Graphene oxide framework: An adsorbent for solid phase extraction of phenylurea herbicides from water and celery samples

In situ formation of solidified supramolecular solvent based dispersive liquid-liquid microextraction for the enrichment of phenylurea herbicides in water, fruit juice, and milk

A convenient, efficient, and green dispersive liquid-liquid microextraction based on the in situ formation of solidified supramolecular solvents combined with high performance liquid chromatography was developed for the determination of four phenylurea herbicides in liquid samples, including monuron, monolinuron, isoproturon, and chlortoluron. Herein, a novel supramolecular solvent was prepared by the in situ reaction of [P4448]Br and NH4PF6, which had the advantages of low melting point, high density, and good dispersibility. In addition, the microscopic morphology and physical properties of supramolecular solvent were characterized, and the extraction conditions were optimized. The results showed that the analytes had good linearity (R2 > 0.9998) within the linear range. The limits of detection and quantification for the four phenylurea herbicides were in the range of 0.13-0.19 μg L-1 and 0.45-0.65 μg L-1, respectively. The prepared supramolecular solvent is suitable for the efficient extraction of phenylurea herbicides in water, fruit juice, and milk.

Urea-based magnetic porous organic frameworks as novel adsorbent for the enrichment of phenylurea herbicides in foods

A novel urea-based magnetic porous organic frameworks Fe₃O₄@UPOFs (ETTA-PPDI) was synthesized by a simple polymerization reaction under mild conditions. The adsorbent displayed desirable adsorption performance for phenylurea herbicides (PUHs) with optimized adsorption time of only 4 min. The adsorption capacities of the adsorbent for PUHs ranged from 47.30 to 111.93 mg g^-1. A magnetic solid-phase extraction based on Fe₃O₄@UPOFs combined with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established for the efficient determination of six PUHs in food samples (wheat, edible oil and cucumber), with determination coefficient (R²) ≥ 0.9972. The LODs of the method were in the range of 0.003-0.07 μg kg^-1 and recoveries ranged from 82.00 to 112.53%. The relative standard deviations were lower than 6.7%. The newly prepared adsorbent displayed great application prospects for the efficient enrichment of trace phenylurea herbicides in complex food matrices.

Heterogeneous adsorbent based on CeZrO2 nanoparticles doped magnetic graphene oxide used for vortex assisted magnetic dispersive solid phase extraction of erythromycin in chicken

A simple, fast, and efficient method of vortex assisted magnetic dispersive solid phase extraction for separation and pre-concentration of erythromycin in chicken samples prior to high LC-UV determination has been developed. The novel heterogeneous CeZrO₂ nanoparticles doped magnetic graphene oxide, for use as an efficient nanosorbent, was synthetised and applied for the adsorption of erythromycin. The synthetised nanosorbent was characterised using both Fourier-transform infra-red (FT-IR) and energy dispersive X-Ray (EDX) spectroscopy together with field emission scanning electron microscopy-EDX. To obtain the best extraction condition and maximum extraction efficiency of erythromycin, the effect of important parameters including pH, amount of sorbent, vortexing time, ionic strength, sample volume, and desorption conditions were investigated. At optimum conditions, a linear range of 0.25-300 µg kg^-1, LOD (S/N = 3) of 0.079 µg kg^-1, and LOQ (S/N = 10) of 0.270 µg kg^-1 were obtained. The precision of the method was established as having an RSD (%) at 100 µg kg^-1 of erythromycin for seven replicates of 2.6% and 3.2% for the intra-day and the inter-day, respectively. Recoveries over 94.0% confirmed a high capability of the proposed method for separation and determination of erythromycin residues in chicken being one of the most important animal products.

Solvent-free mechanochemical preparation of graphene oxide-Fe3 O4 and its application in magnetic dispersive solid-phase extraction of illegal dyes in food samples

A simple, green, and efficient mechanochemical approach was developed herein to prepare tunable magnetic graphene oxide nanoparticles. The obtained nanoparticles were successfully used as adsorbents in a magnetic dispersive solid-phase extraction method to extract three cationic dyes (i.e., thioflavine T, auramine-O, and basic orange 2) found in food samples. Our proposed approach also utilized high-performance liquid chromatography with ultraviolet detection. Several key variables affecting the extraction recovery were investigated. These included the sample pH, amount of extractant, extraction time, sample volume, elution solvent type and volume, and the stability and reusability of the magnetic graphene oxide nanoparticles. Under optimized conditions, the calibration curve was linear at a concentration range of 0.005-1.0 μg/mL with a correlation coefficient of 0.9992-0.9996. Moreover, the limits of detection were determined at 0.97-1.35 μg/mL. The extraction mechanism was investigated via ultraviolet-visible spectrophotometry and zeta-potential analyses. The developed method was used to analyze the above-mentioned cationic dyes in bean products and yellow fish samples. Notably, satisfactory spiked recoveries ranging from 90.7 to 104.9% were achieved.

A core-shell structured magnetic covalent organic framework as a magnetic solid-phase extraction adsorbent for phenylurea herbicides

In this work, a core-shell structured magnetic covalent organic framework named as M-TpDAB was constructed with 3,3'-diaminobenzidine (DAB) and 1,3,5-triformylphloroglucinol (Tp) as building units. M-TpDAB was characterized by infrared spectroscopy, nitrogen adsorption-desorption isotherms, powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Using the M-TpDAB as adsorbent, a simple and highly effective method was proposed for preconcentrating phenylurea herbicides before high performance liquid-phase chromatography analysis. In the optimized conditions, a good linearity was achieved within the range of 0.15-100 ng mL^-1 for water sample, 1.0-100.0 ng mL^-1 for tea drink samples. The limits of detection for the analytes were 0.05-0.15 ng mL^-1 for water sample and 0.30-0.50 ng mL^-1 for drink samples. Satisfactory recoveries of spiked target compounds were in the range of 84.6%-105% for water sample and 80.3%-102% for tea drink samples. Finally, the M-TpDAB based method was successfully used to determine phenylurea herbicides in tea drinks and water samples, demonstrating a good alternative for analyzing trace level of phenylurea herbicides in water samples.

Development, validation, comparison, and implementation of a highly efficient and effective method using magnetic solid-phase extraction with hydrophilic-lipophilic-balanced materials for LC-MS/MS analysis of pesticides in seawater

To achieve multi-pesticides residue analysis in seawater, hydrophilic-lipophilic-balanced magnetic particles were designed and fabricated by swelling polymerization of divinyl benzene (DVB) and N-vinyl pyrrolidone (NVP) on the surface of Fe₃O₄@SiO₂ magnetic particles. The ratio of DVB to NVP was adjusted to achieve a proper balance in hydrophilicity and lipophilicity. The obtained magnetic particles were systematically characterized by TEM, SEM, FT-IR and vibrating sample magnetization. Based on the optimized magnetic nanoparticles, a sensitive magnetic solid-phase extraction method was developed for the simultaneous pre-concentration and determination of 96-pesticide residues from large-volume seawater samples prior to being detected by liquid chromatography-tandem mass spectrometry. Recoveries of pesticides in spiked seawater samples (0.001, 0.01, 0.1, 1.0 μg L^-1) ranged from 62% to 112% with RSDs less than 21%. The method limits of detection of 96 pesticides ranged from 0.13 to 0.42 ng L^-1, the method limits of quantification of 96 pesticides ranged from 1.0 to 10 ng L^-1. The method was successfully applied to pesticide residue analysis in water samples from Jiulong River Estuary of China, demonstrating the prospects of this technique as a potential method for the rapid determination of trace levels of multi-pesticide residues in seawater.

Magnetic-Dispersive Solid Phase Extraction Based on Graphene Oxide-Fe3O4 Nanocomposites Followed by High Performance Liquid Chromatography-Fluorescence for the Preconcentration and Determination of Terazosin Hydrochloride in Human Plasma

In the present study, a facile modified impregnation method was employed to synthesize superparamagnetic graphene oxide-Fe3O4 (GO-Fe3O4) nanocomposites. Based on the GO-Fe3O4 as adsorbent, a simple and fast magnetic-dispersive solid phase extraction followed by high performance liquid chromatography with fluorescence detection (M-dSPE-HPLC-FL) method was established and validated for the preconcentration and determination of terazosin hydrochloride (TRZ) in human plasma samples. The obtained nanomaterials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and vibrating sample magnetometry. Different parameters affecting the extraction efficiency, such as sample pH, amount of sorbent, extraction time, elution solvent and its volume and desorption time, were evaluated and optimized. The linearity of the proposed method was excellent over the range 0.3-50.0 ng mL-1 with an acceptable coefficient of determination (R2 = 0.9989). The limit of quantification and limit of detection were found to be 0.3 and 0.09 ng mL-1, respectively, and the preconcentration factor of 10 was achieved. Intra- and inter-day precision expressed as relative standard deviation (RSD %, n = 6) were between 2.2-3.8% and 4.7-6.4%, respectively. Accuracy, estimated by recovery assays, was 97.7-106.6% with RSD ≤ 5.2%. Ultimately, the applicability of the method was successfully confirmed by the extraction and determination of TRZ in human plasma samples.

Zirconium metal-organic framework assisted miniaturized solid phase extraction of phenylurea herbicides in natural products by ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry

The zirconium metal-organic framework (Zr-MOF) was used as a novel and effective adsorbent material for the enrichment of five phenylurea herbicides (fenuron, monuron, diuron, linuron and pencycuron) in natural products. The target analytes were determined by ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Some crucial experimental parameters, such as type of adsorbents, amount of adsorbent, type of eluent solvents and adsorption capacity were investigated and optimized. Under the optimum extraction conditions, the enrichment factors of fenuron, monuron, diuron, linuron and pencycuron were 90, 128, 148, 204 and 295 times, respectively. A good linearity was obtained in different concentration levels of target analytes with the determination coefficients (r²) larger than 0.993. In addition, the limits of detection varied from 0.05 to 0.36 ng/mL and the recoveries of the analytes were in the range of 85.19-99.13 %. The results demonstrated that the proposed miniaturized solid-phase extraction procedure coupled with Zr-MOF could become an effective tool to analyze phenylurea herbicides and would have the vast application prospect for the extraction of pesticide residue and more organic pollutants from Hawthorn, Dendrobii Officinalis Caulis and Salviae Miltiorrhizae Radix et Rhizoma samples.

Materials for Solid-Phase Extraction of Organic Compounds

This review provides an overview of the most recent developments involving materials for solid-phase extraction applied to determine organic contaminants. It mainly concerns polymer-based sorbents that include high-capacity, as well as selective sorbents, inorganic-based sorbents that include those prepared using sol-gel technology along with structured porous materials based on inorganic species, and carbon nanomaterials, such as graphene and carbon nanotubes. Different types of magnetic nanoparticles coated with these materials are also reviewed. Such materials, together with their main morphological and chemical features, are described, as are some representative examples of their application as solid-phase extraction materials to extract organic compounds from different types of samples, including environmental water, biological fluids, and food.

Applications of Graphene and Its Derivatives in Chemical Analysis

In this review, the applications of graphene and its derivatives in the chemical analysis have been described. The properties of graphene materials which are essential for their use in chemical and biochemical analysis are characterized. The materials are used in sensors and biosensors, in electrochemistry, in chromatography and in the sample preparation techniques. Chemical and electrochemical sensors containing graphene materials are useful devices for detecting some chemical and biochemical compounds. Chromatographic columns for HPLC with graphene containing stationary phases may be used for separation of polar and nonpolar components of some specific mixtures. Graphene materials could be successfully employed during sample preparation for analysis with SPE, magnetic SPE, and SPME techniques. HighlightsThe review of the applications of graphene (G) and its derivatives, graphene oxide (GO) and reduced graphene oxide (rGO), in chemical and biochemical analysis is proposed.The electron donor-acceptor and proton donor-acceptor interactions for the graphene based materials - analytes systems and their impact on the analysis results are discussed, particularly:    i) in electrochemistry,ii) in chromatography,iii) in modern sample preparation techniquesiv) in sensors of different types.The essence of the thermal stability and the nomenclature of the graphene based materials in their different applications in chemical systems of different classes was discussed (and suggested).The benefits of using SPME fibers with immobilized graphene materials have been presented in detail.

Organically interconnected graphene flakes: A flexible 3-D material with tunable electronic bandgap

The structural and electronic properties of molecularly pillared graphene sheets were explored by performing Density Functional based Tight Binding calculations. Several different architectures were generated by varying the density of the pillars, the chemical composition of the organic molecule acting as a pillar and the pillar distribution. Our results show that by changing the pillars density and distribution we can tune the band gap transforming graphene from metallic to semiconducting in a continuous way. In addition, the chemical composition of the pillars affects the band gap in a lesser extent by introducing additional states in the valence or the conduction band and can act as a fine band gap tuning. These unique electronic properties controlled by design, makes Mollecular Pillared Graphene an excellent material for flexible electronics.

A magnetic covalent aromatic polymer as an efficient and recyclable adsorbent for phenylurea herbicides

A magnetic covalent aromatic polymer (Fe₃O₄-NH₂-CAP) was synthesized by grinding a covalent aromatic polymer (CAP) and amino-functionalized magnetic nanoparticles (Fe₃O₄-NH₂ NPs). The CAP was prepared by a Friedel-Crafts reaction between biphenyl and 1,3,5-benzenetricarbonyl trichloride. The interaction in the Fe₃O₄-NH₂-CAP is based on hydrogen bond formation between the carbonyl groups in the CAP and the amino groups in the Fe₃O₄-NH₂ NPs. The adsorbent inherits the advantages of the CAP and also has the superior magnetic property of the Fe₃O₄ NPs. The adsorbent was applied to magnetic solid-phase extraction of six phenylurea herbicides (metoxuron, monuron, chlortoluron, isoproturon, monolinuron, buturon) from soil and water samples. Following elution with 600 μL methanol, the herbicides were quantified by HPLC. The calibration plots are linear in the 1.00-100 ng g^-1 herbicide concentration ranges in case of spiked soil samples, and in the 0.10-40 ng mL^-1 concentration range for spiked water samples. The limits of detection range from 0.3 to 0.5 ng g^-1 (soil) and from 0.01 to 0.03 ng mL^-1 (water), with relative standard deviations of <8.0% and < 6.9%, respectively. Graphical abstract Schematic presentation for the preparation of the magnetic covalent aromatic polymer (Fe₃O₄-NH₂-CAP) and of magnetic solid-phase extraction.

Removal of 2,4-D, glyphosate, trifluralin, and butachlor herbicides from water by polysulfone membranes mixed by graphene oxide/TiO2 nanocomposite: study of filtration and batch adsorption

PURPOSE

Degradation or decomposition of the chemical herbicides by natural reagents after using can lead to produce various types of harmful intermediates. Ultrafiltration by the mixed matrix membranes blended with the graphene oxide/TiO₂ can remove the residual herbicides from aqueous solution.

METHODS

Graphene oxide/TiO₂x% (x = 10, 30, 50%) was prepared by solvothermal method and blended by polysulfone to prepare GO/TiO₂/PSf membranes for dynamic rejection of aqueous solutions of glyphosate, 2,4-D, butachlor, and trifluralin in a dead-end flow system. The blended membranes were also applied for the adsorption of herbicides in batch experiments.

RESULTS

Addition of GO/TiO₂ nanocomposite increased water flux from 7.3 for pure membrane to 211-326 kg/m² h for mixed matrix samples in order to increase of the membrane porosity and surface hydrophilicity. The herbicides rejections were found in the range of 50-70% related to GO/TiO₂ content. It was found that the membrane blended with 0.5 wt.% of GO/TiO₂(10%) demonstrated the most efficiency.

CONCLUSIONS

Details of dynamic filtration showed that the blended membrane acted based on the size exclusion mechanism. Adsorption experiments indicated that the strong attractions between H-bond donor sites of the herbicide and GO/TiO₂ nanoparticles in membranes played a key role in the increase of adsorption of herbicides on the membrane.

Constructing a three-dimensional graphene structure via bonding layers by ion beam irradiation

In recent years, the use of the multilayer graphene sheets has been considered more than the single-layer due to the cost-effectiveness and the possibility of mass production. But this type of graphene has some kind of structural weakness due to the weak physical link between its layers. Then, in order to strengthen, many structural modifications are proposed by various techniques to manage the mechanisms at interlayer distances. In this study, the focused ion beam irradiation method has been examined to cross-link and strengthen multi-layer graphene sheets with the help of the molecular dynamics simulation technique. Then, uniaxial and transverse tensile tests were performed to check the mechanical properties of obtained cross-linked multilayer graphene sheets. The results of this research can be considered for the creation of a new class of graphene structures. Such structures could be implemented as a membrane in water desalination or as a storage foam in hydrogen or carbon dioxide storage.

Magnetic dispersive solid-phase extraction based on graphene oxide/Fe3 O4 @polythionine nanocomposite followed by atomic absorption spectrometry for zinc monitoring in water, flour, celery and egg

BACKGROUND

Magnetic graphene oxide nanocomposite has been proposed as a promising and sustainable sorbent for the extraction and separation of target analytes from food matrices. Sample preparation based on nanocomposite presents several advantages, such as desired efficiency, reasonable selectivity and high surface-area-to-volume ratio.

RESULTS

A new graphene oxide/Fe₃ O₄ @polythionine (GO/Fe₃ O₄ @PTh) nanocomposite sorbent was introduced for magnetic dispersive solid-phase extraction and flame atomic absorption spectrometric detection of zinc(II) in water, flour, celery and egg. To fabricate the sorbent, an oxidative polymerization of thionine on the surface of magnetic GO was applied, while polythionine was simply employed as a surface modifier to improve extraction yield. The properties of the sorbent were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis, vibrating sample magnetometry and Fourier transform-infrared spectroscopy. The calibration curve showed linearity in the range of 0.5-30 ng mL^-1 . Limits of detection (S/N = 3) and quantification (S/N = 10) were 0.08 and 0.5 ng mL^-1 , respectively.

CONCLUSION

The method was applied for trace-level determination of Zn(II) in water and food samples, and its validation was investigated by recovery experiments and analyzing certified reference material. © 2018 Society of Chemical Industry.

Facile synthesis of amine-functional reduced graphene oxides as modified quick, easy, cheap, effective, rugged and safe adsorbent for multi-pesticide residues analysis of tea

Amine-functional reduced graphene oxide (amine-rGO) with different carbon chain length amino groups were successfully synthesized. The graphene oxides (GO) reduction as well as amino grafting were achieved simultaneously in one step via a facile solvothermal synthetic strategy. The obtained materials were characterized by X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectrometry and X-ray photoelectron spectroscopy to confirm the modification of GO with different amino groups. The adsorption performance of catechins and caffeine from tea acetonitrile extracts on different amine functional rGO samples were evaluated. It was found that tributylamine-functional rGO (tri-BuA-rGO) exhibited the highest adsorption ability for catechins and caffeine compared to GO and other amino group functional rGO samples. It was worth to note that the adsorption capacity of catechins on tri-BuA-rGO was 11 times higher than that of GO (203.7mgg^-1 vs 18.7mgg^-1). Electrostatic interaction, π-π interaction and surface hydrophilic-hydrophobic properties of tri-BuA-rGO played important roles in the adsorption of catechins as well as caffeine. The gravimetric analysis confirmed that the tri-BuA-rGO achieved the highest efficient cleanup preformance compared with traditional dispersive solid phase extraction (dSPE) adsorbents like primary-secondary amine (PSA), graphitized carbon black (GCB) or C18. A multi-pesticides analysis method based on tri-BuA-rGO is validated on 33 representative pesticides in tea using gas chromatography coupled to tandem mass spectrometry or high-performance liquid chromatography coupled with tandem mass spectrometry. The analysis method gave a high coefficient of determination (r²>0.99) for each pesticide and satisfactory recoveries in a range of 72.1-120.5%. Our study demonstrated that amine functional rGO as a new type of QuEChERS adsorbent is expected to be widely applied for analysis of pesticides at trace levels.

Trace determination of chlorpheniramine in human plasma using magnetic dispersive solid-phase extraction based on a graphene oxide/Fe3O4@polythionine nanocomposite combined with high-performance liquid chromatography

Graphene oxide/Fe₃O₄@polythionine (GO/Fe₃O₄@PTh) nanocomposite was fabricated for magnetic dispersive solid-phase extraction and high-performance liquid chromatography-ultraviolent detection (HPLC) of chlorpheniramine in human plasma.