and BPA (0.1 mmol L^-1) with pseudo-second-order rate constant (k₂) of 2.1 and 3.54 g mg^-1 min^-1, respectively. According to the Langmuir isotherm model, the maximum adsorption capacities of 2,4-DCP and BPA onto Fe₃O₄-PAF were calculated to be 234.74 and 233.65 mg g^-1, respectively. The Fe₃O₄-PAF also featured good tolerance to harsh conditions, facilitating its application in a real water environment. It could be regenerated easily and reused multiple times without obvious loss of efficiency. In summary, this study provides a general and effective way to improve the handleability of PAFs and expands the practical application of PAF-based materials.

Controlled Fabrication of Silica@Covalent Triazine Polymer Core-Shell Spheres as a Reversed-Phase/Hydrophilic Interaction Mixed-Mode Chromatographic Stationary Phase

The unique properties of covalent triazine-based organic framework/polymers, including large surface area, hydrophilic-lipophilic-balanced adsorption, and economical preparation, make it a promising candidate as a stationary phase for high-performance liquid chromatography. However, irregular shapes and wide size distributions of such particles hinder column packing, resulting in a low column efficiency or a high back pressure. Herein, we describe the fabrication of SiO₂@ covalent triazine-based organic polymer (CTP) core-shell microspheres with a distinct sphere-coating-sphere appearance using aminosilica as the supporting substrate to grow the CTP shell. By adjusting the amount of reactants, the thickness of the CTP shell, which consists of triazine and 1,3,5-triphenylbenzene monomers, was easily controlled. The developed core-shell microspheres were characterized via scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, solid-state ¹³C nuclear magnetic resonance analysis, and N₂ adsorption experiments. The synergism of the triazine and aromatic moieties on CTP provides the new stationary phase with multiple retention mechanisms, including hydrophobic, π-π, electron donor-acceptor, hydrogen-bonding interactions, and so forth. On the basis of these interactions, successful separation and higher shape selectivity were achieved among several analytes that vary in polarity under both reversed-phase and hydrophilic interaction liquid chromatography conditions. Therefore, SiO₂@CTP microspheres combine the advantages of good column packing properties of the uniform monodisperse silica microspheres and the recognition performance of CTP, generating flexible selectivity and application prospect for both hydrophilic and hydrophobic analytes.

Fabrication of glucose-derived carbon-decorated magnetic microspheres for extraction of bisphenols from water and tea drinks

Glucose-derived carbon-decorated magnetic microspheres were synthesized by an easy hydrothermal carbonization method and used as a high-efficiency adsorbent to extract bisphenols in water and tea drinks. The as-prepared carbon-decorated magnetic microspheres had a well-defined core-shell structure with a shell thickness of about 5 nm. The microspheres possessed high saturation magnetization at 60.8 emu/g and excellent chemical stability in aqueous solution. The experimental parameters affecting the extraction efficiency, including extraction time, pH, adsorbent dosage, desorption solvents, desorption time, and solution volume were evaluated. Electrostatic and π-π interactions were the major driving forces during extraction. Overall, a new magnetic solid-phase extraction method of determining bisphenols was developed on the basis of as-prepared magnetic microspheres. The method had a wide linear range, low limits of detection (0.03-0.10 µg/L), and high recoveries (85.4-104.6%).

Preparation of porous aromatic framework modified graphene oxide for pipette-tip solid-phase extraction of theophylline in tea

A new material called as porous aromatic frameworks modified graphene oxide (PAFs-GO) was synthesized, and it was used as an adsorbent in pipette-tip SPE for the effective purification and enrichment of theophylline in tea sample by HPLC. The properties of PAFs-GO were characterized by field emission SEM, FTIR, thermogravimetry analysis and Brunauer Emmett Teller N₂ adsorption-desorption analysis. The results of static adsorption and dynamic adsorption test showed PAFs-GO had higher adsorption ability (93.25 mg/g) than graphene oxide. The LOD and LOQ of the method were 0.0141 and 0.0471 µg/mL, respectively. The acceptable method reproducibility was found as intra- and inter-day precisions, yielding the RSDs <4.62%. By introducing PAFs as support skeleton, the specific surface area of GO was effectively increased, and the penetrability was improved. Studies showed that the proposed method had been successfully applied for purification and enrichment of theophylline in complex tea matrix.

A porous aromatic framework as a versatile fiber coating for solid-phase microextraction of polar and nonpolar aromatic organic compounds

A porous aromatic framework (PAF) derived from triphenylamine (type PAF-41) was prepared and is shown to be a viable coating for fibrous solid-phase microextraction (SPME). PAF-41 can be easily synthesized and has a high surface area, a rich π-electron structure, and electron-rich nitrogen atoms in its framework. The PAF-41-coated fibrous SPME extractor was combined with a gas chromatographic separation and flame ionization detection. The method was applied to the quantitation of some aromatic organic compounds (AOCs), including polar amphetamine and methamphetamine and nonpolar ethylbenzene, o-, m- and p-xylenes, and styrene. The method was optimized after which a linear response is found for the 10-500 ng·mL^-1 amphetamine and methamphetamine concentration ranges. The limits of detection are 1.0 and 0.5 ng·mL^-1; and relative standard deviations for six repeated extractions with a single fiber are 5.3 and 6.7%. The method was applied for the determination of amphetamine and methamphetamine in spiked urine samples without any pretreatment except for dilution with water. The PAF-41 modified fiber also was applied to the extraction of styrene, xylenes and ethylbenzene. The enrichment capacities of the extractor for these AOCs were superior to those of commercial SPME extractors. Graphical abstract (a) Schemetic of the PAF-41-coated solid-phase microextraction (SPME) fiber. (b) Scanning electron microscope images of the PAF-41 fiber.

Simultaneous determination of three sulfanilamide artificial sweeteners in foodstuffs by capillary electrophoresis coupled with contactless conductivity detection based on porous aromatic frameworks enhanced solid phase extraction

In this paper, a simple and easy method of solid phase extraction (SPE) followed by capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C4D) is evaluated as a novel approach for the simultaneous determination of acesulfame-K (ACE), sodium saccharin (SAC), and sodium cyclamate (CYC) in foodstuffs without derivatization. To reduce the complex matrix interference resulting from the constituents of samples and enriched targets, porous aromatic frameworks (PAFs) enhanced SPE, a suitable sample pretreatment procedure, was introduced. Several factors affecting extraction efficiency and electrophoretic separation were investigated. Additionally, the interaction mechanisms between the host (PAF-6) and guests (ACE, SAC, and CYC) were studied. Under the optimum conditions, three sulfanilamide artificial sweeteners were baseline separated within 8 min, exhibiting a linear calibration over two orders of magnitude (R2 > 0.995). The limits of detection (LOD) and quantification (LOQ) were considered better than those usually obtained by CE with ultraviolet and C4D detection. The proposed SPE–CE–C4D method has been successfully applied to analyse beverage samples and candied fruits with recoveries in the range of 78.89%–92.00%.

Facile Preparation of Dual-Shell Novel Covalent-Organic Framework Functionalized Magnetic Nanospheres Used for the Simultaneous Determination of Fourteen Trace Heterocyclic Aromatic Amines in Nonsmokers and Smokers of Cigarettes with Different Tar Yields Based on UPLC-MS/MS

The facile preparation, characterization, and application of novel dual-shell TpBD (a kind of covalent-organic framework) coated magnetic nanospheres as sorbents for simple, fast, and high selectivity capture of 14 heterocyclic aromatic amines (HAAs) are reported. Quantum chemistry theory calculations were conducted to directly and quantifiably describe the multiple interactions, including π-π, hydrogen bonding, cation-π, static electricity, and ion-exchange, between TpBD and heterocyclic aromatic amines. The excellent adsorption capacity of TpBD coated magnetic nanospheres was further evaluated by extraction of 14 HAAs from nonsmokers' and smokers' urine samples. Under the optimized conditions, the magnetic solid phase extraction process can be completed with high recovery ranging from 95.4% to 129.3%. After being washed with acetonitrile and water successively, the collected sorbents can be easily recycled and reused five times without any significant difference in performance. Coupled with the ultra performance liquid chromatography-tandem mass spectrometer detection, the exposure level of HAAs in nonsmokers and smokers smoking cigarettes with different tar yields were successfully explored. And, this implied that the robust method based on the versatile TpBD coated dual-shell magnetic nanospheres sorbents represents a great potential application in the analysis of disease markers and body fluids.

Determination of Six Macrolide Antibiotics in Chicken Sample by Liquid Chromatography-Tandem Mass Spectrometry Based on Solid Phase Extraction

In this paper, a simple and effective method for the determination of six macrolide antibiotics (MACs), including tylosin, tilmicosin, azithromycin, clarithromycin, roxithromycin, and kitasamycin, in the chicken sample using liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed based on a self-built porous aromatic framework- (PAF-) based solid phase sorbent. The main parameters influencing the extraction efficiency, such as sorbent amounts, type of the eluent, pH of the sample, and the eluent volume, were evaluated. Under the optimized condition, the limits of detection were from 0.2 to 0.5 μg·kg^-1. The recoveries of the method ranged from 82.1% to 101.4% with the relative standard deviations less than 11.1%. All the results demonstrated that the established method is potential for the determination of macrolide antibiotics in food safety analysis and monitoring.

Facile preparation of a cationic COF functionalized magnetic nanoparticle and its use for the determination of nine hydroxylated polycyclic aromatic hydrocarbons in smokers’ urine

A novel cationic-COF coated double-shell magnetic sorbent, possessing excellent dispersive capability, high stability, and desirable absorption affinity, was prepared.

Recent advances in mixed-mode chromatographic stationary phases

Mixed-mode phases have become very popular in the last decade, and the number of new mixed/multi-mode sorbents is growing fast. Unlike single-mode stationary phases, perfectly suited for the separation of the analytes possessing similar physicochemical properties, for instance reversed-phase chromatography for hydrophobic solutes, mixed-mode sorbents providing multimodal interactions can render better separation selectivity for complex mixtures of solutes differing significantly in their physicochemical characteristics. The most frequent modern mixed-mode stationary phases are di/tri-mode sorbents embracing the following interactions, hydrophobic, electrostatic (coulombic), and hydrophilic. According to their structures, it is possible to distinguish silica-based, polymer-based, hybrid, and monolithic mixed-mode stationary phases. Herewith, newly synthesized mixed-mode sorbents developed within the last two and half years are categorized, discussed, and summarized. The main attention is devoted to the description of the synthetic routes and characterization methods applied for the new stationary phases.

Porous Organic Frameworks: Advanced Materials in Analytical Chemistry

Porous organic frameworks (POFs), a general term for covalent-organic frameworks (COFs), covalent triazine frameworks (CTFs), porous aromatic frameworks (PAFs), etc., are constructed from organic building monomers with strong covalent bonds and have generated great interest among researchers. The remarkable features, such as large surface areas, permanent porosity, high thermal and chemical stability, and convenient functionalization, promote the great potential of POFs in diverse applications. A critical overview of the important development in the design and synthesis of COFs, CTFs, and PAFs is provided and their state-of-the-art applications in analytical chemistry are discussed. POFs and their functional composites have been explored as advanced materials in "turn-off" or "turn-on" fluorescence detection and novel stationary phases for chromatographic separation, as well as a promising adsorbent for sample preparation methods. In addition, the prospects for the synthesis and utilization of POFs in analytical chemistry are also presented. These prospects can offer an outlook and reference for further study of the applications of POFs.

Applications of Metal-Organic Frameworks in Food Sample Preparation

Food samples such as milk, beverages, meat and chicken products, fish, etc. are complex and demanding matrices. Various novel materials such as molecular imprinted polymers (MIPs), carbon-based nanomaterials carbon nanotubes, graphene oxide and metal-organic frameworks (MOFs) have been recently introduced in sample preparation to improve clean up as well as to achieve better recoveries, all complying with green analytical chemistry demands. Metal-organic frameworks are hybrid organic inorganic materials, which have been used for gas storage, separation, catalysis and drug delivery. The last few years MOFs have been used for sample preparation of pharmaceutical, environmental samples and food matrices. Due to their high surface area MOFs can be used as adsorbents for the development of sample preparation techniques of food matrices prior to their analysis with chromatographic and spectrometric techniques with great performance characteristics.