Solid-phase Extraction Adsorbent Research Articles

Synthesis of composite materials combining magnetic metal-organic frameworks and conjugated organic frameworks for selective extraction of carbendazim and thiabendazole residues from Chinese herbal medicine samples

A magnetic metal-organic framework MIL-68(Al) and a covalent organic framework were used as magnetic solid-phase extraction (MSPE) adsorbents in combination with high-performance liquid chromatography ultraviolet detection (HPLC-UV) to detect carbendazim (CBZ) and thiabendazole (TBZ). The main parameters affecting the extraction in the MSPE process were studied and optimized. Fe3O4@MIL-68(Al) coated with 1,3,5-tris(4-aminophenyl)benzene and terephthaldehyde (Fe3O4@MIL-68(Al)@TAPB-PDA-COF) was analyzed and verified. The material was proven to be suitable for adsorbing CBZ and TBZ. Various adsorption models were used to study its adsorption mechanism. The adsorption results were in good agreement with the pseudo-second-order kinetic model and Langmuir isotherm model. The maximum adsorption capacities of Fe3O4@MIL-68(Al)@TAPB-PDA-COF over CBZ and TBZ were 54.24 and 67.87 mg g−1, respectively, and the equilibrium adsorption time was 200 min. Fe3O4@MIL-68(Al)@TAPB-PDA-COF with excellent recyclability showed higher adsorption capacity and selectivity. A method based on Fe3O4@MIL-68(Al)@TAPB-PDA-COF combined with HPLC-UV was established under the optimal extraction conditions and used to separate and detect trace imidazole drugs in Chinese herbal samples, achieving a low limit of detection (0.65–1.30 μg L−1) with excellent linear correlation (r > 0.999). The recovery rate and relative standard deviation were 86.05–99.78 % and 0.15–4.90 %, respectively. Therefore, the Fe3O4@MIL-68@TAPB-PDA-COF can be regarded as an effective adsorbent for the pretreatment of CBZ and TBZ drugs in Chinese herbal samples.

Functionalized nanofibers mat prepared through thiol–ene “click” reaction as solid phase extraction adsorbent for simultaneous detection of florfenicol and paracetamol residues in milk

Due to the significant differences in physical and chemical properties of various veterinary drugs, sample pretreatment is still the bottleneck of simultaneous detection of multiple veterinary drug residues. In order to achieve quantitative determination of two different types of veterinary drug residues (florfenicol and paracetamol) in milk, 1-allyl-3-methylimidazolium chloride (AmimCl) functionalized nanofibers mat (AmimCl-NFsM) was prepared through thiol-ene “click” reaction and applied as a new solid phase extraction adsorbent. The preparation parameters were systematically investigated and optimized through dynamic adsorption experiments. The developed method achieved significant extraction and purification efficiency, which was attributed to the multiple adsorption mechanisms of AmimCl-NFsM. Under the optimal condition, the established method showed low detection limit (1.25–2.90 ng/mL), high precision (RSDs ≤ 12.6 %) and good recovery (76.4 %–96.1 % with RSDs ≤ 5.23 %). The obtained results demonstrated the practical application value of the established method in food safety field.

Preparation of double-system imprinted polymer-coated multi-walled carbon nanotubes and their application in simultaneous determination of thyroid-disrupting chemicals in dust samples

Dust ingestion is a significant route of human exposure to thyroid-disrupting chemicals (TDCs), and simultaneous determination of multi-contaminants is a great challenge for environmental monitoring. In this study, molecularly imprinted polymer-coated multi-walled carbon nanotubes using thyroxine as the template were synthesized for highly selective TDCs capture. This polymer was prepared by integrating the atom transfer radical polymerization using 2-(3-indol-yl)ethylmethacrylamide as the monomer with the self-polymerization of dopamine. Construction of double-system imprinted cavities could significantly improve their selective recognition performance for TDCs and the coincidence rate reached 88.5 %. The prepared polymers were applied as the solid phase extraction adsorbent to simultaneously determine 7 groups of 35 TDCs. The proposed method showed wide linear range (0.25–1000 ng L−1), low limits of detection (0.02–0.23 ng L−1) and acceptable recoveries (81.8 %–103.5 %). The occurrence and distribution of TDCs were then studied in indoor dust samples (n = 65) collected from four cities in China. We found that tetrabromobisphenol A was the predominant compound and perfluorinated compounds were the most abundant TDCs. In addition, the distribution ratio of TDCs varied between regions. This study provides an efficient technology for direct exposure assessment of multi-contaminants.

Room-temperature synthesis of ionic liquid@covalent organic frameworks for the solid phase extraction and analysis of six herbicides from water samples

Waters contaminated with pesticides poses a potential hazard to ecosystems and human health, so sensitive and efficient analytical methods are essential for water monitoring. Herein, in order to efficiently extract six commonly used herbicides, a novel ionic liquid covalent organic framework (IL@COF) was prepared using a simple room-temperature synthesis in this study. As an adsorbent for solid phase extraction (SPE), the mesoporous material exhibits rapid adsorption performance for six typical herbicides from water samples. Under the optimal experimental conditions, wide linearities (500 ∼ 20,000 μg L–1) and low limits of detection (prometryn: 17.9 μg L–1; metribuzin: 36.7 μg L–1; bentazon: 14.5 μg L–1; isoproturon: 18.0 μg L–1; acetochlor: 19.6 μg L–1; butachlor: 37.1 μg L–1) for six analytes were obtained via high performance liquid chromatography (HPLC). The adsorbent has stable physical and chemical properties and can be reused for 10 times after effective elution. The applicability of this method is further evaluated by analyzing ten kinds of real water sample. The recoveries of six kinds of herbicides ranged from 85.3 % to 122.9 %. The mechanism of adsorption is the interaction between hydrogen bond acceptor and donor. These results indicate that HPLC after SPE with a new type of IL@COF as the SPE adsorbent is a promising technique for the simultaneous detection of six pesticides in environmental water samples.

Dual-use ionization source for direct and sensitive detection of trace carbamates residue

Directly determining trace compounds in actual sample by ambient ionization mass spectrometry (AIMS) has always been a challenge. Due to the excellent adsorption and desorption properties of nanomaterials, AIMS combined with nanomaterials can improve the adsorption and desorption properties of MS. In this work, we developed a molecularly imprinted graphene oxide coated steel sheet (MIGOCS) to be used as a solid phase extraction adsorbent. Graphene oxide was characterized by its strong adsorption abilities, and the surface molecularly imprinted polymer has high selectivity. Here, the MIGOCS coupled with the ambient electrospray ion source was used to detect trace carbamate pesticides in water samples. Meanwhile, the extraction and spray parameters were systematically optimized. The newly developed molecularly imprinted graphene oxide-steel sheet spray-mass spectrometry (MIGO-SS-MS) method has low detection limits (0.05 ∼ 0.4 ng mL−1) and satisfactory recoveries (83.23 ∼ 97.98 %) for carbamates (CMs). The method can be potentially applied to the determination of CMs in water and food samples.

Hydroxyl and carboxyl group functionalized conjugated microporous nanomaterial as adsorbent for the solid-phase extraction of phenolic endocrine disrupting chemicals from freshwater fish samples

Endocrine disruption chemicals (EDCs) in food can seriously harm human health. In this study, a hydroxyl and carboxyl group functionalized conjugated microporous nanomaterial (CMP) was prepared by Friedel-Crafts reaction and used as solid-phase extraction (SPE) adsorbent. A functionalized CMP based SPE combined with high performance liquid chromatography-diode array detection was built for the determination of phenolic EDCs from nine fish samples. The extraction conditions were optimized by both single factor and response surface methodology (Box-Behnken Design). The established method performed well in terms of the response linearity (in the range of 0.50–100 ng g−1 with coefficient of determination larger than 0.9942), limits of detection (0.15–0.30 ng g−1, S/N of 3), limits of quantification (0.50–1.00 ng g−1, S/N = 10), method recoveries (78.4–121 %) and repeatability (relative standard deviation < 11 %). It can be used as an efficient method to detect trace phenolic EDCs in real fish samples.

Magnetic multi-walled carbon nanotubes assisted solid phase extraction and detection of neonicotinoid pesticides in honey and tea samples

In this study, magnetic multi-walled carbon nanotubes (MMWCNTs) were prepared by a one-pot solvothermal method. And they were used as the adsorbent of magnetic solid-phase extraction (MSPE) to extract NEOs. MMWCNTs exhibit good adsorption performance toward NEOs. The adsorption capacities for imidacloprid, thiacloprid, and acetamiprid are 18.4, 25.9, and 18.4 mg g−1, respectively. Also, the adsorption process takes 20 min. The adsorption isotherm fitted to the Langmuir model and the adsorption kinetics was well described by the pseudo-second-order kinetic model. Moreover, the adsorption mechanism was discussed. The MMWCNTs-based MSPE method was combined with field-enhanced sample stacking-capillary electrophoresis (FESS-CE) to realize the sensitive detection of NEOs. The detection limits of NEOs in honey and bottled green tea beverage samples ranged from 7.63 to 16.7 ng g−1. The recoveries were in the range of 84.5 ± 3.2 % to 99.2 ± 1.6 %, with relative standard deviations less than 5.5 %, suggesting the feasibility of the method in actual samples.

One-step preparation of a biphasic monolithic separation media for enriching and purifying lupeol in medicine plants

In this study, a monolith consisted of two materials with different separation modes were prepared by a one-step method at both ends of a column. Acrylic acid and 2-hydroxyethyl methacrylate (HEMA) were used as monomers for hydrophilic and hydrophobic parts, respectively. The total pore volumes and porosities of hydrophilic and hydrophobic materials were 3.1098 mL/g and 75.2535 %, 4.4380 mL/g and 72.5317 %, respectively. The prepared monolithic columns had excellent mechanical strength and good permeability, and can bear high flow rates up to 5 mL/min. The biphasic monolith functioned in two retention modes: hydrophilic interaction chromatography (HILIC) and hydrophobic interaction chromatography (HIC), and the dual-mode were realized by switching the ratio of acetonitrile in the mobile phase. The biphasic monolithic column was used as solid phase extraction (SPE) adsorbent for on-line enrichment and purification of lupeol in Chinese herbal medicines (CHM), which showed good adsorption performance and excellent reproducibility. The spiked recoveries were from 88.52 % to 93.68 % under the optimal experimental conditions; the repeatability could reach 100 times. The method showed good linearity in the range of 0.13 ∼ 2.00 × 103 μg /mL with a correlation coefficient of r = 0.9991; the limit of detection (LOD) was 0.023 μg/mL and the limit of quantification (LOQ) was 0.076 μg/mL; the intra-day and inter-day precisions were both less than 1.05 %.

Simultaneous detection of heterocyclic aromatic amines and acrylamide in thermally processed foods by magnetic solid-phase extraction combined with HPLC-MS/MS based on cysteine-functionalized covalent organic frameworks.

Acrylamide (AA) and heterocyclic aromatic amines (HAAs), as classic hazards produced during food thermal processing, have been widely concerned, but because of their polarity difference, it is very difficult to detect these contaminants simultaneously. Herein, novel cysteine (Cys)-functionalized magnetic covalent organic frameworks (Fe3O4@COF@Cys) were synthesized via a thiol-ene click strategy and then used as adsorbents for magnetic solid-phase extraction (MSPE). Benefiting from the hydrophobic properties of COFs and the modification of hydrophilic Cys, AA and HAAs could be enriched simultaneously. Then, a rapid and reliable method based on MSPE coupled with HPLC-MS/MS was developed for the simultaneous detection of AA and 5 HAAs in thermally processed foods. The proposed method showed good linearity (R2≥0.9987) with satisfactory limits of detection (0.012-0.210μgkg-1) and recoveries (90.4-102.8%). Actual sample analysis showed that the levels of AA and HAAs in French fries were affected by frying time and temperature, water activity of samples, content and type of reaction precursors, and reuse of oils.

Room-temperature synthesis of imine-linked magnetic covalent organic polymers in deep eutectic solvents for the extraction of flavonoids and their determination with HPLC-MS/MS.

A novel imine-linked magnetic covalent organic polymer, Fe3O4@TAB-TFPT, was synthesized using environmentally friendly deep eutectic solvents as the reaction medium instead of conventional organic solvents. The materials were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), FT-IR, N2 adsorption-desorption isotherms, energy dispersive spectrometer (EDS), X-ray photoelectron spectra (XPS), and thermo gravimetric analysis (TGA). Subsequently, the materials were employed as an adsorbent for magnetic solid-phase extraction (MSPE) of flavonoids, including Kurarinone, Norkurarinone, Xanthohumol, and Isoxanthohumol, prior to their determination by HPLC-MS/MS. The validation results demonstrate good linearity within the concentration range 0.1-1000ng∙mL-1 (R2 ≥ 0.9963), high enrichment factors ranging from 18.9 to 30.7, and low LODs (0.01-0.05ng∙mL-1) and LOQs (0.05-0.1ng∙mL-1). Furthermore, recoveries between 80.60% and 108.40% with relative standard deviations ≤ 8.49% were achieved. The proposed MSPE-HPLC-MS/MS method was successfully applied to the determination of flavonoids in Sophora flavescens Aition sample.

Preparation and evaluation of a tryptophan based hypercrosslinked porous polymer as an efficient adsorbent for pipette tip solid-phase extraction of sulfonamides

A novel tryptophan-based porous polymer is designed and synthesized via a facile one-step hypercrosslinking polymerization process, and applied as sorbent for extraction of trace sulfonamides in foodstuffs. The developed polymer has high surface area, large conjugate system, and abundant functional groups (e.g., π-π stacking, hydrogen bonding, hydrophobic and electrostatic attraction interactions), which endow it with superior affinity and high adsorption capacity for sulfonamides (16.16–59.29 mg g−1). The optimized SPE method is coupled with HPLC-DAD to create a sensitive and efficient protocol that provides good linearity (R2 ≥ 0.9979), low limits of detection, satisfactory recoveries (92.5–109.5 %) and high precisions (RSDs < 8.24). In addition, the newly proposed method greatly reduces the amount of adsorbent (2.0 mg) and organic solvent (2.0 mL) used. Adsorption kinetics, isotherms, and simulation calculations studies further reveal the presence of monolayer adsorption, chemical adsorption process, and multiple interactions. Thus, this work presents a polymer capable of multiple interactions for the pretreatment of trace sulfonamides in foodstuffs.

Metal-organic frameworks modified melamine foam in pipette-tip for rapid solid-phase extraction of organophosphorus pesticides in fruits and vegetables.

In this work, metal-organic frameworks (MOFs) including Fe-MIL-101 and Ti-MIL-125 were prepared and fixed on the melamine foam (MF) by polyvinylidene fluoride (PVDF) to prepare MF/PVDF/MOFs, which was used as adsorbents in pipette-tip solid-phase extraction (PT-SPE) for rapid extraction of organophosphorus pesticides (OPPs). Then, a gas chromatograph-flame thermionic detector (GC-FTD) was used for simultaneous analysis of Dimethoate (DMT), Iprobenfos (IBF), Parathion-methyl (PAM), and Chlorpyrifos (CPF). The morphology, crystal structure, and functional groups of MF/PVDF/MOFs were characterized, indicating that Ti-MIL-125 and Fe-MIL-101 were successfully synthesized and distributed on MF. The Fe-MIL-101 and Ti-MIL-125 showed good extraction ability for OPPs, which was mainly due to the π-π interaction and the multiple porous structures. Under the optimal conditions, the limit of detection (LODs) of four OPPs was 0.03-0.14μg L-1 and the RSDs were less than 9.9%. The developed PT-SPE method showed a short extraction time (<3min). The recoveries in fruits and vegetables (Celery, cabbages, and oranges) ranged from 75.3%-118.8% (RSDs<9.6%). The prepared MF/PVDF/MOFs demonstrated the efficient extraction performance of OPPs, contributing to the rapid pretreatment of OPPs from food and the environment.

Synthesis of magnetic covalent organic framework composites for effective extraction of benzimidazole fungicides from food samples

Benzimidazoles (BZDs) are widely applied and easily accumulated through the food chain and endanger human health. Effective sample pre-treatment technology is the key procedure for trace BZDs analysis. Herein, magnetic covalent organic frameworks (Fe3O4@TRITER) nanospheres, as magnetic solid-phase extraction (MSPE) adsorbent, were synthesized and well characterized. The efficient extraction of BZDs residues depended on large specific surface of COFs and π-π and hydrophobic interactions between TRITER shell and BZDs. Under the optimal MSPE conditions, the developed MSPE-HPLC based on Fe3O4@TRITER method for BZDs residues afforded good linearities (0.01–1 μg mL−1) with R2 (≥0.996) and low limit of detections (3 ng mL−1). The developed Fe3O4@TRITER based MSPE-HPLC method was evaluated and successfully applied to determine BZDs residues in orange juice, mixed juice drink and cucumber with satisfactory recoveries (76.9–117 %) and relative standard deviations (0.10–7.90 %).

Facile synthesis of spherical covalent organic frameworks for enrichment and quantification of aryl organophosphate esters in mouse serum and tissues.

Here, an imine-linked-based spherical covalent organic framework (COF) was prepared at room temperature. The as-synthesized spherical COF served as an adsorbent in dispersive solid-phase extraction (dSPE), by its virtue of great surface area (1542.68 m2 /g), regular distribution of pore size (2.95nm), and excellent stability. Therefore, a simple and high-efficiency dispersive solid phase extraction method based on a spherical COF coupled with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established to determine aryl organophosphate esters in biological samples. This approach displayed favorable linearity in the range of 10.0-1000.0ng/L (r>0.9989), a high signal enhancement factor (58.8-181.8 folds) with low limits of detection (0.3-3.3ng/L). Moreover, it could effectively eliminate complex matrix interference to accurately extract seven aryl organophosphate esters from mouse serum and tissue samples with spiked recoveries of 82.0%-117.4%. The as-synthesized spherical COF has been successfully applied in sample preparation. The dSPE-HPLC-MS/MS method based on a spherical COF has potential application to study the pollutants' metabolism in vivo.

Fabrication of a magnetic metal-organic framework/covalent organic framework composite for simultaneous magnetic solid-phase extraction of seventeen trace quinolones residues in meats

Effective capture of quinolones (QNs) in animal-derived food is a vital procedure for food safety monitoring. However, the lack of adsorption specificity and difficult to recycle in complex substrate conditions have been major problems for most of the adsorbents. In this work, a magnetic Fe3O4/MOF/COF composite (named Fe3O4@NH2−MIL-125@TpPa-SO3H) was successfully synthesized with good magnetic responsiveness and conspicuous affinity towards QNs. The Fe3O4/MOF/COF composite was used as a magnetic solid-phase extraction (MSPE) adsorbent for pretreatment and determination of QNs in meat samples. Under optimal MSPE conditions in combination with high performance liquid chromatography-quadrupole orbitrap high resolution mass spectrometer (HPLC-Q-Orbitrap HRMS), the proposed method had good linearity (R2 ≥ 0.9978) from 0.01 to 100ng g−1, low limits of detection (0.0016 to 0.0940ng g−1), good precision with relative standard deviations lower than 5.8%. This method was effectively applied to the detection of 17 QNs in the spiked pork, chicken and beef samples with satisfactory recoveries from 83.9 to 106.2%. The separation selectivity mainly due to the π–π interaction, hydrogen bonding, and electrostatic attraction between QNs and the sulfonic acid and amino functional groups of the composite. After verification, the stability and reusability of the composite meet the requirements of complex matrix sample pretreatment. The developed MSPE method based on the magnetic Fe3O4/MOF/COF composite provided an ideal sample pretreatment alternative for determining trace QNs in complex matrixes with selectivity, simplicity, rapidity, and efficiency.

Reduced graphene oxide-zinc iron oxide nanomaterial as selective dispersive solid-phase extraction sorbent for extraction and enrichment of aflatoxins from milk combined with UHPLC-MS/MS analysis

Fungal species capable of producing aflatoxins frequently contaminate the feed provided to dairy animals, leading to the subsequent occurrence of aflatoxin contamination in milk. Milk is renowned for its exceptional nutritional composition, and the consumption of milk contaminated with aflatoxins by humans can engender a multitude of health complications. In this study, reduced graphene oxide zinc iron oxide (rGO-Zn/Fe2O4) nanomaterial was utilized as a dispersive solid phase extraction adsorbent to separate and enrich aflatoxins (aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2, and aflatoxin M1) from milk. The rGO-Zn/Fe2O4 nanomaterial was morphologically characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, indicating that Zn/Fe2O4 nanoparticles were embedded on the surface of rGO. The acetonitrile/formic acid (99/1, v/v) combined with ultrasonic treatment for a duration of 40 min expressed an efficient extraction solvent. Employing the matrix-spiked technique, different parameters of the dispersive solid-phase extraction (d-SPE) method were meticulously optimized, yielding the following conditions: 2% acetonitrile as loading solvent, 15 mg of rGO-Zn/Fe2O4 as the adsorbent quantity, 15 min of ultrasonication as adsorption time, and n-hexane as the washing solvent. The desorption reagent was 5 mL acetonitrile, with a desorption time of 5 min. The combination of the dispersive solid-phase extraction (d-SPE) technique with validated UHPLC-MS/MS quantitative analysis demonstrated excellent selectivity, a robust linear relationship (R2 ≥ 0.994), remarkable sensitivity (limit of quantification ranging from 0.006 to 0.013 µg/L), and satisfactory recovery rates of 78%–104% at three different matrix-spiked levels. Moreover, the method exhibited precision with relative standard deviations (RSD) ranging from 2.4% to 10.8%. Following appropriate pretreatment procedures, the milk samples underwent rigorous aflatoxin analysis, leading to the identification of AFM1 presence in all of the examined milk samples (n = 9). However, the contamination levels detected were found to be within the permissible limits as defined by regulatory standards.

Highly efficient enrichment of eugenol anesthetics in aquatic products using magnetic nanospheres decorated covalent organic framework microflowers

Herein, uniform magnetic covalent organic framework (MCOF) microflowers were synthesized by facile inlaying aldehyde-functionalized Fe3O4 nanoparticles onto the COF under mechanical stirring at room temperature. The MCOF microflowers kept flower-shaped morphology with high crystallinity and magnetism. In addition, the good water dispersibility and reusability made the MCOF microflowers to be good magnetic solid phase extraction (MSPE) adsorbents for the high-efficiency enrichment of eugenol anesthetics from aquatic products. The MCOF microflowers showed fast adsorption rate (10 min) and high extraction efficiency (above 84.02%) for eugenol anesthetics under optimal conditions. The MCOF microflowers displayed maximum adsorption capacities of 6.67, 12.31, and 16.78 µg g−1 for eugenol, eugenol acetate, and methyl isoeugenol, respectively. The MCOF microflowers based MSPE coupled with high-performance liquid chromatography method was proposed for enrichment and analysis of eugenol anesthetics in tilapia, shrimp and crab samples. The method showed a wide linear of 5.0–500.0 µg kg−1 and low detection limits of 2.4–3.6 μg kg−1 for eugenol anesthetics. The recoveries of spiked eugenol anesthetics ranged from 80.0% to 118.8% with relative standard deviations no>9.2%. Results indicate the high potential of MCOF microflowers to be an adsorbent for efficient extraction and analysis of eugenol anesthetics from complex aquatic product samples.

One-pot preparation of magnetic molecularly imprinted adsorbent with dual template molecules for simultaneously specific capture of sulfonamides and quinolones in water and milk samples

Specific capture is a beneficial tactic in simultaneous monitoring of sulfonamides (SAs) and quinolones (QLs). For this purpose, a new magnetic molecularly imprinted adsorbent based on double-template molecules (DT-MIP@MNA) was facilely prepared by “one-pot” hydrothermal technique and utilized as the adsorbent of magnetic solid-phase extraction (MSPE). Molecular simulation technique was employed to quickly screen functional monomer. The recognition factors of prepared adsorbent towards templates sulfamethazine and nalidixic acid were 5.89 and 2.90, respectively, and the corresponding adsorption capacities were as high as 8.85 mg/g and 8.97 mg/g, respectively. Under the optimized parameters, the proposed DT-MIP@MNA/MSPE was combined with HPLC to simultaneously and selectively monitor trace SAs and QLs residuals in water and milk samples. The achieved limits of detection were 0.012–0.028 μg/L and 0.015–0.032 μg/kg for water and milk samples, respectively. The current supplied a sensitive, reliable and anti-interference method for simultaneously monitoring trace SAs and QLs in food.

Biochar/sodium alginate mixed matrix membrane as adsorbent for in-syringe solid-phase extraction towards trace nitroimidazoles in water samples prior to ultra-high-performance liquid chromatography-tandem mass spectrometry analysis.

In the present work, the herb (Poria cocos (Schw.) Wolf) residue, as an environmentally friendly and renewable biomass source, was converted into novel biochar. Biochar/sodium alginate mixed matrix membrane was fabricated. On this basis, a biochar/sodium alginate mixed matrix membrane-based in-syringe solid-phase extraction was developed combined with ultra-high performance liquid chromatography-tandem mass spectrometry to determine nitroimidazoles in water samples. The factors including times of exaction, type, and volume of elution solvent, and sample solution pH were thoroughly optimized. Then the correlation coefficient was 0.9995-0.9997. The limit of detection of four analytes was between 0.006 and 0.014ng/mL, and the recovery was between 79.02% and 99.1%. Consequently, the established method would provide a new perspective on monitoring nitroimidazoles in water samples.

Progress in the application of novel nano-materials to the safety analysis of agricultural products

The quality and safety of agricultural products are strongly related to human livelihood. Thus, the government and consumers have recently paid increased attention to the quality and safety of agricultural products. The development of efficient, rapid, and sensitive analytical methods for detecting pesticides, veterinary drugs, heavy metals, mycotoxins, and environmental pollutants in agricultural products is of great significance. Owing to the complexity of many sample matrices and the low concentration of pollutants in a typical sample, appropriate sample pretreatment steps are necessary to enrich pollutants in agricultural products. Solid-phase extraction (SPE) is the most widely used sample pretreatment technology; in this technique, the adsorbent generally determines the selectivity and efficiency of the extraction process. An increasing number of novel materials have been used as SPE adsorbents. The extraction efficiency, extraction selectivity, and analytical throughput of SPE could be greatly improved by combining these novel materials with various extraction modes (e. g., solid-phase microextraction, dispersed SPE, and magnetic SPE (MSPE)) during sample preparation. Because of their large specific surface area and high affinity toward target analytes, nanomaterials are often used as SPE adsorbents, thereby greatly improving the selectivity and sensitivity of the analytical technology. More importantly, these materials have become a priority area of research on preconcentration technologies for trace compounds in agricultural products. This paper summarizes the adsorption characteristics of several new nanomaterials, including magnetic materials, carbon-based materials, metal nanomaterials (MNs), metal oxide nanomaterials (MONs), metal organic frameworks (MOFs), and covalent organic frameworks (COFs). These nanomaterials present numerous advantages, such as large specific surface areas, high adsorption capacities, and tailorable structural designs. MSPE employs magnetic materials as sorbents to afford fast dispersion and efficient recycling when applied to complex sample matrices under an external magnetic field. The use of MSPE can avoid several typical problems associated with SPE such as poor adsorbent packing and high pressure, thereby greatly simplifying the pretreatment process and providing a high flux for sample analysis. Carbon-based materials are powdered or bulk nonmetallic solid materials with carbon as the main component; carbon and nitrogen materials, mesoporous carbon, carbon nanotubes, and graphene are some examples of these materials. These materials provide large specific surface areas, abundant pore structures, good thermal stability, high mechanical strength and adsorption capacity, and controllable morphology. Pure and modified carbon nanomaterials have been successfully used to purify target analytes from agricultural products. Given their unique physical and chemical properties, MNs and MONs have attracted significant interest for use in sample preparation. MNs and MONs with excellent thermal and mechanical stabilities show good resistance to a wide pH range and diverse organic solvents, which is crucial in adsorbent-based extraction methods. The surface of these materials can be easily modified with various ligands to improve their selectivity. MOFs and COFs present many advantages such as large specific surface areas, high porosity, adjustable pore performance, and good thermal stability. Several methods that employ novel adsorbent materials to analyze pollutants in a variety of agricultural products, such as chromatography, spectroscopy, mass spectrometry, and other detection technologies, have been established. This paper also reviews the application of adsorbent materials in the analysis of agricultural product quality and safety, and discusses the future development trends of these sorbents in sample preparation for the safety analysis of agricultural products.