Magnetic nanocomposite as sorbent for magnetic solid phase extraction coupled with high performance liquid chromatography for determination of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons in water environments: Impact, legislation, depollution processes and challenges, and magnetic iron oxide/graphene-based nanocomposites as promising adsorbent solutions

Environmental pollution is a big challenge of today's world, as population continues to grow, and industrialisation and urbanisation increase. Out of the different micropollutants in the atmosphere and aquatic environments, polycyclic aromatic hydrocarbons are of particular importance because they have known severe associated health risks to human life and they have high stability, leading to their persistence in the environment. They are generally present in the environment in low concentrations, but, even at these levels, they pose threats. This review thus focuses on this family of pollutants, on their occurrence and consequences, as well as the current methodologies employed to remove them from water environments and the challenges that remain. This work then focuses on the potential of magnetic iron oxide/graphene nanocomposites for the adsorption of PAHs, extensively discussing past and undergoing works, as well as the interactions between these adsorbents and PAHs.

Development of Fe3O4/DEX/PDA@Au(Raman reporters)@Au-MPBA nanocomposites based multi-hotspot SERS probe for ultrasensitive, reliable, and quantitative detection of glucose in sweat

Glucose is a key biomarker of diabetes, and effective glucose monitoring methods are crucial to the prevention and management of diabetes. Therefore, in this paper, Fe3O4/DEX/PDA@Au (Raman reporters) @Au nanocomposites were synthetized that with DTNB (5,5'-dithiobis(2-nitrobenzoic)), MMTA (2-mercapto-4-methyl-5-thiazole acetic acid), MBA (4-mercaptobenzoic acid) and 4-Mpy(4-Mercaptopyridine) were used separately as Raman reporters. Fe3O4 and PDA (Polymerized dopamine) could supply more high surface area of active sites and high SERS (Surface-Enhanced Raman Scattering) substrate, which has high stability and reproducibility. Dextran coating is an effective way to prepare biocompatible materials TEM, XRD, TG and VSM were used to analyze the size, morphology and magnetic properties of the nanocomposites. Fe3O4/DEX/PDA@Au(Raman reporters)@Au that integrates a multi-hotspot structure and magnetic separation techniques were studied the enhancement effect of Raman spectra, and glucose solutions with different concentrations were tested. Furthermore, the optimal Fe3O4/DEX/PDA@Au(Raman reporters)@Au nanocomposites were supplied as SERS substrates for detection of glucose accurately and quickly in sweat. SERS signal intensity is linearly correlated with glucose concentration within the measurement range of 5 × 10-3 to 10 mM, and the minimum detectable concentration is 5 µM. The Fe3O4/DEX/PDA@Au(Raman reporters)@Au nanocomposites exhibit high reliability, specificity and repeatability of the strategy were then verified by practical detection of sweat.

Employing a magnetic chitosan/molybdenum disulfide nanocomposite for efficiently removing polycyclic aromatic hydrocarbons from milk samples

This study aimed to develop a highly efficient nanocomposite composed of magnetic chitosan/molybdenum disulfide (CS/MoS2/Fe3O4) for the removal of three polycyclic aromatic hydrocarbons (PAHs)-pyrene, anthracene, and phenanthrene. Novelty was introduced through the innovative synthesis procedure and the utilization of magnetic properties for enhanced adsorption capabilities. Additionally, the greenness of chitosan as a sorbent component was emphasized, highlighting its biodegradability and low environmental impact compared to traditional sorbents. Factors influencing PAH adsorption, such as nanocomposite dosage, initial PAH concentration, pH, and contact time, were systematically investigated and optimized. The results revealed that optimal removal efficiencies were attained at an initial PAH concentration of 150 mg/L, a sorbent dose of 0.045 g, pH 6.0, and a contact time of 150 min. The pseudo-second-order kinetic model exhibited superior fitting to the experimental data, indicating an equilibrium time of approximately 150 min. Moreover, the equilibrium adsorption process followed the Freundlich isotherm model, with kf and n values exceeding 7.91 mg/g and 1.20, respectively. Remarkably, the maximum absorption capacities for phenanthrene, anthracene, and pyrene on the sorbent were determined as 217 mg/g, 204 mg/g, and 222 mg/g, respectively. These findings underscore the significant potential of the CS/MoS2/Fe3O4 nanocomposite for efficiently removing PAHs from milk and other dairy products, thereby contributing to improved food safety and public health.

Surfactant-enhanced air-agitation liquid-liquid microextraction of polycyclic aromatic hydrocarbons from edible oil using magnetic deep eutectic solvent prior to HPLC determination

Herein, an air-agitation liquid-liquid microextraction procedure was developed for the extraction of several polycyclic aromatic hydrocarbons from edible oil samples. In this study, the extraction procedure was achieved using a new magnetic deep eutectic solvent as the extraction solvent, in which there was no need for centrifugation. To enhance the rate of extraction of the analytes from the samples, the method was promoted by the use of surfactant addition. The extracted analytes were determined by high-performance liquid chromatography with a diode array detector. The influence of various parameters on the extraction efficiency was studied by response surface methodology using a central composite design. Under optimal conditions, linear calibration curves for the target analytes were achieved in the range of 0.43-250 ng g-1. The limits of detection and quantification were in the ranges of 0.04-0.13 and 0.13-0.43 ng g-1, respectively. The repeatability of the method in terms of intra- and inter-day precision was ≤4.7% and ≤6.7%, respectively. The extraction recovery of the method ranged from 75 to 88%. The obtained results show that the proposed method is efficient for the analysis of the target analytes in various oil samples without obvious matrix effects. Pyrene was found in olive oil at a concentration of 42 ng g-1.

Preparation of Novel Solid Phase Extraction Sorbents for Polycyclic Aromatic Hydrocarbons (PAHs) in Aqueous Media

In this study, functionalized mesoporous silica was prepared and characterized as a stationary phase using various analytical and solid-state techniques, including a Fourier-transform infrared (FTIR) spectrometer, thermogravimetric analysis, and nitrogen sorption. The results confirmed the successful synthesis of the hybrid stationary phase. The potential of the prepared hybrid mesoporous silica as a solid-phase extraction (SPE) stationary phase for separating and enriching polycyclic aromatic hydrocarbons (PAHs) in both spiked water samples and real water samples was evaluated. The analysis involved extracting the PAHs from the water samples using solid-phase extraction and analyzing the extracts using a two-dimensional gas chromatograph coupled to a time-of-flight mass spectrometer (GC × GC-TOFMS). The synthesized sorbent exhibited outstanding performance in extracting PAHs from both spiked water samples and real water samples. In the spiked water samples, the recoveries of the PAHs ranged from 79.87% to 95.67%, with relative standard deviations (RSDs) ranging from 1.85% to 8.83%. The limits of detection (LOD) for the PAHs were in the range of 0.03 µg/L to 0.04 µg/L, while the limits of quantification (LOQ) ranged from 0.05 µg/L to 3.14 µg/L. Furthermore, all the calibration curves showed linearity, with correlation coefficients (r) above 0.98. Additionally, the results from real water samples indicated that the levels of individual PAH detected ranged from 0.57 to 12.31 µg/L with a total of 44.67 µg/L. These findings demonstrate the effectiveness of the hybrid mesoporous silica as a promising stationary phase for solid-phase extraction and sensitive detection of PAHs in water samples.

The green synthesis of magnesium oxide nanocomposite-based solid phase for the extraction of arsenic, cadmium, and lead from drinking water

Solid-phase extraction (SPE) has attracted the attention of scientists because it can increase the selectivity and sensitivity measurements of analytes. Therefore, this study is designed to synthesise magnesium oxide nanoparticles (D-MgO-NPs) by an eco-friendly method using biogenic sources Duranta erecta followed by fabricating its chitosan-based polymeric composite (D-MgO-NC) for the SPE of heavy metals (HMs), i.e., arsenic (As), cadmium (Cd), and lead (Pb) from drinking water. Various analytical techniques were used for the surface characterization of D-MgO-NPs and D-MgO-NC. FTIR findings confirmed the formation of D-MgO-NC based on MgO association with the -OH/-NH2 of the chitosan. D-MgO-NC showed the smallest size of particles with rough surface morphology, followed by the crystalline cubic structure of MgO in its nanoparticle and composites. The synthesised D-MgO-NC was used as an adsorbent for the SPE of HMs from contaminated water, followed by their detection by atomic absorption spectrometry. Various experimental parameters, including pH, flow rate, the concentration of HMs, eluent composition, and volume, were optimised for the preconcentration of HMs. The limits of detection for As, Cd, and Pb of the proposed D-MgO-NC-based SPE method were found to be 0.008, 0.006, and 0.012 μm L-1, respectively. The proposed method has an enrichment factor and relative standard deviation of >200 and <5.0%, respectively. The synthesised D-MgO-NC-based SPE method was successfully applied for the quantitative detection of As, Cd, and Pb in groundwater samples, which were found in the range of 18.3 to 15.2, 3.20 to 2.49, and 8.20 to 6.40 μg L-1, respectively.

Determination of trace bisphenols in milk based on Fe3O4@NH2-MIL-88(Fe)@TpPa magnetic solid-phase extraction coupled with HPLC

Herein, a covalent organic framework (COF) was grown on a magnetic metal-organic framework (MOF) by a solvothermal method for the efficient extraction of bisphenols (BPs). The magnetic solid-phase extraction (MSPE) of four bisphenols (bisphenol A, bisphenol B, bisphenol AF and bisphenol C) was carried out without adjusting the pH and salt concentration. When 30 mg Fe₃O₄@NH₂-MIL-88(Fe)@TpPa was used to adsorb for 25 min, 6 mL methanol was used to elute for 20 min, and the extract was detected by high-performance liquid chromatography (HPLC). The proposed method has a low detection limit of 0.011-0.036 ng mL^-1, a wide linear range of 0.05-100 ng mL^-1, and a correlation coefficient (R²) of 0.9980-0.9998. The intra-day and inter-day precisions are 0.74-2.54% and 1.68-3.72%, respectively. Bisphenol A was determined by applying the proposed method to the determination of actual milk samples. The standard addition experiment showed that the relative recovery of the four bisphenols was 85.70-119.7%. Pseudosecond-order, first-order, Langmuir and Freundlich models were applied to explore the adsorption characteristics of Fe₃O₄@NH₂-MIL-88(Fe)@TpPa. In general, the established Fe₃O₄@NH₂-MIL-88(Fe)@TpPa-MSPE-HPLC-UV method exhibits attractive sensitivity, simple manipulation, and excellent reusability, and it has excellent prospects for the detection of trace BPs in complex milk matrices.

Deep eutectic solvent-based iron nanoparticles coated by N, S-doped amorphous carbon and its application in magnetic Dµ-SPE combined with DLLME for the extraction of PAHs in eyeliner

This work presents a preparation of new magnetic nanoparticles coated with amorphous carbon and their application in dispersive solid-phase extraction in simultaneous extraction of sixteen polycyclic aromatic hydrocarbons from eyeliner. The extraction procedure was hyphenated with a lower density than water dispersive liquid-liquid microextraction (DLLME) for further preconcentration of the analytes to sensitive determination of them with gas chromatography-flame ionization detection. The magnetic adsorbent was prepared sonically from iron pentacarbonyl and then the nanoparticles were coated by N, S-doped amorphous carbon and the deep eutectic solvent prepared from tetrabutyl ammonium chloride and decanoic acid. The magnetic properties of the nanoparticles were studied by vibrating sample magnetometer. Also, scanning electron microscopy was used to investigate the nanoparticles morphology. The extraction procedure was done by migration of the analytes from eyeliner into a proper aqueous solution and their adsorption onto the nanoparticles. Then, the analytes were eluted and more concentrated by the DLLME approach. After validating the method, acceptable limit of detection and broad linear range were accessed in the ranges of 0.25-0.54 and 1.8-250 ng/g, respectively. Relative standard deviation values were ≤ 7.1% for the repeated analyses in the same day (n = 6) and different days (n = 6). Extraction recovery of the method was in the range of 79-96%. The introduced method was successfully used for the analysis of the PAHs in five eyeliner samples and only two of them were identified in all samples at ng/g level.

Determination of pyrethroids in water samples by dispersive solid-phase extraction coupled with high-performance liquid chromatography

A metal-organic framework UiO-66 was prepared and used as a sorbent for dispersive solid-phase extraction combined with high-performance liquid chromatography (DSPE-HPLC) for extracting and determining four pyrethroids in water samples for the first time. The as-synthesized material was confirmed by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and N₂ adsorption-desorption analysis. In addition, several important parameters affecting DSPE efficiency, including sorbent dosage, extraction time, salt concentration, pH, elution solvent, elution volume, and elution time, were optimized. Under the optimum conditions, the UiO-66 based on the DSPE-HPLC method displayed a wide linear range (10-1000 ng/ml), low limits of detection (2.8-3.5 ng/ml), and good precision (relative standard deviations [RSDs] < 3%) for the four pyrethroids. The recoveries at different spiked levels ranged from 89.3% to 107.7%. In addition, UiO-66 featured good reusability and reproducibility. The results demonstrated that π-π stacking interactions, hydrophobic interactions, and van der Waals forces between UiO-66 and the four pyrethroids played a crucial role in the adsorption process. Meanwhile, the maximum extraction capability could be obtained within 5 min. Thus, the DSPE coupled with the UiO-66 sorbent can be successfully used in the analysis of four pyrethroids in environmental water samples. PRACTITIONER POINTS: Simultaneous determination of four pyrethroids using the developed UiO-66-based DSPE-HPLC method in water samples. The developed method had a short enrichment time, broad linear ranges, a low detection limit, and high enrichment factor. It is showed that π-π stacking interaction, hydrophobic interaction, and van der Waals forces were the main mechanism.

Research Progress of Polycyclic Aromatic Hydrocarbons Pretreatment Methods and Application of Computer Simulation Technology for Prediction and Degradation of Electrochemical Concentration Detection

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds that are composed of aromatic rings containing only carbon and hydrogen atoms. They are one of the widespread environmental pollutants in the world. In recent years, many scholars have focused on the inhibition, formation mechanism, content of active components, and biodegradation effect of polycyclic aromatic hydrocarbons. They summarized the research progress of pretreatment methods for detection, but rarely discussed the experimental dataset for comprehensive analysis of pollution sources and the impact of different pretreatment technologies on the extraction of different substrates. What is more, computer simulation has not been mentioned. In this study, the pollution sources of polycyclic aromatic hydrocarbons (PAHs) are reviewed, and the related applications of various pretreatment methods such as gel permeation chromatography (GPC) are summarized. Finally, the computer simulation of the response surface method is introduced. The concentration of polycyclic aromatic hydrocarbons is tested or predicted by combining the neural network with the alternating trilinear decomposition (ATLD) algorithm, artificial population algorithm (ABC), and hierarchical genetic algorithm (HGA). Its future development trend is discussed and prospected, which provides a reference for solving the pollution problem. We look forward to providing help for the follow-up research of scholars in this field.

Application of curcumin as a green and new sorbent in deep eutectic solvent-based dispersive micro-solid phase extraction of several polycyclic aromatic hydrocarbons from honey samples prior to gas chromatography-mass spectrometry determination

A green, simple, and efficient dispersive micro-solid phase extraction method was developed for the extraction of polycyclic aromatic hydrocarbons from honey samples. In this method, for the first time, curcumin was used as an efficient and green sorbent to extract the analytes from the sample. After that the adsorbed analytes were eluted using a deep eutectic solvent prepared by mixing tetrabutylammonium chloride: ethylene glycol and analyzed by gas chromatography-mass spectrometry. Important experimental factors affecting adsorption and desorption steps of the method were optimized and under optimal experimental conditions, low limits of detection (0.14-0.37 ng/g) and quantification (0.49-1.3 ng/g), wide linear range (1.3-500 ng/g) with a coefficient of determination ≥0.994 were obtained. Relative standard deviation values for intra- and interday precisions were ≤7.5% for all of the analytes at a concentration of 2 ng/g for each analyte (n = 6). Extraction recovery of the method was in the range of 72-81%. Finally, 20 honey samples were analyzed and the analytes were successfully detected. The method is environment friendly because of the use of curcumin as a sorbent. Also, biodegradability of the used deep eutectic solvent components is another advantage of the method.

Recent advances and applications of cyclodextrins in magnetic solid phase extraction

Cyclodextrins (CDs) as a family of cyclic oligosaccharides are toroidal with a hydrophobic interior and a hydrophilic exterior. They are well-known for their ability to form host-guest inclusion complexes with different compounds. They are used as chiral stationary phases in high performance liquid chromatography (HPLC) and gas chromatography (GC) or as chiral reagents in the background electrolyte of capillary electrophoresis (CE). In recent years, they have been used for modification of sorbents or as sorbents in solid phase extraction (SPE) procedures. Magnetic solid-phase extraction (MSPE), as a new type of SPE procedure, has received considerable attention due to its rapid phase separation process as compared to traditional extraction mode. This review covers the synthesis of CD-based magnetic sorbents (such as immobilization of CDs onto the different supports, production of nanosponges, and making hybrid substances with nanomaterials) and the use of these compounds in MSPE of different analytes from biological, environmental, and food samples. Also, prospects of CD-based sorbents for sample pre-treatment are also proposed.

Nanoplatform-Integrated Miniaturized Solid-Phase Extraction Techniques: A Critical Review

Preparation of the biological samples is one of the most critical steps in sample analysis. In past decades, the liquid-liquid extraction technique has been used to extract the desired analytes from complex biological matrices. However, solid-phase extraction (SPE) gained popularity due to versatility, simplicity, selectivity, reproducibility, high sample recovery %, solvent economy, and time-saving nature. The superior extraction efficiency of SPE can be attributed to the development of advanced techniques, including the nanosorbents technology. The nanosorbent technology significantly simplified the sample preparation, improved the selectivity, diversified the application, and accelerated the sample analysis. This review critically expands on the to-date advancements reported in SPE with particular regards to the nanosorbent technology.

A thin-layer solid-phase extraction-liquid film elution technique used for the enrichment of polycyclic aromatic hydrocarbons in water

In this article, we propose a novel microsolid-phase extraction and elution technique, which we called the thin-layer solid-phase extraction-liquid film elution technique. The thin-layer solid-phase extraction phase is an octadecylsilylated sol gel- coated porous silica thin film prepared on the outer wall of a test tube, which has a larger surface area for the extraction of the target compounds compared to a conventional solid-phase microextraction phase. After optimization of the extraction procedure for five types of polycyclic aromatic hydrocarbons, the liquid film elution technique was investigated. Liquid film elution is an elution technique wherein the compounds extracted into the thin-layer solid-phase extraction phase are eluted using a small volume of solvent film formed around the extraction phase. The results show that the elution can be carried out using 150 μL of eluent. Enrichment factors between 20 and 34 were obtained for polycyclic aromatic hydrocarbons containing more than four aromatic rings in 10 mL aliquots of aqueous samples. Finally, recoveries of 85-112% were obtained for polycyclic aromatic hydrocarbons containing more than four aromatic rings from spiked natural water samples using the thin-layer solid-phase extraction-liquid film elution technique.

Magnetic solid phase extraction of heterocyclic aromatic hydrocarbons from environmental water samples with multiwalled carbon nanotube modified magnetic polyamido-amine dendrimers prior to gas chromatography-triple quadrupole mass spectrometer

Present study described a sensitive and efficient method for determination of heterocyclic aromatic hydrocarbons using multiwalled carbon nanotubes modified magnetic polyamido-amine dendrimers (MNPs@PAMAM-Gn@MWCNTs) as adsorbent for magnetic solid-phase extraction (MSPE) coupled with gas chromatography-triple quadrupole mass spectrometer (GC-MS/MS). Some pivotal parameters including PAMAM generation, adsorbent dosage, adsorption time, elution time and volume, pH and humic acid concentration were investigated to achieve the best adsorption efficiencies. Under the optimal conditions, 7-methylquinoline, dibenzothiophene and carbazole had good linearity in the concentration range of 0.005-20 μg L ^- 1, 9-methylcarbazole, 4-methyldibenzothiophene and 4,6-dimethyl dibenzothiophene had good linearity in the concentration range of 0.001-20 μg L ^- 1. All the correlation coefficients were higher than 0.996. The detection limits of the targets were in the range of 2.2 × 10^-4-1.8 × 10^-3 μg L ^- 1 with precisions less than 8.28% (n = 6). The enrichment factors were in the range of 141-147. The spiked recoveries were in the range of 87.0%-115.1% (n = 3). These results indicated that the method could be a reliable alternative tool for monitoring trace heterocyclic aromatic hydrocarbons in environmental water samples.

Highly efficient porous sorbent derived from asphalt for the solid-phase extraction of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are generated primarily during the incomplete combustion of organic matter and are ubiquitous environmental pollutants. For the first time, in this study, a mesoporous carbon derived from asphalt with high surface area (2300 m²g^-1 with an average of 1.2 cm³ g^-1) was utilized as a sorbent for the solid-phase extraction (SPE) of several PAHs in tap water samples. The factors influencing the extraction capability of the new material were investigated and the optimum conditions were determined to be as follows: Sample volume - 200 mL, no adjustment of sample pH, and sorbent amount - 50 mg. Under the most favorable SPE conditions, with gas chromatography-mass spectrometric analysis, the method exhibited a linear range of 0.5-50 μgL^-1 with limits of detection between 0.004 and 0.026 μgL^-1. The recoveries obtained from spiked tap water samples spiked at 1 μgL^-1 and 5 μgL^-1, were in the range 86.7-98.2% with relative standard deviations of <9%. The method was also applied to tap water samples collected from the local environment. The concentrations of PAHs detected ranged between 0.13 and 48 μgL^-1. The reusability of the sorbent was tested with five consecutive SPE extraction, and no carryover of analytes was observed.

Magnetic C60 nanospheres based solid-phase extraction coupled with isotope dilution gas chromatography-mass spectrometry method for the determination of sixteen polycyclic aromatic hydrocarbons in Chinese herbal medicines

C₆₀-based magnetic nanospheres were synthesized by coating Fe₃O₄ nanospheres with silica, then modifying with 3-aminopropyltriethoxysilane as a linker and a C₆₀ fullerene stationary phase. The morphologies, magnetic properties, infrared absorption and carbon content of magnetic nanospheres were studied by TEM, VSM, FTIR and carbon and sulfur analyzer. The magnetic nanospheres were employed for the magnetic solid-phase extraction (MSPE) of 16 polycyclic aromatic hydrocarbons (PAHs) in nine Chinese herbal medicines. The analyses were conducted by isotope dilution gas chromatography-mass spectrometry. The main parameters influencing the extraction, including extraction solvent, adsorbent amount, and extraction time were optimized. Method validation showed that the limit of detection (LOD) was 0.02-0.11 µg/kg, and the limit of quantification (LOQ) was 0.07-0.36 µg/kg. The spiked recoveries rates for 16 PAHs in white peony root were 84.7-107.2%. The relative standard deviation (RSD) was 1.7-8.4%. The established method was further used for the determination 16 PAHs in nine Chinese herbal medicines. Total content of 16 PAHs varied from 73.6 µg/kg (fructus lycii) to 2172.6 µg/kg (astragalus root). The results indicate that the pollution of PAHs in Chinese herbal medicines is serious. The established method can effective detect PAHs contamination in Chinese herbal medicines.

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.

Simultaneous enrichment and determination of cadmium and mercury ions using magnetic PAMAM dendrimers as the adsorbents for magnetic solid phase extraction coupled with high performance liquid chromatography

In present study, a sensitive and efficient method based on magnetic PAMAM dendrimers as the sorbents for magnetic solid-phase extraction (MSPE) coupled with high performance liquid-phase chromatography and ultraviolet variable wavelength detector (HPLC-VWD) was developed for simultaneous determination of trace cadmium and mercury ions. Sodium diethyldithiocarbamate (DDTC-Na) was used as the chelating agent during the elution process. Parameters that would affect the extraction efficiency including PAMAM generation, adsorbent dosage, adsorption time, elution time and volume, pH and coexisting ions were investigated to achieve the best adsorption efficiency. Under the optimal conditions, good linear relationship was obtained in the range of 0.05-200 μg L^-1 for Cd²⁺ and 0.1-200 μg L^-1 for Hg²⁺, and the limits of detection were 0.016 and 0.040 μg L^-1, respectively. The spiked recoveries of Cd²⁺ and Hg²⁺ were satisfied in the range of 91.5-105% (n = 3). The proposed method was proved to be an alternative and reliable method to determine trace Cd²⁺ and Hg²⁺ in water samples.

White bean (Phaseolus vulgaris L.) as a sorbent for the removal of zinc from rainwater

The present work aimed to assess the sorption capacity of the common white bean (Phaseolus vulgaris L.) to remove Zn(II) from rainwater, rendering it suitable for use in buildings, and the efficiency of the process was evaluated for two initial Zn(II) concentrations, representing high (100 μg L^-1) and very high (500 μg L^-1) levels of Zn(II) in rainwater. The effects of the amount of beans (1, 5 and 10 beans per 50 mL), as well as the initial pH values of the zinc solution [acid (4), neutral (5.6) and basic (7) for atmospheric waters] were also assessed. The removal of Zn from water was affected by the change in pH values. When 5 and 10 beans were used, after 4 h and 2 h of contact time, respectively, the accumulated Zn(II) on the beans was released back into the solution, and this release occurred first for the highest tested pH value. The sorption rate of Zn(II) from the solution increased with the increasing amount of beans, but for 5 and 10 beans this only took place up to 4 h and 2 h, respectively. Furthermore, the removal percentages of Zn(II) increased with the increase of the initial concentrations of the metal in water. Kinetic studies revealed that a pseudo-first-order model provided the best fitting for the experimentally obtained values. Fourier transform infrared spectroscopy coupled with attenuated total reflectance (FTIR-ATR) analyses of the bean shells and cores indicated that contact with a Zn(II) solution did not cause notable alterations to the chemical structures of these bean components. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analyses suggested that the process of sorption occurred at the surface of the beans (shells). The results obtained in this study also suggest that the matrix of rainwater samples did not interfere with the removal of metal, and that the process of the removal of Zn(II) by the white beans can be applied to real samples. On the whole, results indicate that for the removal of Zn(II) from rainwater, 1 bean up to 6 h, or 5 and 10 beans up to 2 h can be used per 50 mL for the removal of up to 60% of Zn(II) present in water, thus constituting a viable solution for the effective reduction of this metal in rainwater.

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.

Dispersive micro-solid phase extraction based on Fe3O4@SiO2@Ti-MOF as a magnetic nanocomposite sorbent for the trace analysis of caffeic acid in the medical extracts of plants and water samples prior to HPLC-UV analysis

In this work, Fe₃O₄@SiO₂@Ti-MOF-NCs, as an efficient sorbent, have been synthesized in a laboratory and utilized for extracting CA in the medical extracts of plants and water samples before their analysis by HPLC.