Fabrication and evaluation of magnetic activated carbon as adsorbent for ultrasonic assisted magnetic solid phase dispersive extraction of bisphenol A from milk prior to high performance liquid chromatographic analysis with ultraviolet detection

Assessing dietary bisphenol A exposure among Koreans: comprehensive database construction and analysis using the Korea National Health and Nutrition Examination Survey

Bisphenol A (BPA) exposure primarily occurs through dietary intake. This study aimed to estimate the extent of dietary BPA exposure among Koreans. A thorough literature search was conducted to establish a BPA content database encompassing common foods consumed in Korea, including various food raw materials and processed food products. Dietary exposure levels were estimated by integrating the constructed BPA database with comprehensive nationwide 24 h-dietary recall datasets. The finding revealed that dietary BPA exposure was low for most Koreans, with a mean of 14.5 ng/kg bw/day, but was higher for preschool-age children (over 23 ng). Canned foods accounted for 9-36% of the total dietary exposure of the highest dietary exposure groups; while across all age groups, a considerable amount was derived from canned tuna, contribution of canned fruits and canned coffee (milk-containing) was high for preschool-age children and adults, respectively. Notably, for adults, a substantial proportion also stemmed from beer packaged in cans. While diet contributed over 80% of aggregate exposure for most age groups, preschool-age children experienced 60% exposure through diet due to additional exposure from indoor dust. Even at the high exposure scenario, aggregate BPA exposure levels remained lower than the current tolerable daily intake (TDI) set by the Korean agency (20 μg/kg bw/day). Nevertheless, most Koreans were exposed to BPA levels surpassing the strictest TDI (0.2 ng/kg bw/day) set by the European Food Safety Authority.

Magnetic activated carbon as an adsorbent for extraction of DMMP from aqueous samples followed by GC-IMS analysis

Micro-porous magnetic activated carbon was prepared under ultrasonic irradiation as an adsorbent for dispersed solid phase extraction of dimethyl methyl phosphonate from water samples, before analysis by gas chromatography-ion mobility spectrometry. The magnetic activated carbon was synthesized and characterized by using a vibrating sample magnetometer, Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction techniques. Then, the effects of the amount of sorbent, extraction time and pH of the sample in the dispersive solid phase extraction method were investigated and optimized by the response surface method. The dispersion of 20 mg adsorbent powder in a 50 mL water sample for 5 minutes with chloroform as the desorption solvent showed an average recovery value of 95% for dimethyl methyl phosphonate. Afterward, the method was used successfully for the determination of dimethyl methyl phosphonate in river and spring water. The linear range was obtained to be 0.05-1 μg mL-1. The limit of detection and the limit of quantification were obtained to be 0.02 μg mL-1 and 0.05 μg mL-1 respectively. The analysis also showed good reproducibility with a relative standard deviation value of 3.1%. This method was shown to be easy, fast, reliable, and inexpensive.

Extensive sorption of Amoxicillin by highly efficient carbon-based adsorbent from palm kernel: Artificial neural network modeling

In the present study, a new sorbent was fabricated from Palm kernel (PK) by dry thermochemical activation with NaOH and characterized by FTIR, X-ray diffraction, FE-SEM and BET, which was used for the Amoxicillin (AMX) sorption from aqueous solution. The influence of effective parameters such as pH, reaction time, adsorbent dosage, AMX concentration and ionic strength on the sorption efficacy of AMX removal were evaluated. The main functional groups on the surface of the magnetic activated carbon of Palm Kernel (MA-PK) were C-C, C-O, C[bond, double bond]O and hydroxyl groups. The specific surface of char, activated carbon Palm Kernel (AC-PK) and MA-PK were 4.3, 1648.8 and 1852.4 m2/g, respectively. The highest sorption of AMX (400 mg/L) was obtained by using 1 g/L of sorbent at solution pH of 5 after 60 min contact time, which corresponding to 98.77%. Non-linear and linear models of isotherms and kinetics models were studied. The data fitted well with Hill isotherm (R2 = 0.987) and calculated maximum sorption capacity were 719.07 and 512.27 mg/g from Hill and Langmuir, respectively. A study of kinetics shows that the adsorption of AMX follows the Elovich model with R2 = 0.9998. Based on the artificial neural network (ANN) modeling, the MA-PK dosage and contact time showed the most important parameters in the removal of AMX with relative importance of 36.5 and 25.7%, respectively. Lastly, the fabricated MA-PK was successfully used to remove the AMX from hospital wastewater.

Sensitive determination of bisphenols in environmental samples by magnetic porous carbon solid-phase extraction combined with capillary electrophoresis

Bisphenol compounds exist widely in the environment and pose potential hazards to the environment and human health, which has aroused widespread concern. Therefore, there is an urgent need for an efficient and sensitive analytical method to enrich and determine trace bisphenols in environmental samples. In this work, magnetic porous carbon (MPC) was synthesized by one-step pyrolysis combined with a solvothermal method for magnetic solid-phase extraction of bisphenols. The structural properties of MPC were characterized by field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and saturation magnetization analysis. Its adsorption properties were evaluated by adsorption kinetics and adsorption isotherm studies. By optimizing the magnetic solid-phase extraction and capillary electrophoresis separation conditions, a capillary electrophoresis separation and detection method for four bisphenols was successfully constructed. The results showed that the detection limits of the proposed method for the four bisphenols were 0.71-1.65 ng/mL, the intra-day and inter-day precisions were 2.27-4.03% and 2.93-4.42%, respectively, and the recoveries were 87.68%-108.0%. In addition, the MPC could be easily recycled and utilized, and even if the magnetic solid-phase extraction was repeated 5 times, the extraction efficiency could still be kept above 75%.

Solvent-assisted dispersive micro-solid phase extraction of bisphenols using iron(III) thenoyltrifluoroacetonate complex (Fe(TTA)3) as a new nanostructured sorbent: a proof of concept

In this work, we describe for the first time the use of iron(III) thenoyltrifluoroacetonate complex (Fe(TTA)₃) as a novel sorbent for solvent-assisted dispersive micro-solid phase extraction (SA-dμSPE) of bisphenols from water samples. The extraction procedure is based on the formation of nanoparticles in situ following the rapid injection of a methanolic solution of Fe(TTA)₃ into the stirred aqueous sample. Herein, the synthesis of Fe(TTA)₃ and study of the essential parameters of the preparative procedure are described. The optimized procedure allowed for efficient enrichment of bisphenols from various water samples, chosen as model contaminants and matrix, within 2.5 min. The sorbent was collected by centrifugation, dissolved in methanol, and injected to perform HPLC with spectrophotometric detection. The limits of detection and quantification obtained ranged from 1.0-3.1 and 3.1-7.5 μg L^-1, respectively. Intraday and interday precisions of <7% relative standard deviation (RSD) and <8% RSD with analyte recoveries ranging between 70-117% (103.8% on average) were obtained for the analysis of river water, wastewater treatment plant effluent, and bottled water.

Selective fluorescent probe for sensitive determination of bisphenol A based on molecularly imprinted polymers decorated carbon dots derived from citric acid and ethylenediamine

Bisphenol A (BPA) is an endocrine disrupting chemical and poses a grave threat to the human health. Herein, a fluorescent probe constructed with molecularly imprinted polymers decorated carbon dots (CDs@MIPs) was proposed for determination of BPA with high selectivity. The CDs@MIPs were constructed using BPA, 4-vinylpyridine and ethylene glycol dimethacrylate as template, functional monomer and cross linker, respectively. The obtained fluorescent probe not only owned a highly selective recognition function derived from MIPs but also displayed an excellent sensitivity for sensing BPA stemmed from CDs. The fluorescence intensity of CDs@MIPs was varied before and after the removal of BPA templates. The fluorescent decrease fraction of the fluorescent probe demonstrates a nice linearity in BPA concentration range of 10-2000 nM (r² = 0.9998) and the detection limit is as low as 1.5 nM. The fluorescent probe was triumphantly utilized to sense the level of BPA in real aqueous and plastic samples with good results. Moreover, the fluorescent probe offered a wonderful means for fast identification and sensitive detection of BPA from environmental aqueous samples.

Challenges in the Analytical Preparation of a Biological Matrix in Analyses of Endocrine-Disrupting Bisphenols

Endocrine-disrupting chemicals (EDCs) are xenobiotics presented in a variety of everyday products that may disrupt the normal activity of hormones. Exposure to bisphenol A as EDC at trace and ultra-trace levels is associated with adverse health effects, and children are recognized as the most vulnerable group to EDCs exposure. In this review, a summary is presented of up-to-date sample preparation methods and instrumental techniques applied for the detection and quantification of bisphenol A and its structural analogues in various biological matrices. Biological matrices such as blood, cell-free blood products, urine, saliva, breast milk, cordial blood, amniotic and semen fluids, as well as sweat and hair, are very complex; therefore, the detection and later quantification of bisphenols at low levels present a real analytical challenge. The most popular analytical approaches include gas and liquid chromatography coupled with mass spectrometry, and their enhanced reliability and sensitivity finally allow the separation and detection of bisphenols in biological samples, even as ultra-traces. Liquid/liquid extraction (LLE) and solid-phase extraction (SPE) are still the most common methods for their extraction from biological matrices. However, many modern and environmentally safe microextraction techniques are currently under development. The complexity of biological matrices and low concentrations of analytes are the main issues for the limited identification, as well as understanding the adverse health effects caused by chronical and ubiquitous exposure to bisphenols and its analogues.

Competition-Based Two-Dimensional Photonic Crystal Dually Cross-Linked Supramolecular Hydrogel for Colorimetric and Fluorescent Dual-Mode Sensing of Bisphenol A

Bisphenol A (BPA), one of the most abundantly produced endocrine disrupting chemicals, is widely used in everyday plastic products and thus must be monitored. Multimode sensing platforms are able to combine the advantages of different strategies while solving the issues of inaccurate test results of single signal sensing. However, the exploration in this field is limited due to the compromise of sensing conditions and inevitable mutual interferences of different systems. Herein, we constructed a two-dimensional photonic crystal dually cross-linked supramolecular hydrogel (2DPCDCSH) by utilizing a host-guest pair of β-cyclodextrin (β-CD) and tert-butyl (t-Bu) as the second cross-linking for colorimetric and fluorescent dual-mode sensing of BPA. Based on the fact that BPA can act as a competitive guest to break the host-guest interaction between β-CD and t-Bu, the cross-linking density decreased and an expansion-induced structural color change occurred. Sensitive and selective BPA detection can be easily achieved by measuring the Debye diffraction ring diameter or observing the color change of 2DPC with a detection limit of 1 μg mL^-1. Moreover, the formation of the β-CD/BPA complex gave a significant enhancement of the intrinsic fluorescence of BPA, obtaining a detection limit of 0.001 μg mL^-1. The two sensing systems can share the same reaction condition and yield a wider dynamic response range than the single signal strategy. Overall, the proposed method presented an efficient, rapid, cost-effective, and regenerative dual-mode method for BPA analysis and shed new insights for the design of diversified sensing platforms.

A Fast Method for Determination of Seven Bisphenols in Human Breast Milk Samples with the Use of HPLC-FLD

Plastic pollution, where bisphenol A (BPA) is widely used in its production, has gained popularity. BPA omnipresence and toxicity, especially for infants, has led food safety authorities to place restrictions on BPA usage. It has led to the introduction of the marked 'BPA-free'-labelled products, where BPA is often replaced by other bisphenols (BPs) which are suspected of being similar or even more toxic than BPA. Moreover, the free forms of BPs are more dangerous than their conjugated forms and the conjugation of BPs is less effective in infants than in adults. Considering that human breast milk is the main source of nutrition for infants, the constant biomonitoring not only of BPA, but the wider group of BPs in such crucial matrices seems to be vital. In this study, a fast, simple, 'green' and cost-effective DLLME-based extraction technique combined with HPLC-FLD was optimized for the determination of seven selected bisphenols simultaneously. The procedure has satisfactory recovery values of 67-110% with the most RSD% at 17%. The LODs and LOQs ranged from 0.5 ng/mL to 2.1 ng/mL and 1.4 ng/mL to 6.3 ng/mL, respectively. The procedure was successfully applied to the biomonitoring of free forms of BPs in 10 real human breast milk samples.

Competitive removal mechanism to simultaneously incarcerate bisphenol A, triclosan and 4-tert-octylphenol within beta-cyclodextrin crosslinked citric acid used for encapsulation in polypropylene membrane protected-micro-solid-phase extraction

Endocrine disrupting compounds (EDCs) are extensively found in the environment and severely impacting human health. In addressing this issue, the beta-cyclodextrin crosslinked citric acid (BCD-CA) had been previously employed in membrane-protected micro-solid phase extraction for sequestering EDCs from water medium; and the findings revealed that BCD-CA possessed a selectivity property. On that account, the potential of BCD-CA towards competitive adsorption of selected EDCs was investigated in terms of adsorption mechanism and selectivity property. Factors that affected the removal efficiencies such as sample pH, sorbent dosage, contact time and initial concentration were evaluated. The characterization results revealed that the carbon percentage of BCD-CA had increased by 2.04%, while the hydrogen percentage had reduced by 1.83%, signifying the successful crosslinking of BCD-CA. Besides, the amount of active BCD was calculated to be 3.2 × 10^-7 mol, while the amount of carboxyl group was 2.48 × 10^-5 mol per 4 mg of BCD-CA. Moreover, BCD-CA was stable in an aqueous medium with the zeta potential obtained at -36.5 mV and had a high-water retention capacity (∼150%). The competitive adsorption mechanism by BCD-CA with EDCs followed the pseudo-second-order kinetics and Freundlich isotherm, suggesting that the adsorption process was dominated by chemisorption on the heterogeneous surface of the adsorbent. Thermodynamic results revealed that adsorption of 4-tert-octylphenol had the most negative ΔG value, indicating most favorable to be adsorbed by BCD-CA as opposed to triclosan and bisphenol A, which was coherent with the apparent formation constant results. These unique properties manifested the practicality of BCD-CA as a selective adsorbent to detect and remove EDCs from the water medium.

An efficient 3D adsorbent foam based on graphene oxide/AgO nanoparticles for rapid vortex-assisted floating solid phase extraction of bisphenol A in canned food products

In this study, a three-dimensional adsorbent was developed based on graphene oxide/AgO nanoparticles over interconnected nickel foam (GO/AgO@Ni foam) for rapid and efficient vortex assisted floating solid phase extraction of bisphenol A in canned food products prior to high performance liquid chromatography with a fluorescence detector. The analytical techniques scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared (FT-IR) were used for characterization of the synthetized GO/AgO@Ni foam. The effect of proficiency factors including pH, foam size, vortexing time, salt addition, sample volume, desorption type and volume, and desorption time on the extraction efficiency of bisphenol A were explored through the matrix match method. Under the above experimental conditions, the figures of merit of the method were acquired as LODs (S/N = 3) of 0.18-0.84 μg kg^-1, LOQs of 0.61-2.81 μg kg^-1 (S/N = 10), linear ranges of 0.5-500 μg kg^-1, and enrichment factors of 235.5-244.9. The inter-day precision values (RSD%, n = 7) of 2.5-3.6 and the intra-day precision (%) of (5 days and seven replicates for each day) 2.8-3.8 were achieved for bisphenol A at a concentration of 50 μg kg^-1. The relative recoveries of 94.0% to 99.6% were obtained for the canned food samples.

Recent Advances in Solid-Phase Extraction as a Platform for Sample Preparation in Biomarker Assay

Low levels of biomarkers and the complexity of bio sample make the analytical assay of several biomarkers a challenging issue. Suitable sample preparation run remain a vital part of the puzzle of diagnostic level. Enhancing the detection limit of bioanalytical methods start during the sample preparation procedure. A robust sample preparation method is needed to evaluate the number of biomarkers. As worldwide environmental issues attract expanding consideration, all the more harmless to the ecosystem investigations are liked. Solid-phase extraction (SPE) is an appealing strategy among the sample treatment methods due to the versatility of sorbent materials, less solvent consumption, and compatibility with analytical devices. Miniaturization of the SPE gives the chance to integrate the other analytical steps in a single run, known as an easy-to-use and effective method. SPE utilizes various SPE sorbent beds such as packed beads, porous polymer monoliths, molecularly imprinted polymers, membranes, or other magnetic form microstructures to achieve high surface-to-volume ratio and appropriate chemical properties effective extraction. Also, SPE is the methodology of interest to fulfill high recovery and efficiency demands. In this review, we intend to explain more recent methods for the rational design of SPE and miniaturized SPE to determine biomarkers from biological media. The headlines are subdivided into (1) packing materials in SPE, (2) setups for sample preparation by magnetic SPE, and (3) and future perspective for the application of SPE in sample preparation for analysis of biomarkers.

State of the art on the ultrasonic-assisted removal of environmental pollutants using metal-organic frameworks

The environmental and health issues of drinking water and effluents released into nature are among the major area of contention in the past few decades. With the growth of ultrasound-based approaches in water and wastewater treatment, promising materials have also been considered to employ their advantages. Metal-organic frameworks (MOFs) are among the porous materials that have received great attention from researchers in recent years. Features such as high porosity, large specific surface area, electronic properties like semi-conductivity, and the capacity to coordinate with the organic matter have resulted in a substantial increase in scientific researches. This work deals with a comprehensive review of the application of MOFs for ultrasonic-assisted pollutant removal from wastewater. In this regard, after considering features and synthesis methods of MOFs, the mechanisms of several ultrasound-based approaches including sonocatalysis, sonophotocatalysis, and sono-adsorption are well assessed for removal of different organic compounds by MOFs. These methods are compared with some other water treatment processes with the application of MOFs in the absence of ultrasound. Also, the main concern about MOFs including environmental hazards and water stability is fully discussed and some techniques are proposed to reduce hazardous effects of MOFs and improve stability in humid/aqueous environments. Economic aspects for the preparation of MOFs are evaluated and cost estimates for ultrasonic-assisted AOP approaches were provided. Finally, the future outlooks and the new frontiers of ultrasonic-assisted methods with the help of MOFs in global environmental pollutant removal are presented.

Beta-Cyclodextrin-Decorated Magnetic Activated Carbon as a Sorbent for Extraction and Enrichment of Steroid Hormones (Estrone, β-Estradiol, Hydrocortisone and Progesterone) for Liquid Chromatographic Analysis

A β-cyclodextrin-decorated magnetic activated carbon adsorbent was prepared and characterized using various analytical techniques (X-ray diffraction (XRD), scanning electron microscopy–electron diffraction spectroscopy (SEM-EDS) and transmission electron microscopy (TEM)), and the adsorbent was used in the development of a magnetic solid-phase microextraction (MSPE) method for the preconcentration of estrone, β-estradiol, hydrocortisone and progesterone in wastewater and river water samples. This method was optimized using the central composite design in order to determine the experimental parameters affecting the extraction procedure. The quantification of hormones was achieved using high-performance liquid chromatography equipped with a photodiode array detector (HPLC-DAD). Under optimum conditions, the linearity ranged from 0.04 to 300 µg L⁻¹ with a correlation of determinations of 0.9969–0.9991. The limits of detection and quantification were between 0.01–0.03 and 0.033–0.1 µg L⁻¹, with intraday and interday precisions at 1.1–3.4 and 3.2–4.2. The equilibrium data were best described by the Langmuir isotherm model, and high adsorption capacities (217–294 mg g⁻¹) were obtained. The developed procedure demonstrated high potential as an effective technique for use in wastewater samples without significant interferences, and the adsorbent could be reused up to eight times.

Magnetic porous carbons derived from iron-based metal-organic framework loaded with glucose for effective extraction of synthetic organic dyes in drinks

The conversion of metal-organic frameworks (MOFs) to porous carbon has attracted extensive attention for developing multifunctional adsorbent materials. Herein, we demonstrated a facile method to prepare magnetic porous carbon via calcinating MIL-101(Fe) precursor loaded with glucose at 700 °C in an N₂ atmosphere. The obtained magnetic porous carbon (MPCG) contained plenty of oxygen-containing functional groups and exhibited an enlarged specific surface area (177.7 m²/g) compared with its precursor (41.2 m²/g). In addition, MPCG can be easily separated from the matrix by a magnet. Benefitting from these advantages, the magnetic porous carbon exhibited high affinity toward four synthetic organic dyes (amaranth, ponceau 4R, sunset yellow, and lemon yellow) in an aqueous solution. Moreover, the adsorbent can be applied to quantitatively detect synthetic organic dyes in drinks coupled with chromatography. A new magnetic solid-phase extraction method for dye analysis yielded reasonable linearity (r □ 0.99), low limits of detection (0.047-0.076 μg/L), and good precision within the analyte concentration range of 0.25-50 μg/L.

On the use of metal-organic frameworks for the extraction of organic compounds from environmental samples

The determination of trace metals and organic contaminants in environmental samples, such as water, air, soil, and sediment, is until today a challenging process for the analytical chemistry. Metal-organic frameworks (MOFs) are novel porous nanomaterials that are composed of metal ions and an organic connector. These materials are gaining more and more attention due to their superior characteristics, such as high surface area, tunable pore size, mechanical and thermal stability, luminosity, and charge transfer ability between metals and ligands. Among the various applications of MOFs are gas storage, separation, catalysis, and drug delivery. Recently, MOFs have been successfully introduced in the field of sample preparation for analytical chemistry and they have been used for sample pretreatment of various matrices. This review focuses on the applications of MOFs as novel adsorbents for the extraction of organic compounds from environmental samples.

Polyvinylpyrrolidone-assisted synthesis of highly water-stable cadmium-based metal-organic framework nanosheets for the detection of metronidazole

Recently, much effort has been dedicated to ultra-thin two-dimensional metal–organic framework (2D MOF) nanosheets due to their outstanding properties, such as ultra-thin morphology, large specific surface area, abundant modifiable active sites, etc. However, the preparation of high-quality 2D MOF nanosheets in good yields still remains a huge challenge. Herein, we report 2D cadmium-based metal–organic framework (Cd-MOF) nanosheets prepared in a one-pot polyvinylpyrrolidone (PVP)-assisted synthesis method with high yield. The Cd-MOF nanosheets were characterized with good stability and dispersion in aqueous systems, and were highly selective and sensitive to the antibiotic metronidazole (MNZ) with low limit of detection (LOD: 0.10 μM), thus providing a new and promising fluorescent sensor for rapid detection of MNZ in aqueous solution.

Except PVP was added for Cd-MOF nanosheets, the preparation process of bulk and Cd-MOF nanosheets was similar.

Recent advances in analysis of bisphenols and their derivatives in biological matrices

Biomonitoring is a very useful tool to evaluate human exposure to endocrine-disrupting compounds (EDCs), like bisphenols (BPs), which are widely used in the manufacture of plastics. The development of reliable analytical methods is key in the field of public health surveillance to obtain biomonitoring data to determine what BPs are reaching people's bodies. This review discusses recent methods for the quantitative measurement of bisphenols and their derivatives in biological samples like urine, blood, breast milk, saliva, and hair, among others. We also discuss the different procedures commonly used for sample treatment, which includes extraction and clean-up, and instrumental techniques currently used to determine these compounds. Sample preparation techniques continue to play an important role in the analysis of complex matrices, for liquid matrices the most commonly employed is solid-phase extraction, although microextraction techniques are gaining importance in this field, and for solid samples ultrasound-assisted extraction. The main instrumental techniques used are liquid and gas chromatography coupled with mass spectrometry. Finally, we present data on the main parameters obtained in the validation of the revised methods. This review focuses on various methods developed and applied for trace analysis of bisphenols, their conjugates, halogenated derivatives, and diglycidyl ethers in biological samples to enable the required selectivity and sensitivity. For this purpose, a review is carried out of the most recent relevant publications from 2016 up to present.

Recent advances in the extraction of triazine herbicides from water samples

Pesticides are excessively used in agriculture to improve the quality of crops by eliminating the negative effects of pests. Among the different groups of pesticides, triazine pesticides are a group of compounds that contain a substituted C₃ H₃ N₃ heterocyclic ring, and they are widely used. Triazine pesticides can be dangerous for humans as well as for the aquatic environment because of their high toxicity and endocrine disrupting effect. However, the concentration of these chemical compounds in water samples is low. Moreover, other compounds that may exist in the water samples can interfere with the determination of triazine pesticides. As a result, it is important to develop sample preparation methods that provide preconcentration of the target analyte and sufficient clean-up of the samples. Recently, a wide variety of novel microextraction and miniaturized extraction techniques (e.g., solid-phase microextraction and liquid-phase microextraction, stir bar sorptive extraction, fabric phase sorptive extraction, dispersive solid-phase extraction, and magnetic solid-phase extraction) have been developed. In this review, we aim to discuss the recent advances regarding the extraction of triazine pesticides from environmental water samples. Emphasis will be given to novel sample preparation methods and novel sorbents developed for sorbent-based extraction techniques.

Green Bioanalytical Applications of Graphene Oxide for the Extraction of Small Organic Molecules

Bioanalysis is the scientific field of the quantitative determination of xenobiotics (e.g., drugs and their metabolites) and biotics (e.g., macromolecules) in biological matrices. The most common samples in bioanalysis include blood (i.e., serum, plasma and whole blood) and urine. However, the analysis of alternative biosamples, such as hair and nails are gaining more and more attention. The main limitations for the determination of small organic compounds in biological samples is their low concentration in these matrices, in combination with the sample complexity. Therefore, a sample preparation/analyte preconcentration step is typically required. Currently, the development of novel microextraction and miniaturized extraction techniques, as well as novel adsorbents for the analysis of biosamples, in compliance with the requirements of Green Analytical Chemistry, is in the forefront of research in analytical chemistry. Graphene oxide (GO) is undoubtedly a powerful adsorbent for sample preparation that has been successfully coupled with a plethora of green extraction techniques. GO is composed of carbon atoms in a sp² single-atom layer of a hybrid connection, and it exhibits high surface area, as well as good mechanical and thermal stability. In this review, we aim to discuss the applications of GO and functionalized GO derivatives in microextraction and miniaturized extraction techniques for the determination of small organic molecules in biological samples.

Metal-Organic Frameworks in Bioanalysis: Extraction of Small Organic Molecules

The quantitative determination of xenobiotic compounds, as well as biotics in biological matrices, is generally described with the term bioanalysis. Due to the complexity of biofluids, in combination with the low concentration of the small molecules, their determination in biological matrices is a challenging procedure. Apart from the conventional solid-phase extraction, liquid-liquid extraction, protein precipitation, and direct injection approaches, nowadays, a plethora of microextraction and miniaturized extraction techniques have been reported. Furthermore, the development and evaluation of novel extraction adsorbents for sample preparation has become a popular research field. Metal-organic frameworks (MOFs) are novel materials composed of metal ions or clusters in coordination with organic linkers. Unequivocally, MOFs are gaining more and more attention in analytical chemistry due to their superior properties, including high surface area and tunability of pore size and functionality. This review discusses the utilization of MOFs in the sample preparation of biological samples for the green extraction of small organic molecules. Their common preparation and characterization strategies are discussed, while emphasis is given to their applications for green sample preparation.

Surfactant-coupled titanium dioxide coated iron-aluminium mixed metal hydroxide for magnetic solid phase extraction of bisphenols in carbonated beverages

In this work, the magnetic sorbents based on different surfactant-coupled titanium dioxide coated iron-aluminium mixed metal hydroxide were investigated as sorbent for extraction of bisphenol compounds. The structure, morphology, and magnetic property of the synthesized sorbents were investigated. The cetyltrimethylammonium bromide-titanium dioxide coated iron-aluminium mixed metal hydroxide (Fe-Al MMH@TiO2-CTAB) exhibited excellent extraction performance toward bisphenols and was selected as the sorbent for development of magnetic solid phase extraction (MSPE) method. The entire MSPE process was optimized, and the extract was analyzed by high performance liquid chromatography with photodiode array detector. The method provided wide linear calibration ranges for bisphenols between 0.3-6000 μg L-1 with maximum enrichment factors of 280. The limits of detection and limits of quantification were in the ranges of 0.08-0.3 and 0.3-1.0 μg L-1, respectively. The proposed MSPE method was tested for determination of bisphenols in carbonated beverages. The studied carbonated beverages were mostly free of bisphenol contamination; however, BPS, BPA and BPB were detected in samples taken from defective cans. The relative recoveries ranging of 80.2-118.9% were obtained. The as-prepared Fe-Al MMH@TiO2-CTAB sorbent provided high sorption capacities in the range of 2215-2451 mg kg-1 and could be a promising material for bisphenols in beverage samples.

Green bioanalytical sample preparation: fabric phase sorptive extraction

Fabric phase sorptive extraction (FPSE) is a recently introduced sample preparation technique that has attracted substantial interest of the scientific community dealing with bioanalysis. This technique is based on a permeable and flexible substrate made of fabric, coated with a sol-gel organic-inorganic sorbent. Among the benefits of FPSE are its tunable selectivity, adjustable porosity, minimized sample preparation workflow, substantially reduced organic solvent consumption, rapid extraction kinetics and superior extraction efficiency, many of which are well-known criteria for Green Analytical Chemistry. As such, FPSE has established itself as a leading green sample preparation technology of 21st century. In this review, we discuss the principal steps for the development of an FPSE method, the main method optimization strategies, as well as the applications of FPSE in bioanalysis for the extraction of a wide range of analytes (e.g., estrogens, benzodiazepines, androgens and progestogens, penicillins, anti-inflammatory drugs, parabens etc.).

[Research progress in the application of magnetic solid phase extraction based on carbon based magnetic materials in food analysis]

Trace toxic substances in food pose a serious threat to human health, and need to be detected and analyzed to ensure food safety. However, there are many kinds of toxic substances in food, with small amounts and complex matrices, making it necessary to select an appropriate sample pretreatment technology for extraction and purification. There are some disadvantages to sample pretreatment methods such as solid phase extraction and liquid-liquid extraction, in terms of poor selectivity, significant influence of matrix interference, large sample requirement, long extraction time, use of a large amount of harmful organic solvents, and cumbersome and time-consuming operation. Magnetic solid phase extraction (MSPE) combines the advantages of magnetic separation and traditional SPE technology, avoids time-consuming column loading, and can extract the target analyte efficiently. Because of its advantages, in that it has simple operation, is time-saving and fast, requires no centrifugal filtration, and is environmentally friendly, it is considered an efficient sample pretreatment technology and applied in food analysis. The adsorption capacity and selectivity of the magnetic adsorbent used in MSPE are the key factors affecting the extraction efficiency and selectivity of MSPE, and play a key role in the accuracy of the established method. Carbon-based magnetic materials are a type of new functional magnetic materials prepared by the co-precipitation of carbon-based materials (carbon nanotubes, graphene, metal-organic framework-derived carbon, or activated carbon) and magnetic materials. In order to endow carbon-based magnetic materials with the advantages of both, carbon materials and magnetic materials, while also reflecting the advantages of high specific surface area, good stability, low cost, environmental friendliness, excellent physical and chemical properties, high porosity, and high adsorption capacity, proper functional modification is needed. Carbon-based magnetic materials modified by functionalization can efficiently enrich organic and inorganic analytes with different properties, and have seen significant progress in environmental analysis, biological detection, pollution control, and other fields. In recent years, MSPE technology based on carbon-based magnetic materials has been gradually applied in food analysis and pretreatment, but its use is still in infancy and holds immense application potential. Reference to more than 50 papers published in SCI and Chinese core journals over the past four years reveals that carbon-based materials include carbon nanotubes modified by functional groups, reagents, or materials; graphene, graphene oxide, and reduced graphene oxide; carbon derived from a gold organic framework; activated carbon biochar; and nanodiamond. The harmful substances in food samples include esters, mycotoxins, polycyclic aromatic hydrocarbons, antibiotics, alkaloids, phenols, vitamins, and antibiotics. Based on the classification of carbon-based materials, this review reveals that carbon-based magnetic materials have good preconcentration ability for harmful substances in food samples. MSPE can be combined with GC-MS, liquid chromatography-high resolution mass spectrometry (LC-HRMS), ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS), ultra high performance liquid chromatography-Q-Exactive high resolution mass spectrometry (UHPLC-Q-Exactive HRMS), high performance liquid chromatography-diode array detection (HPLC-DAD), gas chromatography micro-electron capture detection (GC-μECD), high performance liquid chromatography fluorescence with post-column photochemical derivatization (HPLC-PCD-FLD), and HPLC-UV to analyze food samples. These combined technologies have high accuracy and recovery. However, the synthesis methods of carbon-based magnetic materials such as carbon nanotubes and graphene, incur high energy consumption and high cost, and involve complex processes, which limit their application. Therefore, a carbon-based magnetic adsorbent with low cost, high selectivity, and high extraction efficiency was developed by further exploring functional modification with biochar as a carbon base. This is a very promising direction to develop MSPE technology utilizing biochar-based magnetic materials for food sample pretreatment. This review provides a theoretical basis and technical support for the wide application of carbon-based magnetic materials in MSPE technology for food analysis.

Evaluation of sewage sludge biochar and modified derivatives as novel SPE adsorbents for monitoring of bisphenol A

Sewage sludge is abundant biomass, the sustainable management of which remains a big issue worldwide. It was demonstrated that pyrolysis of sewage sludge using simple and cost-effective apparatus can produce biochars, suitable for solid-phase extraction applications of hydrophobic analytes. Detailed characterization showed that modification lead to three more hydrophobic and one more hydrophilic sample, compared to the original biochar. All samples were evaluated in the solid-phase extraction of the emerging contaminant Bisphenol A from aqueous solutions. KOH-SSB and KOH/MeOH-SSB exhibited the most promising behavior, with the latter achieving recoveries of 88.1%, at a quantity of 0.1 g at the natural pH of the BPA solution (6.5). The effect of solution pH was insignificant in the range of 4-7, whereas the initial BPA concentration had no effect in the recovery within the range of 1-100 μg L^-1. The mechanism of interaction between the optimum sample and BPA was based on hydrogen bonding and π-π interactions, establishing earlier observations that the type (and not concentration) of individual surface groups and the total surface area play a significant role in the process.

Ultrasound-assisted magnetic solid-phase extraction of polycyclic aromatic hydrocarbons and nitrated polycyclic aromatic hydrocarbons from water samples with a magnetic polyaniline modified graphene oxide nanocomposite

A novel magnetic graphene oxide nanocomposite modified with polyaniline (Fe₃O₄@GO-PANI) was synthesized and applied for the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons (PAHs) (i.e. fluorene, phenanthrene and pyrene) and nitrated polycyclic aromatic hydrocarbons (N-PAHs) (i.e. 2-nitrofluorene, 9-nitroanthracene, 1-nitropyrene and 3-nitrofluoranthene) prior to their determination by gas chromatography-mass spectrometry. The prepared nanomaterial was characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform-infrared spectroscopy. The main experimental parameters affecting the extraction and desorption steps of the MSPE procedure were investigated and optimized. Under optimum conditions, coefficients of determination (r²) ranged between 0.9970 and 0.9995, limits of detection (LODs, S/N = 3) ranged between 0.04-0.05 ng mL^-1 for PAHs and 0.01-0.11 ng mL^-1 for N-PAHs, while the relative standard deviation for intra-day and inter-day repeatability were lower than 10.0% for PAHs and N-PAHs. The method was successfully applied to the analysis of tap, mineral and river water samples. Relative recoveries in spiked water samples ranged between from 91.6 to 114% and from 92.3 to 110% for PAHs and N-PAHs, respectively. The proposed method is simple, rapid, sensitive and the Fe₃O₄@GO-PANI sorbent can be reused for at least 15 times without significant decrease in extraction recovery.

Determination of phenolic compounds in estuary water and sediment by solid-phase isotope dansylation coupled with liquid chromatography-high resolution mass spectrometry

A method consisting of solid-phase isotope dansylation (derivatization with dansyl chloride) and liquid chromatography-high resolution mass spectrometry (LC-HRMS) was developed for the quantitative analysis of phenolic compounds (phenols) in environmental samples. A magnetic-HLB (hydrophilic lipophilic balanced) material was synthesized and applied as an adsorbent in magnetic solid-phase extraction (MSPE) for the enrichment of the analytical targets. Furthermore, with the solid-phase isotope labeling, the desalting and removal of labeling residuals could be simplified over conventional in-solution labeling. In addition to overcoming the matrix effect by isotope dansylation, the sensitivity for the analysis of phenols by LC-HRMS was remarkably improved by over 100-fold. The method was systematically verified, and good accuracy (86.5-104.9%) and precision (<8.6% and <11.4% for intra- and inter-day, respectively) were achieved for the tested 15 phenols. The limits of detection (LODs) of this method were estimated to be 0.2-5 ng L^-1 and 5-100 ng kg^-1 in estuary water and sediment samples, respectively. With this method, samples collected from the Daliao River estuary (Panjin, China) were analyzed. It was found that all of the targeted phenols were detected at concentrations ranging from unquantifiable to 485 ng L^-1 (the total concentration of analytes found in each sample were in the range 822-957 ng L^-1) and unquantifiable to 1368 ng kg^-1 (the total concentration of analytes found in each sample were in the range 2251-2992 ng kg^-1) in water and sediment, respectively.

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.

Greenness of magnetic nanomaterials in miniaturized extraction techniques: A review

Green analytical chemistry principles should be followed, as much as possible, and particularly during the development of analytical sample preparation methods. In the past few years, outstanding materials such as ionic liquids, metal-organic frameworks, carbonaceous materials, molecularly imprinted materials, and many others, have been introduced in a wide variety of miniaturized techniques in order to reduce the amount of solvents and sorbents required during the analytical sample preparation step while pursuing more efficient extraction methods. Among them, magnetic nanomaterials (MNMs) have gained special attention due to their versatile properties. Mainly, their ability to be separated from the sample matrix using an external magnetic field (thus enormously simplifying the entire process) and their easy combination with other materials, which implies the inclusion of a countless number of different functionalities, highly specific in some cases. Therefore, MNMs can be used as sorbents or as magnetic support for other materials which do not have magnetic properties, the latter permiting their combination with novel materials. The greenness of these magnetic sorbents in miniaturized extractions techniques is generally demonstrated in terms of their ease of separation and amount of sorbent required, while the nature of the material itself is left unnoticed. However, the synthesis of MNMs is not always as green as their applications, and the resulting MNMs are not always as safe as desired. Is the analytical sample preparation field ready for using green magnetic nanomaterials? This review offers an overview, from a green analytical chemistry perspective, of the current state of the use of MNMs as sorbents in microextraction strategies, their preparation, and the analytical performance offered, together with a critical discussion on where efforts should go.

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.

Activated carbon/diatomite-based magnetic nanocomposites for magnetic solid-phase extraction of S-phenylmercapturic acid from human urine

In this study, activated carbon/diatomite-based magnetic nancomposites (denoted as AC/DBMNs) were synthesized and applied as an adsorbent for magnetic solid-phase extraction of S-phenylmercapturic acid (S-PMA) from human urine prior to high-performance liquid chromatography. The surface morphologies and structures of AC/DBMNs were characterized by Fourier transform infrared spectroscopy, transmission and scanning electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area, vibrating sample magnetometer and ζ-potential measurements. The experimental parameters including sample volume, sample pH, adsorbent amount, extraction time, elution solvent and desorption time were investigated in detail. Under the optimum conditions, the method exhibited good linearity (r > 0.9993) within the concentration ranges of 0.03-1.0 mg/L. Moreover, the limits of detection and quantification were 0.01 and 0.03 mg/L, respectively. The enrichment factor was 5, and good recoveries (88.9-97.3%) with relative standard deviations in the range of 5.6-6.8% (n = 6) for inter-day and 6.3-8.1% (n = 6) for intra-day were achieved. The developed method was successfully applied to the analysis of S-PMA in urine samples. In addition, this accurate and sensitive method has great potential to be applied in the early screening and clinical diagnosis of the workers exposed to benzene.

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.

Endocrine Disruptors Induced Distinct Expression of Thyroid and Estrogen Receptors in Rat versus Mouse Primary Cerebellar Cell Cultures

The endocrine system of animals consists of fine-tuned self-regulating mechanisms that maintain the hormonal and neuronal milieu during tissue development. This complex system can be influenced by endocrine disruptors (ED)—substances that can alter the hormonal regulation even in small concentrations. By now, thousands of substances—either synthesized by the plastic, cosmetic, agricultural, or medical industry or occurring naturally in plants or in polluted groundwater—can act as EDs. Their identification and testing has been a hard-to-solve problem; Recent indications that the ED effects may be species-specific just further complicated the determination of biological ED effects. Here we compare the effects of bisphenol-A, zearalenone, and arsenic (well-known EDs) exerted on mouse and rat neural cell cultures by measuring the differences of the ED-affected neural estrogen- and thyroid receptors. EDs alters the receptor expression in a species-like manner detectable in the magnitude as well as in the nature of biological responses. It is concluded that the interspecies differences (or species specificity) in ED effects should be considered in the future testing of ED effects.

Core-shell structured magnetic mesoporous carbon nanospheres derived from metal-polyphenol coordination polymer-coated Fe3 O4 and its application in the enrichment of phthalates from water samples

In this work, core-shell structured magnetic mesoporous carbon nanospheres were fabricated from the carbonization of metal-polyphenol coordination polymer-coated Fe₃ O₄ nanoparticles. The preparation method is simple, fast, versatile, and easy to scale up. Magnetic mesoporous carbon nanospheres exhibit a high specific surface area, high superparamagnetism, and high adsorption efficiencies for phthalates. Four phthalates were extracted from aqueous solutions by using magnetic mesoporous carbon nanospheres via magnetic solid phase extraction. Subsequent analysis was performed by using high-performance liquid chromatography with ultraviolet detection. The analytical method has good linearity in the concentration range of 1-200 ng/mL for diethyl phthalate, diisobutyl phthalate, and dicyclohexyl phthalate, and 3-200 ng/mL for dipropyl phthalate. The limits of detection were in the range of 0.10-0.62 ng/mL. Compared with previous methods, this method has a lower detection limit, wider linearity range, and faster adsorption and desorption rates. The results indicate that magnetic mesoporous carbon nanospheres are suitable for the enrichment of hydrophobic substances from aqueous solutions.

Easy and Inexpensive Method for Multiclass Analysis of 41 Food Contact Related Contaminants in Fatty Food by Liquid Chromatography-Tandem Mass Spectrometry

Food contact materials (FCMs) may release their chemical components into food and thus raise safety concerns. This paper attempted to study the presence of four major groups of FCM-related endocrine disruptors in fatty food: dialkyl phthalates, bisphenols, printing ink photoinitiators, and polyfluoroalkyl substances. All 41 target compounds were analyzed simultaneously by means of liquid chromatography coupled to tandem mass spectrometry. The sample preparation was significantly streamlined to reduce analysis costs by employing acetonitrile extraction, extract modification by water, and refrigeration at 5 °C. The new method was validated and applied to 60 real samples, including edible oils, butter, and chocolate, where 16 target compounds were measured at levels ≤13000 ng/g. The study also described the blank level increase and sensitivity loss caused by impurities present in the HPLC methanol solvent.

Graphene Oxide Based Magnetic Nanocomposites with Polymers as Effective Bisphenol-A Nanoadsorbents

Magnetic graphene oxide was impregnated with polymers for the preparation of nanocomposite adsorbents to be examined for the adsorptive removal of a typical endocrine disruptor, bisphenol–A (BPA) from aqueous solutions. The polymers used were polystyrene, chitosan and polyaniline. The nanocomposites prepared were characterized for their structure, morphology and surface chemistry. The nanocomposites presented an increase adsorptive activity for BPA at ambient conditions, compared to pure magnetic oxide, attributed to the synergistic effect of the polymers and the magnetic graphene oxide. The increased adsorption of BPA exhibited by the nanocomposites with chitosan and polyaniline could be attributed to the contribution of amine groups.