Facile and tunable fabrication of Fe3O4/graphene oxide nanocomposites and their application in the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons from environmental water samples

Magnetic solid-phase extraction of caffeine from surface water samples with a micro–meso porous activated carbon/Fe3O4 nanocomposite prior to its determination by GC-MS

A novel micro–meso porous activated carbon/Fe₃O₄ (Bm) composite was synthesized from the active charcoal precursor BAX-1500 and used in the magnetic solid-phase extraction (MSPE) of caffeine prior to its determination by gas chromatography-mass spectrometry (GC-MS). The main factors affecting the extraction and desorption steps of the MSPE procedure were investigated and optimized. These factors include extraction time, sorbent mass and salt addition for the adsorption step and type of eluent, desorption time and volume of desorption solution for the desorption step. Under optimum conditions, the absolute extraction recovery was found to be 91.1% and good linearity was observed in the investigated concentration range of 0.6–12.5 ng mL⁻¹ (R² = 0.9997). The limit of detection was 0.18 ng mL⁻¹ and the limit of quantification was 0.60 ng mL⁻¹. The method was successfully applied to the analysis of surface water samples. The proposed MSPE method is simple, rapid, sensitive and environmentally friendly.

A novel magnetic solid phase material based on a micro–meso porous activated carbon/Fe₃O₄ nanocomposite was used to extract caffeine from surface water samples. The method is efficient and rapid, and has minimum solvent consumption.

Applications of surface functionalized Fe3O4 NPs-based detection methods in food safety

Food safety has always been an issue of great concern to people. The development of rapid, sensitive and specific detection technology of food pollutants is one of the hot issues in food science field. The rapid development of functionalized Fe₃O₄ nanoparticles (NPs) provides unprecedented opportunities and technical support for the innovation of food safety detection. The surface functionalized Fe₃O₄ NPs, which combine superparamagnetic with nanoscale feature, have become an excellent tool for food quality and safety detection. This review highlights the mechanism, principles, and applications of surface functionalized Fe₃O₄ NPs-based detection technique in the agrifood industry. Then the relevant characteristics, functional roles and general mechanisms of nanomaterial-based detection of various endogenous components and exogenous pollutants in foods are discussed in detail. Ultimately, this review is expected to promote the optimization of functionalized Fe₃O₄ NPs and provide direction for the diversity of signal recognition and the sustainability of detection methods.

Self-Assembled Three-Dimensional Microporous rGO/PNT/Fe3O4 Hydrogel Sorbent for Magnetic Preconcentration of Multi-Residue Insecticides

The purpose of this work was to develop a highly selective, sensitive, and reliable method for multi-residual analysis. A three-dimensional microporous reduced graphene oxide/polypyrrole nanotube/magnetite hydrogel (3D-rGOPFH) composite was synthesized and utilized as a magnetic solid-phase extraction (MSPE) sorbent to preconcentrate thirteen insecticides, including five organophosphorus (isocarbophos, quinalphos, phorate, chlorpyrifos, and phosalone), two carbamates (pirimor and carbaryl), two triazoles (myclobutanil and diniconazole), two pyrethroids (lambda-cyhalothrin and bifenthrin), and two organochlorines (2, 4′-DDT and mirex), from vegetables, followed by gas chromatography-tandem mass spectrometry. This method exhibited several major advantages, including simultaneous enrichment of different types of insecticides, no matrix effect, high sensitivity, and ease of operation. This is ascribed to the beneficial effects of 3D-rGOPFH, including the large specific surface (237 m2 g−1), multiple adsorption interactions (hydrogen bonding, electrostatic, π–π stacking and hydrophobic interaction force), appropriate pore size distribution (1–10 nm), and the good paramagnetic property. Under the optimal conditions, the analytical figures of merit were obtained as: linear dynamic range of 0.1–100 ng g−1 with determination coefficients of 0.9975–0.9998; limit of detections of 0.006–0.03 ng g−1; and the intra-day and inter-day relative standard deviations were 2.8–7.1% and 3.5–8.8%, respectively. Recoveries were within the range of 79.2 to 109.4% for tomato, cucumber, and pakchoi samples at the fortification levels of 5, 25, and 50 ng g−1. This effective and robust method can be applied for determining multi-classes of insecticide residues in vegetables.

Novel materials for dispersive (micro) solid-phase extraction of polycyclic aromatic hydrocarbons in environmental water samples: A review

Polycyclic aromatic hydrocarbons are hazardous environmental pollutants that possess mutagenic and carcinogenic properties. Generally, the concentrations of PAHs in environmental water samples are very low, and it is challenging to detect such levels directly by the analytical instrumentation. Thus, the extraction of PAHs using suitable extraction methodology is required for sample cleanup and analyte enrichment. Dispersive solid-phase extraction has several advantages over conventional approaches for the extraction of PAHs from environmental water samples. In this article, we critically evaluate the role of different nano and micro sorbent materials employed in the extraction of PAHs. Carbon-based nanomaterials, metal-organic frameworks, polymeric nanocomposites, ionic-liquid based composites, and silica-based materials are explicitly covered. This review also provides insight on functional components of all types of sorbents and their way of interaction with PAHs. The factors affecting the dispersive (micro) solid phase extraction of PAHs such as the design of the sorbent, the ratio of functional material to magnetic core, sample volume, amount of sorbent, extraction and desorption times, desorption solvent and its volume, salt addition, and sample pH are critically appraised. Finally, a brief account on the accomplishments, limitations, and challenges associated with such methods is provided.

Magnetic Cu: CuO-GO nanocomposite for efficient dispersive micro-solid phase extraction of polycyclic aromatic hydrocarbons from vegetable, fruit, and environmental water samples by liquid chromatographic determination

In this research, we presented a magnetic dispersive micro-solid phase extraction (MD-μ-SPE) method coupled with high performance liquid chromatography (HPLC) based on the use of magnetic Cu: CuO-Graphene Oxide (GO) nanocomposite (Fe₃O₄/Cu: CuO/GO-NC) for the separation and preconcentration of polycyclic aromatic hydrocarbons (PAHs), i.e. naphthalene (Nap), phenanthrene (Phe), anthracene (Ant), and pyrene (Pyr), in vegetable (onion, tomato, carrot, herb, watermelon, lettuce, eggplant, and chili pepper), fruit (apple, watermelon, and grape), wastewater, and water samples. The MD-μ-SPE of PAHs in matrix samples was carried out, and the impacts of pH, ionic strength, extraction time, temperature, eluent volume, and sorbent mass on the recovery of PAHs were investigated by using Placket-Burman design (PBD). In addition, by using the central composite design (CCD), the best combination of each important variable was measured. Sorbent mass of 14 mg, eluent volume of 200 μL, and 12 min extraction time at the central level of other factors were optimal conditions of pretreatment for the highest extraction recovery (ER%) of trace PAHs. Under the optimal conditions, the method proposed herein provided high enrichment factors ranged from 116.51 to 133.05, good linearity in the range of 10-3800 ng mL^-1 for Pyr, 3.0-3500 ng mL^-1 for Phe, 5.0-3200 ng mL^-1 for Nap, and 5.0-3000 ng mL^-1 for Ant with coefficient of determination (R²) values between 0.9889 and 0.9963, low limits of detection (LOD) and quantification (LOQ) in the range of 0.015-0.061 and 0.485-2.034 ng mL^-1, respectively, and also satisfactory spiked recoveries (between 95.1% and 106.8%) with the relative standard deviations (RSDs) values in the range of 1.73%-5.62%. The Fe₃O₄/Cu: CuO/GO-NC-based MD-μ-SPE followed by HPLC-UV corroborated promising results for the convenient and effective determination of PAHs in the samples of vegetables, fruits, and environmental water. The results of this study revealed that our developed method is easy, feasible, precise, highly effective, and convenient to operate for the trace analysis of PAHs in different real samples. The extraction recovery was about 90% of the initial recovery after the sorbent usage for three times; therefore, the Fe₃O₄/Cu: CuO/GO-NC can readily be regenerated.

Sample Preparation Using Graphene-Oxide-Derived Nanomaterials for the Extraction of Metals

Graphene oxide is a compound with a form similar to graphene, composed of carbon atoms in a sp2 single-atom layer of a hybrid connection. Due to its significant surface area and its good mechanical and thermal stability, graphene oxide has a plethora of applications in various scientific fields including heterogenous catalysis, gas storage, environmental remediation, etc. In analytical chemistry, graphene oxide has been successfully employed for the extraction and preconcentration of organic compounds, metal ions, and proteins. Since graphene oxide sheets are negatively charged in aqueous solutions, the material and its derivatives are ideal sorbents to bind with metal ions. To date, various graphene oxide nanocomposites have been successfully synthesized and evaluated for the extraction and preconcentration of metal ions from biological, environmental, agricultural, and food samples. In this review article, we aim to discuss the application of graphene oxide and functionalized graphene oxide nanocomposites for the extraction of metal ions prior to their determination via an instrumental analytical technique. Applications of ionic liquids and deep eutectic solvents for the modification of graphene oxide and its functionalized derivatives are also discussed.

Recent Advances in the Extraction of Polycyclic Aromatic Hydrocarbons from Environmental Samples

Polycyclic aromatic hydrocarbons (PAHs) comprise a group of chemical compounds consisting of two or more fused benzene rings. PAHs exhibit hydrophobicity and low water solubility, while some of their members are toxic substances resistant to degradation. Due to their low levels in environmental matrices, a preconcentration step is usually required for their determination. Nowadays, there is a wide variety of sample preparation techniques, including micro-extraction techniques (e.g., solid-phase microextraction and liquid phase microextraction) and miniaturized extraction techniques (e.g., dispersive solid-phase extraction, magnetic solid-phase extraction, stir bar sorptive extraction, fabric phase sorptive extraction etc.). Compared to the conventional sample preparation techniques, these novel techniques show some benefits, including reduced organic solvent consumption, while they are time and cost efficient. A plethora of adsorbents, such as metal-organic frameworks, carbon-based materials and molecularly imprinted polymers, have been successfully coupled with a wide variety of extraction techniques. This review focuses on the recent advances in the extraction techniques of PAHs from environmental matrices, utilizing novel sample preparation approaches and adsorbents.

Electrostatic self-assembly of pFe3O4 nanoparticles on graphene oxide: A co-dispersed nanosystem reinforces PLLA scaffolds

Cell responses and mechanical properties are vital for scaffold in bone regeneration. Fe₃O₄ nanoparticles with excellent magnetism can provide magnetic stimulation for cell growth, while graphene oxide (GO) nanosheets are commonly used as reinforcement phases due to their high strength. However, Fe₃O₄ or GO is tended to agglomerate in matrix. In present study, a novel co-dispersed Fe₃O₄-GO nanosystem was constructed through electrostatic self-assembly of positively charged Fe₃O₄ (pFe₃O₄) on negatively charged GO nanosheets. In the nanosystem, pFe₃O₄ nanoparticles and GO nanosheets support each other, which effectively alleviates the π-π stacking between GO nanosheets and magnetic attraction between pFe₃O₄ nanoparticles. Subsequently, the nanosystem was incorporated into poly _L-lactic acid (PLLA) scaffolds fabricated using selective laser sintering. The results confirmed that the pFe₃O₄-GO nanosystem exhibited a synergistic enhancement effect on stimulating cell responses by integrating the capturing effect of GO and the magnetic simulation effect of pFe₃O₄. The activity, proliferation and differentiation of cells grown on scaffolds were significantly enhanced. Moreover, the nanosystem also exhibited a synergistic enhancement effect on mechanical properties of scaffolds, since the pFe₃O₄ loaded on GO improved the efficiency of stress transfer in matrix. The tensile stress and compressive strength of scaffolds were increased by 67.1% and 132%, respectively. In addition, the nanosystem improved the degradation capability and hydrophilicity of scaffolds.

Critical review of micro-extraction techniques used in the determination of polycyclic aromatic hydrocarbons in biological, environmental and food samples

Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous environmental contaminants and their accurate determination is very important to human health and environment safety. In this review, sorptive-based micro-extraction techniques [such as Solid-Phase Micro-extraction (SPME), Stir Bar Sorptive Extraction (SBSE), Micro-extraction in Packed Sorbent (MEPS)] and solvent-based micro-extraction [Membrane-Mediated Liquid-Phase Micro-extraction (MM-LPME), Dispersive Liquid-Liquid Micro-extraction (DLLME), and Single Drop Micro-extraction (SDME)] developed for quantification of PAHs in environmental, biological and food samples are reviewed. Moreover, recent micro-extraction techniques that have been coupled with other sample extraction strategies are also briefly discussed. The main objectives of these micro-extraction techniques are to perform extraction, pre-concentration and clean up together as one step, and the reduction of the analysis time, cost and solvent following the green chemistry guidelines.

Polyamine-Modified Magnetic Graphene Oxide Nanocomposites and HPLC-MS/MS Allow the Determination of Two Indolic Derivatives in Strong-Aroma Types of Base Baijiu

Simultaneous detection of 3-indoleacetic acid (IAA) and 3-indolepropionic acid (IPA) in strong-aroma types of base Baijiu (base SAB) is crucial for elucidating the metabolic pathway of 3-methylindole during the base SAB brewing. Herein, a novel magnetic poly(allylamine)-modified graphene oxide (GO@PAA@Fe₃O₄) was synthesized as extraction sorbent, followed by high performance liquid chromatography mass spectrometry HPLC-MS/MS. As a surface modifier of GO, the introduction of PAA and Fe₃O₄ provided more adsorption sites for IAA and IPA, mainly through the generation of H-bonding sites. Moreover, modified by an activation step, the capacity of the activated GO@PAA@Fe₃O₄ for the adsorption of IAA and IPA was 2.1-3.4 times higher than that of unactivated material. The adsorptions of IAA and IPA on GO@PAA@Fe₃O₄ were fitted to the pseudo-second-order kinetic model and Langmuir isotherm, respectively. Under the optimal conditions, IAA and IPA were determined in 16-base SAB for the first time, and their concentrations ranged from 0.6 to 11.3 and 0.7 to 18.7 μg/L, respectively.

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 Solid-Phase Extraction of Organic Compounds Based on Graphene Oxide Nanocomposites

Graphene oxide (GO) is a chemical compound with a form similar to graphene that consists of one-atom-thick two-dimensional layers of sp²-bonded carbon. Graphene oxide exhibits high hydrophilicity and dispersibility. Thus, it is difficult to be separated from aqueous solutions. Therefore, functionalization with magnetic nanoparticles is performed in order to prepare a magnetic GO nanocomposite that combines the sufficient adsorption capacity of graphene oxide and the convenience of magnetic separation. Moreover, the magnetic material can be further functionalized with different groups to prevent aggregation and extends its potential application. Until today, a plethora of magnetic GO hybrid materials have been synthesized and successfully employed for the magnetic solid-phase extraction of organic compounds from environmental, agricultural, biological, and food samples. The developed GO nanocomposites exhibit satisfactory stability in aqueous solutions, as well as sufficient surface area. Thus, they are considered as an alternative to conventional sorbents by enriching the analytical toolbox for the analysis of trace organic compounds.

Can contaminated waters or wastewater be alternative sources for technology-critical elements? The case of removal and recovery of lanthanides

Technology critical elements (TCE) are considered the vitamins of nowadays technology. Factors such as high demand, limited sources and geopolitical pressures, mining exploitation and its negative impact, point these elements as new emerging contaminants and highlight the importance for removal and recycling TCE from contaminated waters. This paper reports the synthesis, characterization and application of hybrid nanostructures to remove and recover lanthanides from water, promoting the recycling of these high value elements. The nanocomposite combines the interesting properties of graphite nanoplatelets, with the magnetic properties of magnetite, and exhibits good sorption properties towards La(III), Eu(III) and Tb(III). The sorption process was very sensitive to solution pH, evidencing that electrostatic interactions are the main binding mechanism involved. Removal efficiencies up to 80% were achieved at pH 8, using only 50 mg/L of nanocomposite. In ternary solution, occurred a preferential removal of Eu(III) and Tb(III). The equilibrium evidenced a rare but interesting behaviour, and as a proof-of-concept the recoveries and reutilization rates, at consecutive cycles, highlight the recyclability of the composite without loss of efficiency. This study evidences that surface charge and the number of active sites of the composite controls the removal process, providing new insights on the interactions between lanthanoids and magnetic-graphite-nanoplatelets.

Adsorption Behavior of Polycyclic Aromatic Hydrocarbons on Zn-Based Coordination Cluster Zn5: Competition, Synergy, and Mechanism

In this work, adsorption behaviors of pyrene (PYR), fluoranthene (FLT), phenanthrene (PHE), and fluorene (FLU) on the coordination cluster [Zn₅(H₂Lⁿ)₆](NO₃)₄]·8H₂O·2CH₃OH (Zn₅) were studied. The adsorption mechanism and spectrum analyses revealed that the synergistic effect of hydrophobic interaction, π-π stacking, and N-H···π interaction played a crucial role during the adsorption process. The maximum adsorption capacities of PYR, FLT, PHE, and FLU were 406.4, 399.7, 153.7, and 114.3 mg g^-1, respectively, resulting from the Langmuir isotherm model. Quick removal of PYR and FLT was found in kinetic experiments with the adsorption equilibrium being reached within 1 min. Competitive adsorption indicated that the adsorption sites for PYR, FLT, PHE, and FLU on Zn₅ were identical, and synergistic effects also existed in the adsorption process. Therefore, Zn₅ has the potential to be used as an adsorbent in the field of wastewater treatment.

Green synthesis of magnetic carbon nanodot/graphene oxide hybrid material (Fe3O4@C-nanodot@GO) for magnetic solid phase extraction of ibuprofen in human blood samples prior to HPLC-DAD determination

In this study, a green production method was used to obtain magnetic carbon nanodot/graphene oxide hybrid material (Fe₃O₄@C-nanodot@GO) for the magnetic solid phase extraction (MSPE) of ibuprofen (IBU) in human plasma prior to HPLC-DAD determination. For the first time in the literature, Fe₃O₄@C-nanodot@GO hybrid material was synthesized and used as an adsorbent. C-nanodots were produced from pasteurized cow milk by using a simple and cheap hydrothermal method. After production of the C-nanodots and GO, Fe₃O₄@C-nanodot@GO hybrid material was fabricated in green solvent medium by using an one-step hydrothermal method. The method was based on the simple separation, preconcentration and analysis of ibuprofen by using MSPE-HPLC-DAD combination. The concentration changes of ibuprofen in human bloods against time were successfully monitored by using this combined method. For this purpose, blood samples were taken from volunteers at certain intervals after the administration of a certain dose of ibuprofen, and the MSPE method was used to monitor the concentration changes of ibuprofen in the blood samples. Experimental variables affecting the extraction efficiency of IBU such as sample solution pH, amount of adsorbent, extraction time, eluent type and volume were studied and optimized in the details. The characterization studies for the Fe₃O₄@C-nanodot@GO were carried out by X-ray diffraction spectrometry (XRD), Fourier transform infrared spectrometry (FT-IR), Raman spectrometry (Raman), energy dispersive x-ray (EDX), vibrating sample magnetometry (VSM) and scanning electron microscopy (SEM) techniques. Under the optimum experimental conditions, the limit of detection (LOD) was 8.0 ng mL^-1 and the recoveries at three spiked levels in human plasma were ranged from 91.0% to 95.0% with the relative standard deviation (RSD %) less than 4.0 % (n = 6). The results show that together use of MSPE with HPLC-DAD provides a simple and rapid analysis of ibuprofen in human plasma samples.

Remediation of PAHs contaminated soil using a sequence of soil washing with biosurfactant produced by Pseudomonas aeruginosa strain PF2 and electrokinetic oxidation of desorbed solution, effect of electrode modification with Fe3O4 nanoparticles

This work aimed to investigate the performance of biosurfactant, produced by a halotolerant bacterial strain, Pseudomonas aeruginosa PF2, for desorption of PAHs from soil, followed by electrokinetic oxidation of the desorbed solution using Magnetite Nanoparticles Modified Graphite (MNMG). Pyrene (PYR), anthracene (ANT) and phenanthrene (PHE) were used as contamination model. Produced and extracted biosurfactant was characterized as rhamnolipid with Critical Micelle Concentration (CMC) of 60 mg/L and emulsification index (E₂₄) value of 60.2% for n-hexadecane, 58.4% for n-heptane and 55.6% for n-Hexane, respectively. Results of LC-MS/MS analysis indicated the presence of seven major peaks at m/z of 677.5, 531.1, 649.3, 528.9, 475.1, 359 and 503.2, which corresponded to the deprotonated molecules of RhaRhaC₁₂C_10, RhaC₁₂C_10, RhaRhaC₁₀C₁₀, RhaC_12:1C_10, RhaC₈C_10, Rha-C₁₂:₂ and RhaC₁₀C_10, respectively. The maximum desorption of PAHs was derived at pH value of 6, CMC of 3 and contact time of 24 h. Modification of graphite electrode enhanced the PAH degradation significantly. In electrokinetic oxidation of desorbed solution, the best results were observed at pH value of 5, contact time of 6 h, voltage of 3 V and electrolyte concentration of 25 mg/L, with the average removal efficiency of higher than 99% for all studied PAHs.

Graphene oxide-Fe3O4 nanocomposite magnetic solid phase extraction followed by UHPLC-MS/MS for highly sensitive determination of eight psychoactive drugs in urine samples

Graphene oxide-Fe₃O₄ (GO-Fe₃O₄) nanocomposite was synthesized by a facile chemical co-precipitation method. The GO-Fe₃O₄ was used as magnetic sorbent to extract the eight psychoactive drugs from urine samples. The analytes are morphine (MOR), 6-monoacetylmorphine (6-MAM), amphetamine (AMP), methamphetamine (MAMP), codeine, cocaine, dolantin and benzoylecgonine (BZE), which were determined by ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). This method has high selectivity for the target analytes. The limit of detection (LOD) and limit of quantification (LOQ) were 0.02-0.2 μg L^-1 and 0.05-0.5 μg L^-1, respectively. The Mandel's fitting test revealed good linearity within all linear ranges. The linear ranges were calculated as 0.05-1000 μg L^-1 for AMP, MAMP, cocaine and dolantin; 0.1-1000 μg L^-1 for 6-MAM and codein; and 0.5-1000 μg L^-1 for MOR and BZE. The recoveries ranged in 80.4-105.5%. The intra-day and inter-day RSDs are in the range of 2.7-13.1% and 3.9-13.7%, respectively. Magnetic solid phase extraction (MSPE) with GO-Fe₃O₄ provides a convenient, rapid and green sample pretreatment method for extracting the target psychoactive drugs from urine. This methodology can be used for simultaneous or individual detection of eight major psychoactive drugs with high sensitivity. This method has high potential in clinical and forensic areas for psychoactive drugs analysis.

One-step synthesized magnetic MIL-101(Cr) for effective extraction of triazine herbicides from rice prior to determination by liquid chromatography-tandem mass spectrometry

The magnetic metal-organic framework MIL-101(Cr) material-based solid-phase extraction method coupled with high-performance liquid chromatography and tandem mass spectrometry was applied to extract seven triazine herbicides in rices. Fe₃ O₄ /MIL-101(Cr) was synthesized using reduction-precipitation method, in which steps including pre-synthesis and modification of Fe₃ O₄ nanoparticles were by-passed. Various parameters including extraction solvent type and volume, ultrasonic extraction time, amount of Fe₃ O₄ /MIL-101(Cr) microspheres, adsorption time, desorption volume and time were investigated. Under optimal conditions, the proposed method had the limit of detection (S/N = 3) and the limit of quantification (S/N = 10) of 1.08-18.10 and 3.60-60.20 pg/g, respectively. Relative standard deviations calculated for all herbicides with concentrations of 2 and 20 ng/g were in the range of 0.5 to 13% (n = 3). In addition, at the two above-mentioned concentrations, the method achieved relative recoveries percentages of 79.3 to 116.7% when applied to determine the triazine herbicides in real samples spiked. This rapid, green, non-polluting, pre-concentrated extraction method was successfully developed and applied to analyze herbicides in rice samples.

Coated direct inlet probe coupled with atmospheric-pressure chemical ionization and high-resolution mass spectrometry for fast quantitation of target analytes

The coated direct inlet probe (CDIP) is a new laboratory-made low-cost technology developed from a direct inlet probe (DIP), which has the advantage of quick enrichment/cleanup of an analyte from liquid samples. A capillary probe is coated with hydroxy-terminated polydimethylsiloxane (OH-PDMS), divinylbenzene (DVB), and β-cyclodextrin (β-CD) by a sol-gel method. This probe can be directly coupled with a commercialized atmospheric-pressure chemical ionization (APCI) ion source and high-resolution mass spectrometry, which are widely applicable, reliable, and durable. The ability to perform quantitative analyses with the use of a stable-isotope-labeled internal standard (SIL-IS) was tested by using different concentrations of acenaphthylene (ACY), acenaphthene (ACP), fluorene (FLR), fluoranthene (FLT), phenanthrene (PHE), and benzo[a]pyrene (B[a]P). Calibration curves with a coefficient of determination of R² ≥ 0.9982 for different polycyclic aromatic hydrocarbons (PAHs) were obtained. A limit of detection (LOD) of 0.008-0.04 ng mL^-1 for PAHs was determined. The entire workflow is solvent-free and can be completed in less than 5 min, which demonstrates the advantages of this technique for quantitative analysis.

Developed nano carbon-based coating for simultaneous extraction of potent central nervous system stimulants from urine media by stir bar sorptive extraction method coupled to high performance liquid chromatography

A nano graphene oxide sol-gel composite (NGO/sol-gel) applied as a coating of a capillary glass tube stir bar to develop a novel stir bar sorptive extraction (SBSE) method for simultaneous extraction of amphetamine (AMP) and methamphetamine (MET) from biological urine sample. Lab-synthesized NGO was applied with methyltrimethoxysilane (MTMOS) and Tetraethoxysilane (TEOS) as sol-gel precursor. NGO/sol-gel was deposited on the surface of a capillary glass tube to prepare stir bar sorptive extraction adsorbent by a simple and fast method. The scanning electron micrograph images showed a three dimensional structure of lab-made device suitable for SBSE method for simultaneous extraction of AMP and MET. Effective extraction parameters were investigated. Through studied suitable extraction conditions, satisfactory linearity was achieved in the concentration range of 50-2000 ngmL^-1 for AMP and 40-2500 ngmL^-1 for MET. The relative recovery of the analytes were 99.5 and 99.7% for AMP and MET, respectively for positive urine samples were studied by novel introduced method. The results cleared that NGO/sol-gel composite could be used as practical method in laboratories as an efficient SBSE adsorbent for drugs determination in urine matrix.

Preparation and characterization of magnetic nanomaterial and its application for removal of polycyclic aromatic hydrocarbons

Fe₃O₄@polyaniline, a Fe₃O₄-based magnetic core-shell material, was synthesized and its morphology and microstructure were characterized with transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometry. Polyaniline was modified onto the surface of Fe₃O₄ nanoparticles by a self-assembly method based on a two-step oxidative polymerization method. The new materials exhibited good adsorption to polycyclic aromatic hydrocarbons such as fluoranthene, pyrene and benzo[a]pyrene from environmental water samples due to the high affinities of polyaromatic hydrocarbons to polyaniline via π-π and van der Waals interactions. The experimental results indicate that the adsorption of polyaromatic hydrocarbons follows pseudo-second order kinetics and the adsorption isotherms conform to a Langmuir isotherm model. The thermodynamic parameters for polyaromatic hydrocarbons indicate that the adsorption process is spontaneous and endothermic in nature, but adsorption occurs via non-covalent interactions. This study indicated that the Fe₃O₄@polyaniline hybrid core-shell structure was proved to be a good adsorbent for polyaromatic hydrocarbons while exhibiting simple preparation, easy separation, low cost, high reusability and great potential applicability for removal of polyaromatic hydrocarbons from water.