High-Throughput and High-Efficient Micro-solid Phase Extraction Based on Sulfonated-Polyaniline/Polyacrylonitrile Nanofiber Mats for Determination of Fluoroquinolones in Animal-Origin Foods

Recent advances and applications of ionic covalent organic frameworks in food analysis

Ionic covalent organic frameworks with both crystallinity and charged sites have attracted significant attention from the scientific community. The versatile textural structures, precisely defined channels, and abundant charged sites of ionic COFs offer immense potential in various areas such as separation, sample pretreatment, ion conduction mechanisms, sensing applications, catalytic reactions, and energy storage systems. This review presents a comprehensive overview of facile preparation methods for ionic covalent organic frameworks (iCOFs), along with their applications in food sample pretreatment techniques such as solid-phase extraction (SPE), magnetic solid-phase extraction (MSPE), and dispersive solid-phase extraction (DSPE). Furthermore, it highlights the extensive utilization of iCOFs in detecting various food contaminants including pesticides, contaminants from food packaging, veterinary drugs, perfluoroalkyl substances, and poly-fluoroalkyl substances. Specifically, this review critically discusses the limitations, challenges, and future prospects associated with employing iCOF materials to ensure food safety.

Effective extraction and determination of 24 quinolones in water and egg samples using a novel magnetic covalent organic framework combined with UPLC-MS/MS

The excessive use of quinolones (QNs) has seriously threatened human health. In this study, a novel functionalized magnetic covalent organic framework Fe3O4@SiO2@Ah-COF was fabricated with biphenyl-3,3',5,5'-tetracarbaldehyde and hydrazine hydrate (85%) as monomers and was used as a magnetic solid-phase extraction (MSPE) absorbent for the determination of 24 QNs in water and egg samples through ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The extraction parameters of MSPE were optimized, including pH, adsorbent dosage, adsorption time, and eluent type. An effective and rapid detection method was then established, which showed good linearity (R2 ≥ 0.9990), low limits of detection (0.003-0.036 μg L-1) and low limits of quantitation (0.008-0.110 μg L-1) for QNs. The good recoveries of 24 QNs in water and egg samples were in the range of 70.3-106.1% and 70.4-119.7%, respectively, with relative standard deviations lower than 10% (n = 5). As a result, Fe3O4@SiO2@Ah-COF is a promising magnetic adsorbent, and the established method was successfully applied for the determination of 24 QNs in water and egg samples.

Comparison of ZrO2 Particles and Polyaniline as Additives in Polystyrene-Based Sorbents for the Micro-Solid Phase Extraction of Psychoactive Drugs from Biofluids

The intensive development of extraction methods based on μ-SPE extraction contributes to the increased interest in the synthesis of new sorption materials. This work presents the characterization of polystyrene fibers and polystyrene fibers blended with ZrO2 particles or polyaniline obtained by electrospinning and their use in the extraction of selected psychoactive drugs from biological samples. The characteristic of produced fibers is made by performing SEM images, measuring average fiber diameter, and examining their sorption abilities. Among the fibers based on pure polystyrene, tested in the first stage, the best sorption properties are demonstrated for the fibers obtained from a polystyrene solution in DMF with a concentration of 17.5 wt%. In the next stage, this material was modified with synthesized ZrO2 particles and polyaniline. Among the tested materials, the sorbent based on polystyrene with polyaniline shows the best sorption properties of the tested substances. The use of this material in the μ-SPE in a needle enables the extraction of selected compounds from aqueous and biological samples such as urine and human plasma.

Simple, fast and eco-friendly micro-solid phase extraction based on thiol and ionic liquid bi-functional nanofibers membrane for the determination of sulfonamides in environmental water

BACKGROUND

Sulfonamides (SAs) are a class of synthetic antibacterial agents that are diffusely used in the medical industry and animal husbandry. Their prevalence in the influents and effluents of water treatment plants, as well as in rivers and groundwater, has provoked worldwide concern. Monitoring SAs in environmental water is of great significance for public health. However, most of the available detection techniques for SAs are cumbersome and time-consuming. With the increasing number of actual samples, simple, fast and environmentally friendly analytical methods are always in demand.

RESULTS

Herein, we describe a highly efficient micro-solid phase extraction (μ-SPE) sample preparation technique based on a novel thiol and ionic liquid bi-functional nanofibers membrane (IL-SH-PAN NFsM) for multi-residue detection of sulfonamides (SAs) in water samples. By the synergistic effect of -SH and -IL, the as-prepared IL-SH-PAN NFsM demonstrated high adsorption capacity and excellent selectivity for SAs. The water samples can be directly used for μ-SPE without pH and ionic strength adjustment, and the eluent can be directly collected for HPLC-MS/MS analysis. Compared with other methods reported in the literature, this method required much shorter extraction time (2 min for a batch), much less amount of adsorbent (4.0 mg) and organic solvent (0.5 mL), while providing much higher sensitivity (1.4-3.9 ng L-1), and fine recoveries (88.8%-117.7%) with relative standard deviations less than 4.26%.

SIGNIFICANCE AND NOVELTY

A bi-functional nanofibers membrane was prepared for efficient extraction of SAs. The adsorbent exhibited superior adsorption performance and excellent selectivity. The underlying interaction mechanisms derived from -SH and -IL were proposed, which provide a new idea for preparing versatile adsorbents. Rapid, efficient and sensitive detection of SAs in water was achieved. The novel sample preparation technique can be expected as an efficient method for routine trace SAs residue monitoring in various water samples.

Current analytical strategies for the determination of quinolone residues in milk

Quinolones are potent antibacterial drugs extensively utilized for treating bacterial infections in poultry. However, the presence of quinolone antibiotic residues in milk is a matter of concern due to potential health risks and adverse effects on milk quality. This review provides an overview of current analytical strategies for the determination of quinolone residues in milk. Various sample preparation techniques, such as liquid-phase extraction, solid-phase extraction and QuEChERS, are discussed, along with detection methods including instrument-based detection, immune-based detection, and microbial detection. The advantages and limitations of each method are highlighted, as well as their applicability in different stages of milk production. Additionally, recent advancements in sample preparation and detection methods are presented. This comprehensive review aims to contribute to the development of accurate and reliable methods for the detection of quinolone residues in milk, ensuring the safety and quality of dairy products.

Development of a Screening Method for Fluoroquinolones in Meat Samples Using Molecularly Imprinted Carbon Dots

An accurate and simple screening method has been developed for the determination of fluoroquinolone antibiotics. Carbon dots were synthesized by simple hydrothermal treatment as highly fluorescent nano-sensors. They were subsequently used in the synthesis of organic-based molecularly imprinted polymers to develop fluorescence-based polymeric composites using enoxacin as a representative dummy template molecule of fluoroquinolones. The method was optimized concerning the pH of the medium and composite concentration. The normalized fluorescence intensity showed efficient quenching under optimized conditions upon successive addition of the template, with an excellent correlation coefficient. The proposed method was applied to eight other fluoroquinolones, exhibiting, in all cases, good correlation coefficients (0.65-0.992) within the same linearity range (0.03-2.60 mg mL-1). Excellent detection and quantification limits were been obtained for the target analytes down to 0.062 and 0.186 mg L-1, respectively. All studied analytes showed no interference with enrofloxacin, the most commonly used veterinary fluoroquinolone, with a percentage of cross-reactivity varying from 89.00 to 540.00%. This method was applied successfully for the determination of enrofloxacin in three different types of meat samples: beef, pork, and chicken, with good recoveries varying from 70 to 100% at three levels. This new procedure is an easy analytical method that can be useful as a screening method for monitoring the environmental hazard of fluoroquinolones in quality control laboratories.

Preparation of COPs Mixed Matrix Membrane for Sensitive Determination of Six Sulfonamides in Human Urine

In this study, TpDMB-COPs, a specific class of covalent organic polymers (COPs), was synthesized using Schiff-base chemistry and incorporated into a polyvinylidene fluoride (PVDF) polymer for the first time to prepare COPs mixed matrix membranes (TpDMB-COPs-MMM). A membrane solid-phase extraction (ME) method based on the TpDMB-COPs-MMM was developed to extract trace levels of six sulfonamides from human urine identified by high-performance liquid chromatography (HPLC). The key factors affecting the extraction efficiency were investigated. Under the optimum conditions, the proposed method demonstrated an excellent linear relationship in the range of 3.5-25 ng/mL (r2 ≥ 0.9991), with the low limits of detection (LOD) between 1.25 ng/mL and 2.50 ng/mL and the limit of quantification (LOQ) between 3.50 ng/mL and 7.00 ng/mL. Intra-day and inter-day accuracies were below 5.0%. The method's accuracy was assessed by recovery experiments using human urine spiked at three levels (7-14 ng/mL, 10-15 ng/mL, and 16-20 ng/mL). The recoveries ranged from 87.4 to 112.2% with relative standard deviations (RSD) ≤ 8.7%, confirming the applicability of the proposed method. The developed ME method based on TpDMB-COPs-MMM offered advantages, including simple operation, superior extraction affinity, excellent recycling performance, and easy removal and separation from the solution. The prepared TpDMB-COPs-MMM was demonstrated to be a promising adsorbent for ME in the pre-concentration of trace organic compounds from complex matrices, expanding the application of COPs and providing references for other porous materials in sample pre-treatment.

One Stone Two Birds: An Upconversion Nanosensor for Sensitive Detection of Fluoroquinolones in Aquatic Products Based on Chelation Recognition

Excessive residues of fluoroquinolones (FQs) in aquatic products have become a growing issue in recent years. Herein, we demonstrate an upconversion fluorescence nanosensor constructed by a one-stone-two-birds strategy, where Fe3+ not only quenches upconversion fluorescence with high efficiency but also specifically recognizes the bidentate ligand structure of FQs. Compared to existing methods, the proposed sensor is simpler to synthesize and cheap and has more storage stability due to the unification of the quencher and recognition molecule. Enrofloxacin (ENR) was chosen as a representative veterinary drug for FQs to verify the effectiveness of the nanosensor. Under optimal conditions, the range of detection for ENR was 2.0 × 10-2 to 2.0 × 102 μg/mL, with a limit of detection of 1.08 × 10-3 μg/mL. The developed nanosensor was further validated by high-performance liquid chromatography-ultraviolet (HPLC-UV) without significant differences in practical detection. Hence, this study offers a potential strategy for the detection of FQs.

Efficient adsorptive removal of aminoglycoside antibiotics from environmental water

Aminoglycoside antibiotics (AGs) in environmental water are emerging pollutants that must be removed to protect human health and the ecosystem. However, removing AGs from environmental water remains a technical challenge due to high polarity, stronger hydrophilicity and unique characteristics of polycation. Herein, a thermal-crosslinked polyvinyl alcohol electrospun nanofiber membrane (T-PVA NFsM) is synthesized and firstly leveraged as the adsorptive removal of AGs from environmental water. The thermal crosslinking strategy is demonstrated to enhance both the water resistance and hydrophilicity of T-PVA NFsM, thereby effectively interacting with AGs with high stability. Experimental characterizations and analog calculations indicate that T-PVA NFsM utilizes multiple adsorption mechanisms, including electrostatic and hydrogen bonding interactions with AGs. As a result, the material achieves 91.09%-100% adsorption efficiencies and a maximum adsorption capacity of 110.35 mg g^-1 in less than 30 min. Furthermore, the adsorption kinetics follow the pseudo-second-order model. After eight consecutive adsorption-desorption cycles, T-PVA NFsM with a simplified recycling process maintains a sustainable adsorption capability. Compared with other forms of adsorption materials, T-PVA NFsM has significant advantages such as less consumption of adsorbent, high adsorption efficiency and fast removal speed. Therefore, T-PVA NFsM-based adsorptive removal holds promise for eliminating AGs from environmental water.

Advances in solid-phase extraction techniques: Role of nanosorbents for the enrichment of antibiotics for analytical quantification

Antibiotics are life-saving medications for treating bacterial infections; however it has been discovered that resistance developed by bacteria against these incredible agents is the primary contributing factor to rising global mortality rates. The fundamental cause of the emergence of antibiotic resistance in bacteria is the presence of antibiotic residues in various environmental matrices. Although antibiotics are present in diluted form in environmental matrices like water, consistent exposure of bacteria to these minute levels is enough for the resistance to develop. So, identifying these tiny concentrations of numerous antibiotics in various and complicated matrices will be a crucial step in controlling their disposal in those matrices. Solid phase extraction, a popular and customizable extraction technology, was developed according to the aspirations of the researchers. It is a unique alternative technique that could be implemented either alone or in combination with other approaches at different stages because of the multitude of sorbent varieties and techniques. Initially, sorbents are utilized for extraction in their natural state. The basic sorbent has been modified over time with nanoparticles and multilayer sorbents, which have indeed helped to accomplish the desired extraction efficiencies. Among the current traditional extraction techniques such as liquid-liquid extraction, protein precipitation, and salting out techniques, solid-phase extractions (SPE) with nanosorbents are most productive because, they can be automated, selective, and can be integrated with other extraction techniques. This review aims to provide a broad overview of advancements and developments in sorbents with a specific emphasis on the applications of SPE techniques used for antibiotic detection and quantification in various matrices in the last two decades.

Recent advances and applications of magnetic covalent organic frameworks in food analysis

Recently, covalent organic frameworks (COFs) have been widely used to prepare magnetic adsorbents for food analysis due to their highly tunable porosity, large specific surface area, excellent chemical and thermal stability and large delocalised π-electron system. This review summarises the main types and preparation methods of magnetic COFs and their applications in food analysis for the detection of pesticide residues, veterinary drugs, endocrine-disrupting phenols and estrogens, plasticisers and other food contaminants. Furthermore, challenges and future outlook in the development of magnetic COFs for food analysis are discussed.

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.

Simultaneous Determination of Nine Quinolones in Pure Milk Using PFSPE-HPLC-MS/MS with PS-PAN Nanofibers as a Sorbent

In this study, a packed-fiber solid-phase extraction (PFSPE)-based method was developed to simultaneously detect nine quinolones, including enrofloxacin (ENR), ciprofloxacin (CIP), ofloxacin (OFL), pefloxacin (PEF), lomefloxacin (LOM), norfloxacin (NOR), sarafloxacin (SAR), danofloxacin (DAN), and difloxacin (DIF), in pure milk, using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). Polystyrene (PS) and polyacrylonitrile (PAN) were combined to form PS-PAN composite nanofibers through electrospinning. The nanofibers were used to prepare the home-made extraction columns, and the process was optimized and validated using blank pure milk. The analytical method showed high accuracy, and the recoveries were 88.68–97.63%. Intra-day and inter-day relative standard deviations were in the ranges of 1.11–6.77% and 2.26–7.17%, respectively. In addition, the developed method showed good linearity (R² ≥ 0.995) and low method quantification limits for the nine quinolones (between 1.0–100 ng/mL) for all samples studied. The nine quinolones in the complex matrix were directly extracted using 4.0 mg of PS-PAN composite nanofibers as a sorbent and completely eluted in 100 μL elution solvent. Therefore, the developed PFSPE-HPLC-MS/MS is a sensitive and cost-effective technique that can effectively detect and control nine quinolones in dairy products.

Analysis of anticancer compound, indole-3-carbinol, in broccoli using a new ultrasound-assisted dispersive-filter extraction method based on poly(deep eutectic solvent)-graphene oxide nanocomposite

Indole-3-carbinol (I3C), an important anticancer compound found in broccoli, has attracted considerable attention. The rapid extraction and accurate analysis of I3C in the pharmaceutical industry in broccoli is challenging as I3C is unstable at low pH and high temperature. In this study, a rapid, accurate, and low-cost ultrasound-assisted dispersive-filter extraction (UADFE) technique based on poly(deep eutectic solvent)-graphene oxide (PDES-GO) adsorbent was developed for the isolation and analysis of I3C in broccoli for the first time. PDES-GO with multiple adsorption interactions and a fast mass transfer rate was synthesized to accelerate adsorption and desorption. UADFE was developed by combining dispersive solid-phase extraction (DSPE) and filter solid-phase extraction (FSPE) to realize rapid extraction and separation. Based on the above two strategies, the proposed PDES-GO-UADFE method coupled with high-performance liquid chromatography (HPLC) allowed the rapid (15-16 min), accurate (84.3%-96.4%), and low-cost (adsorbent: 3.00 mg) analysis of I3C in broccoli and was superior to solid-phase extraction, DSPE, and FSPE methods. The proposed method showed remarkable linearity (r=0.9998; range: 0.0840-48.0 μg/g), low limit of quantification (0.0840 μg/g), and high precision (relative standard deviation ≤5.6%). Therefore, the PDES-GO-UADFE-HPLC method shows significant potential in the field of pharmaceutical analysis for the separation and analysis of anti-cancer compounds in complex plant samples.

Synthesis of surface dual-template molecularly imprinted silica nanoparticles for extraction of ciprofloxacin and norfloxacin

Synthesis of selective dual-template molecularly imprinted silica nanoparticles (MI-SiNPs) on the surface of graphene quantum dots (GQDs) for the simultaneous extraction of ciprofloxacin (CIP) and norfloxacin (NOR) from biological samples.

[Determination of tetracycline and fluoroquinolone residues in fish by polydopamine nanofiber mat based solid phase extraction combined with ultra performance liquid chromatography-tandem mass spectrometry]

Tetracyclines and fluoroquinolones are common antibacterial drugs used in aquaculture, and their residues may pose a risk to human health. The low concentration of drug residues and complex matrixes such as fats and proteins in aquatic products necessitate the urgent development of efficient sample pretreatment methods. Solid phase extraction (SPE) is the most common sample pretreatment method, in which the core is an adsorbent. Compared with traditional SPE adsorbents, nanofiber mat (NFsM) has more interaction sites because of their large specific surface area. Furthermore, NFsMs modified with specific functional groups can significantly improve the extraction efficiency of tetracyclines and fluoroquinolones. Polydopamine (PDA) is spontaneously synthesized by the oxidative self-polymerization of dopamine-hydrochloride in alkaline solutions (pH>7.5). Because of its rich amino and catechol groups, PDA can form π-π stacking, electrostatic attraction, hydrophobic interaction, and hydrogen bonding interactions with target molecules. By exploiting the above advantages, polystyrene (PS) NFsM, as a template, was prepared by the electrostatic spinning method, and PDA-PS NFsM was obtained by functional modification of PDA through self-polymerization. Fourier transform infrared spectroscopy (FT-IR) and field-emission scanning electron microscopy (FESEM) were used to characterize the synthesized PS NFsM and PDA-PS NFsM. It was proved that PDA was successfully modified on the PS NFsM, with the SEM images revealing a rough outer core shell structure and an inner honeycomb structure. Subsequently, the handmade SPE column with PDA-PS NFsM was completed. A novel and efficient screening analytical method based on PDA-PS NFsM for the simultaneous determination of three tetracyclines (tetracycline (TET), chlortetracycline (CTC), and oxytetracycline (OTC)) and three fluoroquinolones (enrofloxacin (ENR), ciprofloxacin (CIP), and norfloxacin (NOR)) in fish by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established. The SPE procedure was optimized to develop an efficient method for sample preparation. Evaluate parameters including the amount of NFsM usage, ionic strength, flow rate of the sample solution, composition of eluent, and breakthrough volume were investigated. Only (20±0.1) mg of PDA-PS NFsM was sufficient to completely adsorb the targets, and the analytes retained on NFsM could be eluted by 1 mL of formic acid-ethyl acetate (containing 20% methanol) (1∶99, v/v). The residues were redissolved in 0.1 mL 10% methanol aqueous solution containing 0.2% formic acid. In addition, no adjustment of the pH and ionic strength of the sample solutions was required, and the breakthrough volume was 50 mL. The limits of detection (LODs) and limits of quantification (LOQs) of the six target compounds were measured at 3 times and 10 times the signal-to-noise ratio (S/N), respectively. The LODs and LOQs were 0.3-1.5 μg/kg and 1.0-5.0 μg/kg, respectively. The linear ranges of the six target compounds were LOQ-1000 μg/kg, and the coefficient of determination (R²) was greater than 0.999. To evaluate the accuracy and precision, blank spiked samples at three levels (low, medium, and high) were prepared for the recovery experiments, and each level with six parallel samples (n=6). The recoveries ranged from 94.37% to 102.82%, with intra-day and inter-day relative standard deviations of 2.38% to 8.06% and 4.10% to 9.10%, respectively. To evaluate the purification capacity of PDA-PS NFsM, the matrix effects before and after SPE were calculated and compared. Matrix effects before SPE were -12.98% to -38.68%. After the completion of SPEbased on PDA-PS NFsM, the matrix effect of each target analyte was significantly reduced to -2.15% to -7.36%, which proved the significant matrix removal capacity of PDA-PS NFsM. Finally, the practicality of this method was evaluated by using it to analyze real samples. This SPE method based on PDA-PS NFsM is efficient, practical, and environmentally friendly, and it has great potential for use in the routine monitoring of drug residues in fish.

Novel solid-phase extraction filter based on a zirconium meta-organic framework for determination of non-steroidal anti-inflammatory drugs residues

In this study, a zirconium-based metal-organic framework UiO-66-NH₂ modified cotton fiber (CF@UiO-66-NH₂) was fabricated for the extraction of five common NSAIDs, namely ketoprofen, naproxen, flurbiprofen, diclofenac sodium, and ibuprofen. UiO-66-NH₂ was synthesized and immobilized on the surface of cotton fiber using an environmentally friendly aqueous synthesis method. The prepared CF@UiO-66-NH₂ composite of 50 mg was loaded into a 13 mm recessed filter for use as a solid-phase extraction (SPE) adsorbent material. The filter was then used to enrich NSAIDs in fish and shrimp muscle tissues followed by ultra-high performance liquid chromatography (UPLC) detection. Several key parameters were evaluated and optimized, including adsorption flow rate, pH value of sample, desorption flow rate, and the formic acid content of the eluent. Under optimized conditions, linear ranges of ketoprofen, naproxen, flurbiprofen, diclofenac sodium, and ibuprofen were 2.0-300.0 ng/mL, 1.4-280.0 ng/mL, 3.0-400.0 ng/mL, 1.0-500.0 ng/mL, and 14.0-560.0 ng/mL, respectively. The detection limits ranged from 0.12 ng/mL to 3.50 ng/mL with recoveries in the range of 72.95-116.99%, RSDs < 9.90%. The results demonstrated that the homemade filters based on CF@UiO-66-NH₂ exhibited good reproducibility, stability and adsorption property for the determination of trace-level NSAIDs in complex matrix.

Nanoparticle-based polyacrylonitrile monolithic column for highly efficient micro solid-phase extraction of carotenoids and vitamins in human serum

In this work, a biocompatible monolithic column based micro-solid-phase extraction (µ-SPE) method was developed for biological fluid analysis. A novel nanoparticle-based polyacrylonitrile monolithic column (C30 NP-PMC) was fabricated by incorporating triacontyl (C30) modified silica nanoparticles (NPs) into the polyacrylonitrile monolithic matrix through thermally induced phase separation. With efficient mass transfer and sorption capacity, C30 NP-PMC exhibited outstanding performance for the extraction of carotenoids and fat-soluble vitamins (FSVs) from human serum samples, superior to commercial C18 cartridges as well as liquid-liquid extraction (LLE) method. Under optimal conditions, the proposed µ-SPE method coupled with high-performance liquid chromatography-diode array detection (HPLC-DAD) achieved satisfactory limits of detection (LODs) (1.5-75.0 ng/mL) and good recoveries (85.0-106.5 %) with relative standard deviations (RSDs) of less than 12.1% by consuming lower sorbent (35.0 mg) and organic solvent (0.8 mL). Successful application of the developed method demonstrated the great potential of such monolithic sorbents for efficient isolation and preconcentration of trace analytes from blood samples.

Morphology-maintaining synthesis of copper hydroxy phosphate@metal-organic framework composite for extraction and determination of trace mercury in rice

A novel copper hydroxy phosphate@MOF composite DMP-Cu decorated by 2, 5-dimercapto-1, 3, 4-thiadiazol was facilely prepared and characterized. A dispersive SPE strategy using DMP-Cu as adsorbent combined with atomic fluorescence spectroscopy was developed for the selective capture of trace total mercury in rice sample. The adsorption mechanism showed that the Hg²⁺ removal process was fitted with pseudo second-order kinetics and the Langmuir adsorption model. The adsorbent was easy to be regenerated and the maximum adsorption capacity for the removal of Hg²⁺ was 249.5 mg g^-1 at the optimal pH of 4. X-ray photoelectron spectroscopy and Raman spectra verified the selective and strong interaction between Hg²⁺ and thiol/nitrogen-containing functional groups of DMTZ on DMP-Cu. The trace total mercury in rice samples was determined with detection limit of 0.0125 ng mL^-1 and relative standard deviation below 6%. The high recoveries were obtained in range of 98.8-109% for the spiked rice samples.

Improved Solid-Phase Extraction for Simple, Sensitive, and Efficient Determination of Trace Plant Growth Regulators in Cherry Tomatoes by High-Performance Liquid Chromatography

The overuse of plant growth regulators (PGRs) in agricultural products has gradually increased in recent years, resulting in hazardous effects on food safety and human health. For the first time, a sensitive, accurate, and low-cost analytical method involving improved solid-phase extraction coupled with high-performance liquid chromatography was developed to determine trace PGRs in cherry tomatoes. Thereafter, the extraction mechanism and conditions were elucidated. Under optimized conditions, good linearity (0.04-400 ng g^-1; r ≥ 0.9996) and lower limits of detection (0.005-0.006 ng g^-1) were observed. The recoveries were 81.4-90.1%, with relative standard deviations of ≤6.7% (three levels). Finally, the developed method was successfully used to detect trace PGRs in cherry tomatoes. The results illustrated that this sensitive method shows great potential for application to monitor trace PGRs in agricultural products and, thus, provide technical support for food safety and public health.

Sodium 4-styrenesulfonate functionalized nanofibers mat as 96-well plate solid-phase extraction adsorbent for quantitative determination of multiple β-agonists residues in pork samples

In this work, sodium 4-styrenesulfonate functionalized polyacrylonitrile nanofibers mat (SS/PAN NFM) was firstly prepared and applied as 96-well plate solid-phase extraction adsorbent for quantitative determination of seven β-agonists residues in pork samples. The functional modification endowed the SS/PAN NFM with superior adsorption performance for target β-agonists. The adsorption process is spontaneous (ΔG < 0), the initial adsorption rate can reach 6.03-9.09 mg/g/min and the maximum adsorption capacity is calculated to be 48.3 mg/g at 298 K. Moreover, SS/PAN NFM can be reused for 12 times without degradation in adsorption capability. Combined with UPLC-MS/MS, the limits of detection can reach 0.006-0.24 μg/kg, the recoveries ranged from 87.2% to 111% and the relative standard deviations of intra-day and inter-day precisions were in the scope of 1.75%-11.6% and 5.08%-13.5%, respectively. The obtained results fully demonstrated the practicability of this method in preventing the hazard of β-agonists residues.