The dual-configured hydrogen bonds induced by polymerized deep eutectic solvents-modified magnetic biochar enhanced the selectivity for 3,4-methylenedioxymethamphetamine.

The accurate discovering and monitoring of 3,4-methylenedioxymethamphetamine (MDMA) are especially important because of its substantial toxicity and potential harm to human and the ecological systems. Three types of polymerized deep eutectic solvents functionalized magnetic biochar (MBC@poly (AA/AAC/AAm-ChCl)) were successfully synthesized to adsorb MDMA. The isotherm and kinetic data confirmed that MBC@poly (AAm-ChCl) had the strongest adsorption capacity, and the order of adsorption capacity is as follow: MBC@poly(AAm-ChCl) > MBC@poly(AA-ChCl) > MBC@poly(MAA-ChCl), which also revealed that the adsorption was heterogeneous multi-layer chemisorption. The findings of the characterizations manifested that MBC@poly(AAm-ChCl) was the optimal adsorbent owning to its higher nitrogen content, resulting in the formation of a greater number of hydrogen bonds. Due to the strong hydrogen bonding effect of CO and -NH2 functional groups, MBC@poly(AAm-ChCl) exhibited the high selectivity towards MDMA under the coexistence of multiple chemical substances, and excellent adsorption performance over the pH range of 4-11. Urea as a hydrogen bond inhibitor further confirmed MBC@poly(AAm-ChCl) had high-density active hydrogen bonding sites. Furthermore, utilizing density functional theory (DFT) for simulating adsorption both before and after the process verified that the high selectivity of MBC@poly(AAm-ChCl) attributed to the formation of the dual-configured hydrogen bonds. This study provides support for the production of highly selective biochar for use in pretreatment during drug detection.

Efficient magnetic solid-phase extraction, UPLC-MS/MS detection, and consumption assessment of five trace psychoactive substances.

Wastewater-based epidemiology (WBE) has become an objective and updated surveillance strategy for monitoring and estimating consumption trends of psychoactive substances (PSs) in the population. Firstly, magnetic shrimp shell biochar-based adsorbent (DZMBC) was synthesized and employed for extraction trace PSs from municipal wastewater. Proper pyrolysis temperature and increased KOH activator content favored the pore structure and surface area, thus facilitating extraction. DZMBC delivered exceptional extraction performance such as pH stability, anti-interference property, fast magnetic separation ability, reusability, and reproducibility. Then, a method based on magnetic solid-phase extraction (MSPE) followed by ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed, validated, and utilized for the quantitative determination of five PSs in real wastewater samples. Methodological validation results indicated a favorable linearity, low method limits of detection (1.00-4.75 ng/L), and good precisions (intra-day and inter-day relative standard deviations < 4.8%). Finally, an objective snapshot of Chongqing drug use and consumption pattern was obtained. Methamphetamine (MAMP) and 3,4-methylenedioxymethamphetamine (MDMA) were the prevalent illegal drugs in local. Both concentrations and per capita consumption of MDMA displayed a change (P < 0.05) between July and September, while no statistical differences were observed for each week.

Red/NIR-I-Fluorescence Carbon Dots Based on Rhein with Active Oxygen Scavenging and Colitis Targeting for UC Therapeutics.

Ulcerative colitis (UC) is a chronic inflammatory disease with uncontrolled inflammation and demage to the intestinal barrier. Rhein, a bioactive compound in traditional Chinese medicine, has anti-inflammatory and intestinal repair effect. However, their clinical application is limited by their hydrophobicity and poor bioavailability. L-arginine, as a complement to NO, has synergistic and attenuating effects. In this paper, red/NIR-I fluorescent carbon dots based on rhein and doped with L-arginine (RA-CDs), which are synthesized by a hydrothermal process without any organic solvents, are reported. RA-CDs preserve a portion of the functional group of the active precursor, increase rhein solubility, and emit red/NIR-I light for biological imaging. In vitro experiments show that RA-CDs scavenge excessive reactive oxygen species (ROS), protect cells from oxidative stress, and enable the fluorescence imaging of inflamed colons. In a DSS-induced UC mouse model, both delayed and prophylactic treatment with RA-CDs via intraperitoneal and tail vein injections alleviate UC severity by reducing intestinal inflammation and restoring the intestinal barrier. This study highlights a novel strategy for treating and imaging UC with poorly soluble small-molecule drugs.

Evaluation of the difference in adsorption of amphetamine-type drugs on deep eutectic solvent-functionalized graphene oxide/ZIF-67 composite: Experiment and theoretical calculations.

Herein, the capture and separation properties of the deep eutectic solvent-functionalized magnetic graphene oxide/ZIF-67 composite (ZMG-DES) towards amphetamine-type drugs (MDMA, MAM and AM) from water were investigated. Kinetic and isotherm models showed that the adsorption behaviors were monolayer chemisorption. Batch experiment results showed that the maximal adsorption of MDMA (933.652 µg⋅g-1) was 2.3 and 2.8 times higher than that of MAM (412.849 µg⋅g-1) and AM (328.652 µg⋅g-1), respectively, and this superiority remained consistent under varied environmental influences (pH, background ion and humic acid). Theoretical calculations and characterization analyses demonstrated the methylenedioxy group of MDMA led to the highly selective adsorption. Electrostatic potential (ESP) distribution indicated that the methylenedioxy added electron-rich areas and provided more adsorption sites. The Independent Gradient Model (IGMH) quantified the adsorption contribution of the functional groups in each system, which the contribution of the methylenedioxy reached 25.23%, significantly exceeding that of -NH- (18.80%) and benzene ring (20.76%), and proved that the H-bonds formed methylenedioxy enhanced adsorption. Furthermore, the Hirshfeld surface analysis proved that the methylenedioxy and -NH- of MDMA acted as H-bond acceptor and donor, respectively, which synergistically promoted the adsorption. The present study will help us to understand the structure-property relationship between amphetamine-type drugs and ZMG-DES.

How hydrogen bonding and π-π interactions synergistically facilitate mephedrone adsorption by bio-sorbent: An in-depth microscopic scale interpretation.

Mephedrone (4-methylmethcathinone, MEPH) exhibited severe ecologic hazards and health detriments. A novel deep eutectic solvent functionalized magnetic ZIF-8/hierarchical porous carbon (DMZH) with excellent selectivity, interference resistance and recyclability, was developed for the rapid adsorption of MEPH. Initially, potential adsorption sites of MEPH were predicted. Then, π-π and hydrogen bonding interactions were proposed and verified from characterizations, comparative experiments and theoretical calculations. The synergistic effects of the hydrogen bonding and π-π interactions increased the adsorption energies from -15.26 kcal⋅mol-1 to -21.83 kcal⋅mol-1, enhanced the degree of π-dissociation, enlarged the π-π isosurface area, extended the van der Waals surface mutual penetration distance, achieving stronger affinity and remarkable adsorption. Furthermore, offset (parallel-displaced) π-π stacking form existed between DMZH and MEPH. DMZH acted as the hydrogen bond donor and MEPH served as the hydrogen bond acceptor to form O-H⋯O and N-H⋯O hydrogen bonding interaction. Profiting from the synergistic effects, DMZH showed satisfactory adsorption for MEPH within 20 min with a maximum adsorption capacity of 3270.11 µg∙g-1, displayed excellent performance in wide pH range of 5∼11 and in the coexistence of multi-chemicals.

Adsorption of amphetamine on deep eutectic solvents functionalized graphene oxide/metal-organic framework nanocomposite: Elucidation of hydrogen bonding and DFT studies.

The efficient and selective removal of amphetamine (AMP) from water bodies is significant for environmental remediation. In this study, a novel strategy for screening deep eutectic solvent (DES) functional monomers was proposed based on density functional theory (DFT) calculations. Using magnetic GO/ZIF-67 (ZMG) as substrates, three DES-functionalized adsorbents (ZMG-BA, ZMG-FA, and ZMG-PA) were successfully synthesized. The isothermal results showed that the DES-functionalized materials introduced more adsorption sites and mainly contributed to the formation of hydrogen bonds. The order of the maximum adsorption capacity (Qm) was as follows: ZMG-BA (732.110 µg⋅g-1) > ZMG-FA (636.518 µg⋅g-1) > ZMG-PA (564.618 µg⋅g-1) > ZMG (489.913 µg⋅g-1). The adsorption rate of AMP on ZMG-BA was the highest (98.1%) at pH 11, which could be explained by the less protonation of -NH2 from AMP being more favorable for forming hydrogen bonds with the -COOH of ZMG-BA. The strongest affinity of the -COOH of ZMG-BA for AMP was reflected in the most hydrogen bonds and the shortest bond length. The hydrogen bonding adsorption mechanism was fully explained by experimental characterization (FT-IR, XPS) and DFT calculations. Frontier Molecular Orbital (FMO) calculations showed that ZMG-BA had the lowest HOMO-LUMO energy gap (Egap), the highest chemical activity and the best adsorption capability. The experimental results agreed with the results of theoretical calculations, proving the validity of the functional monomer screening method. This research offered fresh suggestions for the functionalized modification of carbon nanomaterials to achieve effective and selective adsorption for psychoactive substances.

Enhanced adsorption of 3,4-methylenedioxymethamphetamine by magnetic graphene oxide-polydopamine nanohybrid modified zeolitic imidazolate framework-67 and its micro-mechanism: Experiments and calculations.

Exploring the structure-dependent adsorption mechanism of contaminants in wastewater is beneficial to high-efficiency adsorbents design and environmental remediation. In this study, emerging porous material of zeolitic imidazolate framework-67 (ZIF-67) has been modified by the magnetic graphene oxide-polydopamine nanohybrid (mGOP) to obtain three-dimensional ZIF-67/mGOP through an in-situ growth strategy, which was applied to adsorb 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") in wastewater. A combination of characterizations, experiments (pH, humic acid and ion strength effect) and quantum chemical calculations revealed the microscopic adsorption mechanism involves each single component, of which the hydrogen bond (O/N…HO) and π-π electron donor acceptor (π-π EDA) interactions of mGOP endowed favourable adsorption of ZIF-67/mGOP, and mechanisms of the pore filling and Co-O chelation of ZIF-67 played synergistic effect. Such nanocomposite as a ZIFs-based adsorbent exhibited ultra-high porosity (total pore volume = 0.4033 cm3/g) and specific surface area (995.22 m2/g), revealed the heterogeneity and multilayer adsorption properties, and obtained a theoretical maximum adsorption capacity of 159.845 µg/g which higher than that of mZIF-67 alone. Overall, this work provided an effective strategy for rationally modulate ZIFs-based composites and exploration of adsorption mechanism.

Deep insight into selective adsorption behavior and mechanism of novel deep eutectic solvent functionalized bio-sorbent towards methcathinone: Experiments and DFT calculation.

This work designed and synthesized novelly selective, highly efficient and friendly environmental biochar nanomaterial (ZMBC@ChCl-EG) by screening suitable deep eutectic solvent (DES) as the functional monomer via Density Functional Theory (DFT). The prepared ZMBC@ChCl-EG achieved the highly efficient adsorption of methcathinone (MC) and exhibited excellent selectivity as well as good reusability. Selectivity analysis concluded that the distribution coefficient value (KD) of ZMBC@ChCl-EG towards MC was 3.247 L/g, which was about 3 times higher than that of ZMBC, corresponding to stronger selective adsorption capacity. The studies of isothermal and kinetics indicated that ZMBC@ChCl-EG had an excellent adsorption capacity towards MC and the adsorption was mainly chemically controlled. In addition, DFT was used to calculate the binding energies between MC and each component. The binding energies were -10.57 kcal/mol for ChCl-EG/MC, -3.15∼-9.51 kcal/mol for BCs/MC, -2.33 kcal/mol for ZIF-8/MC, respectively, suggesting that DES played a major role in enhancing methcathinone adsorption. Lastly, the adsorption mechanisms were revealed by variables experiment combined with characterizations and DFT calculation. The main mechanisms were hydrogen bonding and π-π interaction.

Enhanced adsorption of malathion and phoxim by a three-dimensional magnetic graphene oxide-functionalized citrus peel-derived bio-composite.

By integrating the steps of direct magnetization and one-pot pyrolysis, a three-dimensional (3D) magnetic graphene oxide-functionalized citrus peel-derived bio-composite (mGOBC) was synthesized and characterized successfully, and it was proved to possess a three-dimensional (3D) porous architecture and graphitic structure. Its potential as an enrichment adsorbent was investigated using adsorption kinetics and adsorption isotherm models to establish an effective analytical method for the determination of organophosphorus pesticides (OPPs) in vegetables. The experimental results indicated that the adsorption was better fitted with the pseudo second order model and Langmuir isotherm model, and the maximum adsorption capacities for malathion and phoxim were 25.26 mg g-1 and 42.31 mg g-1, respectively. It was found that the graphitic structure of mGOBC resulted in π-π EDA (electron donor-acceptor) interaction with the benzene rings, electron-donating N, P, and S atoms in the analytes, which assisted adsorption. Subsequently, Plackett-Burman (P-B) experimental design, central composite design (CCD) and response surface methodology (RSM) were employed to develop an analytical method based on the mGOBC adsorbent. Under optimal conditions, the developed method is accurate and precise. The novel synthesized mGOBC can efficiently achieve removal and trace determination of harmful OPPs.

One-step fabrication of alkali-acid modified three-dimensional magnetic biochar for the determination of pesticides in pigment-rich vegetables.

Magnetic biochar was successfully synthesized via a one-step method through simultaneous activation and magnetization with alkali-acid modified citrus peel as the raw material, which could effectively penetrate interfering substances. The characterization analysis showed that the magnetic biochar exhibited high graphitic degree, higher specific surface area and smaller pore diameter, which resulted in superior adsorption performance. The magnetic biochar was used as an adsorbent for the cleanup and extraction of 22 pesticides (consisting of insecticides, fungicides and herbicides) from vegetables and the quantitative detection was completed by gas chromatography-mass spectrometry (GC-MS). The Plackett-Burman experimental design (PBD), central composite design (CCD) and response surface methodology (RSM) were employed to identify significant factors and optimal experimental conditions. Under optimal conditions, the methodological linearity was in the range of 1-100 µg kg-1 with the coefficients of determination ranging from 0.9969-0.9999, while the limits of detection (LODs) and limits of quantification (LOQs) were 0.31-0.91 µg kg-1 and 1.03-3.05 µg kg-1, respectively. The recoveries of the analytes from spiked samples were in the range of 78.1-112.5%. It was confirmed that the method established by using magnetic graphitic biochar as the adsorbent is an efficient pretreatment procedure and could be successfully applied for analysis of food safety.

Multifunctional magnetic chitosan-graphene oxide-ionic liquid ternary nanohybrid: An efficient adsorbent of alkaloids.

A magnetically and recyclable multifunctional nanohybrid adsorbent (IL-Fe3O4@SiO2@CS/GO) with chitosan, graphene oxide and ionic liquid was prepared by glutaraldehyde cross-linking reaction, acylation reaction and directly grafted method. The incorporation of CS, GO and IL could collaboratively enhance adsorption for 5 alkaloids. The Box-Benhnken design was applied to optimize the experimental parameters affecting the extraction efficiency. The adsorption kinetic was further used to describe the adsorption process, revealing alkaloids adsorption was a chemisorption process, which was well represented by pseudo-second-order model. Concerning the equilibrium behavior, the adsorption was multilayer and heterogeneous adsorption that satisfactorily modeled by the Freundlich model. Under optimal conditions, good adsorption capacity for morphine, codeine, ephedrine, amphetamine and benzoylecgonine (7.2, 8.4, 9.2, 5.8 and 11.2 mg g-1, respectively) were obtained via multiple mechanisms to attain simultaneous extraction of alkaloids. Accordingly, IL-Fe3O4@SiO2@CS/GO nanohybrid adsorbent could be extended as a potential adsorbent for extraction of illicit additives in food samples.

Chitosan functionalized magnetic graphene oxide nanocomposite for the sensitive and effective determination of alkaloids in hotpot.

Chitosan functionalized magnetic graphene oxide nanocomposite (Fe3O4@SiO2@CS/GO) was successfully fabricated via a facile amide reaction between chitosan and graphene oxide. A novel extraction method using Fe3O4@SiO2@CS/GO as nanoadsorbent was developed and applied to the efficient extraction and determination of multiple alkaloids from the complex matrix. The composition and structure of the nanoadsorbent was systematically characterized by various techniques. The nanoadsorbent possesses performances of high efficiency, easy operation, superparamagnetism, environment friendly and economic feasibility. The adsorption mechanism for alkaloids included π-π electron-donor-acceptor interaction, cation-π interaction and hydrogen bonding. The principal parameters influencing extraction procedure such as adsorbent dosage, pH, adsorption time, desorption conditions and regeneration cycles were investigated and optimized. Under the optimized conditions, the method exhibited good linear dynamic range with correlation coefficient (r2) higher than 0.997 and the limit of detection (LOD) was among 0.016--0.092 µg kg-1. Intra- and inter-day relative standard deviations (RSDs) were <10%. These results indicated that the developed method was successfully applied for simultaneous detection of alkaloids in hotpot. This study provided valuable guidance and effective method for the analysis of alkaloids in intricate interference system.

A three dimension magnetic bio-char composite-based quick, easy, cheap, effective, rugged and safe method for multi-pesticides analysis of vegetables.

To improve the efficiency of high-throughput analysis, a three-dimensional (3D) magnetic Fe3O4-biochar composite was synthesized and used as adsorbent of QuEChERS pretreatment method for the analysis of 49 pesticide residues in vegetables containing complex pigments. The structure evolution mechanism of Fe3O4-biochar was discussed and the structural morphology was confirmed by a series of characterization methods. Multivariate approach was employed to optimize the extraction parameters including sample amount, solvent volume, NaCl amount, extraction time, anhydrous MgSO4 amount, adsorbent amount, purification time. The results revealed that extraction time and Fe3O4-biochar amount had significant influences on the recovery yield of pesticides and the 20 min extraction time and 13.9 mg Fe3O4-biochar are optimal conditions. Under these conditions, the Fe3O4-biochar exhibited better cleanup of matrix co-extracts than conventional adsorbents, which reduced matrix effect and simplified extraction process. Moreover, the adsorption mechanism was further probed and turned out that the aromatic sheets on Fe3O4-biochar dominated the π-π EDA (electron donor-acceptor) interaction for interfering substances. The proposed extraction method exhibited good linearity with correlation coefficient greater than 0.9902. The limits of quantitation (LOQs) were in the range of 0.03-0.67 µg kg-1. The average recoveries were between 81.3% and 117.3% with relative standard deviation (intra-day RSD = 0.5-7.5% and inter-day RSD = 0.6-6.9%). All results highlighted the excellent potential of Fe3O4-biochar strategy in analysis of pesticide residues in vegetables containing complex pigments.

A novel Fe3O4/graphene oxide/citrus peel-derived bio-char based nanocomposite with enhanced adsorption affinity and sensitivity of ciprofloxacin and sparfloxacin.

To create more active adsorption sites on biochar, the Fe3O4/GO/citrus peel-derived magnetic bio-nanocomposite (mGOCP) with hierarchically porous architectures was synthesized by a facile one-pot hydrothermal approach for efficient removal of fluoroquinolone antibiotics ciprofloxacin (CIP) and sparfloxacin (SPA). The characterization analysis of bio-nanocomposites showed that the incorporation of GO could ensure relatively higher surface area (1556 cm2 g-1), more abundant pore structure, and higher thermal stability within mGOCP bio-nanocomposites than Fe3O4/citrus peel-derived magnetic bio-nanocomposites (mCP). And the mGOCP-1% attained outstanding adsorption capacity for CIP (283.44 mg g-1) and SPA (502.37 mg g-1), respectively. The primary adsorption mechanisms for CIP and SPA included π-π electron donor-acceptor interaction, H-bonding, hydrophobic interaction and electrostatic interaction. Overall, the surface morphology and structural composition of biochars could be regulated with GO to facilitate the adsorption capacity. Moreover, the developed mGOCP could be extended as a potential adsorbent for removal of other emerging organic pollutants in water.

Discrimination of the species and authenticity of Rhizoma Coptidis based on stable isotope and multielement fingerprinting and multivariate statistical analysis.

It is essential to be able to identify the source species and to determine the authenticity of traditional Chinese medicines (TCM) in order to prevent the use of false or inferior medicines. In this work, a stable and reliable method of discriminating among the three source species of Rhizoma Coptidis and checking the authenticity of Rhizoma Coptidis samples was established. The technique involved evaluating stable isotope ratios and the contents of multiple elements in samples along with the use of multivariate statistical techniques. The stable isotope ratios δ13C, δ15N, δ2H, and δ18O and the concentrations of various inorganic elements (Li, B, Na, Mg, Al, P, Si, K, Ca, Ti, Mn, Fe, Cu, Zn, Sr, and Ba) in authentic Rhizoma Coptidis samples from three source species (n = 56) and in counterfeit Rhizoma Coptidis samples (n = 39) were determined. The results showed that there were significant differences between the samples from different source species according to multivariate statistical analysis. The three species were clearly distinguished using hierarchical cluster analysis (HCA). Employing stepwise linear discriminant analysis (SLDA), a classification model for differentiating the three species was developed, and this model achieved 100% classification accuracy when applied to samples. In addition, authentic samples and counterfeit samples were successfully discriminated using stable isotope and multielement fingerprint analysis and orthogonal projections to latent structures discriminant analysis (OPLS-DA), and OPLS-DA models for checking the authenticity of Rhizoma Coptidis were established and verified. Therefore, stable isotope and multielement analysis combined with multivariate statistical analysis was shown to be a promising method of discriminating among the three source species of Rhizoma Coptidis and of establishing the authenticity of Rhizoma Coptidis samples. Graphical abstract.

A high efficient adsorbent for plant growth regulators based on ionic liquid and ß-cyclodextrin functionalized magnetic graphene oxide.

Four types of ionic liquids which composed of cation with imidazole ring and anion with benzene, naphthalene, anthraquinone and naphthoquinone ring were prepared and named VOIm+BenSO3-, VOIm+NapSO3-, VOIm+AQSO3- and VOIm+NQSO3-, respectively. Then, ionic liquids and ß-cyclodextrin functionalized magnetic graphene oxide materials were firstly synthesized for the extraction of 23 plant growth regulators in vegetable samples. The synthesized materials anticipated the unique properties of ionic liquids, ß-cyclodextrin, graphene oxide and Fe3O4@SiO2, including high surface area, high supramolecular recognition capability, superparamagnetism and large delocalized π-electron system, which were successfully characterized. Among four kinds of ionic liquids functionalized adsorbents, the VOIm+AQSO3- modified material exhibited high adsorption capability to 7 plant growth regulators compared with Fe3O4@SiO2/GO/ß-CD, Fe3O4@SiO2/GO and other three types of ionic liquids based adsorbents. Parameters that could affect the recoveries of 7 plant growth regulators were investigated, such as mass ratio of Fe3O4@SiO2/GO/ß-CD to ionic liquids, salt concentration, pH, amount of adsorbent, extraction time and desorption solvent. Under the optimal condition, the magnetic solid phase extraction method using VOIm+AQSO3- and ß-cyclodextrin functionalized magnetic graphene oxide material (Fe3O4@SiO2/GO/ß-CD/IL) as adsorbent was developed and coupled with ultra-high performance liquid chromatography-triple quadrupole linear ion trap mass spectrometry for the determination of 7 plant growth regulators in vegetable samples. Validation results showed that the limit of detection and limit of quantitation were in the range of 0.01-0.18 µg/kg and 0.03-0.58 µg/kg, respectively. The satisfactory linearities were acquired in the concentration of 2-50 µg/kg with the correlation coefficients higher than 0.9982. Taken together, the synthesized Fe3O4@SiO2/GO/ß-CD/IL was a highly effective magnetic solid phase extraction adsorbent for the enrichment of trace level of plant growth regulators in vegetable samples.

Controllable synthesis of magnetic nanoporous carbon with tunable porosity for the efficient cleanup of vegetable samples.

Highly graphitic nanoporous carbon (NPC) was obtained from an agricultural waste-citrus peel at optimum condition. Then, a low-cost and pore size-controlled magnetic graphitic nanoporous carbon (MNPC) with ultrahigh specific surface area (1064 m2 g-1) was successfully fabricated by coprecipitation of Fe3O4 particles onto NPC. The prepared MNPC was characterized by Brunauer-Emmett-Teller (BET), Raman spectrum, scanning electron microscope (SEM) and Fourier transform infrared spectrometry (FT-IR). BET results showed a significant increase in the micropores volume and specific surface area of MNPCs following the increase of carbonization temperature, which implied that highly efficient carbonization made NPC an excellent active phase for MNPC. Besides, the adsorption mechanism was investigated and turned out that π-π interactions between interfering substances and MNPC were considered to be the major driving force for the adsorption process. The experimental parameters affecting the cleanup efficiency was optimized through Response surface methodology (RSM) in detail. Under the optimal cleanup condition, the MNPC was applied for determination of 16 insecticides in vegetables coupled with gas chromatography-mass spectrometry (GC-MS), a satisfactory performance was obtained. Good linearity was observed in the investigated concentration range of 1-100 µg kg-1 with correlation coefficients (r2) between 0.9963 and 0.9999. The limits of detection (LODs) were in the range of 0.03-0.33 µg kg-1. The recoveries ranged from 81.9 to 112.3% with relative standard deviations (RSDs) less than 10.9%. To summary up, the MNPC could potentially be used as a super adsorbent to efficiently remove pigments from vegetables, so that the proposed method was an efficient cleanup and enrichment procedure.

Cost-efficient magnetic nanoporous carbon derived from citrus peel for the selective adsorption of seven insecticides.

A magnetic solid-phase extraction adsorbent that consisted of citrus peel-derived nanoporous carbon and silica-coated Fe3 O4 microspheres (C/SiO2 @Fe3 O4 ) was successfully fabricated by co-precipitation. As a modifier for magnetic microspheres, citrus peel-derived nanoporous carbon was not only economical and renewable for its raw material, but exerted enormous nanosized pore structure, which could directly influence the type of adsorbed analytes. The C/SiO2 @Fe3 O4 also possessed the advantages of Fe3 O4 microspheres like superparamagnetism, which could be easily separated magnetically after adsorption. Integrating the superior of biomass-derived nanoporous carbon and Fe3 O4 microspheres, the as-prepared C/SiO2 @Fe3 O4 showed high extraction efficiency for target analytes. The obtained material was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and the Brunauer-Emmett-Teller method, which demonstrated that C/SiO2 @Fe3 O4 was successfully synthesized. Under the optimal conditions, the adsorbent was selected for the selective adsorption of seven insecticides before gas chromatography with mass spectrometry detection, and good linearity was obtained in the concentration range of 2-200 µg/kg with the correlation coefficient ranging from 0.9952 to 0.9997. The limits of detection were in the range of 0.03-0.39 µg/kg. The proposed method has been successfully applied to the enrichment and detection of seven insecticides in real vegetable samples.

Fabrication of a high selectivity magnetic solid phase extraction adsorbent based on ß-cyclodextrin and application for recognition of plant growth regulators.

An adsorbent, consisting of silica-coated Fe3O4 grafted graphene oxide and ß-cyclodextrin (Fe3O4@SiO2/GO/ß-CD), which possessed the merits of antioxidation, superparamagnetism, high surface area, high supramolecular recognition and environment friendly, was successfully fabricated. Considering the synergy between ß-CD and graphene oxide in adsorption mechanism, the synthesized adsorbent could grasp compounds especially with aromatic structures through π-π interaction, hydrophobic interaction and host-guest inclusion complex forming. Based on the advantages, a magnetic solid phase extraction (MSPE) method for 9 PGRs using Fe3O4@SiO2/GO/ß-CD as adsorbents was developed in this study. The characterizations of Fe3O4@SiO2/GO/ß-CD were performed on Fourier transform infrared spectrometry (FT-IR), X-ray photoelectron spectroscopy (XPS), CHNS/O elemental analyzer, scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). Under the optimal MSPE condition, the Fe3O4@SiO2/GO/ß-CD exhibited selectivity capability toward 9 PGRs when compared with Fe3O4@SiO2/GO. Meanwhile, the selectivity capability of Fe3O4@SiO2/GO/ß-CD was higher than that of Fe3O4@SiO2/GO/α-CD except for 4-FPA. When the developed MSPE procedure was coupled with ultra-high performance liquid chromatography-triple quadrupole linear ion trap mass spectrometry (UHPLC-QTrap-MS/MS) to quantitative analysis of 9 PGRs, linearities ranging from 2 to 50 µg/kg were achieved for 9 PGRs with the correlation coefficients (r2) in the range of 0.9975-0.9999. The limits of detection (LODs) for 9 analytes varied from 0.04 to 0.29 µg/kg. Finally, the proposed technique was applied to analyze PGRs residues in mutiple vegetable samples.

A novel magnetic ß-cyclodextrin modified graphene oxide adsorbent with high recognition capability for 5 plant growth regulators.

ß-Cyclodextrin (ß-CD) modified magnetic graphene oxide material (Fe3O4@SiO2/GO/ß-CD), a novel magnetic sorbent for enrichment and purification of plant growth regulators (PGRs) in vegetables prior to gas chromatograph mass spectrometer (GC-MS) detection, was successfully fabricated. The novel magnetic sorbent geometrically fitted to selectively recognize and enrich PGR analytes especially containing aromatic structure. The selectivity experiment demonstrated the higher selectivity of Fe3O4@SiO2/GO/ß-CD toward 5 PGR compounds than that of Fe3O4@SiO2/GO. Several parameters affecting extraction efficiency including the volume of extraction solvent, amount of adsorbent, extraction time, type and the volume of desorption solvent were optimized. Under the optimized condition, good linear relationships were obtained in the range of 1-100µg/kg with determination coefficients (R2) from 0.9983 to 0.9996. The limits of detection (LODs) of 5 PGRs were from 0.04 to 0.28µg/kg. The proposed method had good potential for the analysis of trace level of 5 PGRs in real vegetable samples.