Magnetic solid-phase extraction for the removal of mercury from water with ternary hydrosulphonyl-based deep eutectic solvent modified magnetic graphene oxide

Novel poly-deep eutectic solvent-functionalized magnetic graphene oxide nanomaterials for high-performance solid-phase extraction of trypsin

Three novel polymethacrylic acid-based deep eutectic solvent (DES)-functionalized magnetic graphene oxide composites were designed and successfully synthesized via the radical polymerization method. The aim was to achieve the selective solid-phase extraction of trypsin (Tryp). Among them, the magnetic extractant (MGO@PDES2) functionalized with a poly-deep eutectic solvent composed of tetraethylammonium chloride and methylpropionic acid at a molar ratio of 1 : 2 exhibited the highest extraction efficiency for Tryp. Owing to the high specific surface area of MGO and the abundant carboxyl functional groups in PDES2, the prepared MGO@PDES2 exhibited excellent selectivity and stability for Tryp extraction. Under optimal conditions, the extraction capacity of Tryp by MGO@PDES2 reached 708.85 mg g-1. The extraction driving forces between MGO@PDES2 and Tryp were hydrogen-bonding interactions and electrostatic interactions. Among the seven biomacromolecules, MGO@PDES2 displayed outstanding selectivity for Tryp. In addition, the results of cycling experiments indicated that MGO@PDES2 could be reused many times without a significant change in extraction capacity. Moreover, the proposed method was successfully applied to extract Tryp from the crude extract of bovine pancreas, yielding satisfactory results. All the results suggest that MGO@PDES2 is a promising magnetic extractant, which is expected to provide new ideas for the extraction and separation of proteins.

Deep eutectic solvent as stationary phase for flow analysis: Automated trace metal determination in food products

BACKGROUND

Deep eutectic solvents (DES) have emerged as effective solvents that address many challenges in analytical chemistry, particularly in microextraction. However, until now, their use has been primarily focused on extraction processes. This has significantly limited their application in analytical chemistry, especially in flow analysis, where the high viscosity of DES has made their use difficult.

RESULTS

This paper presents a novel DES-based liquid-liquid microextraction approach for the separation and determination of trace metals in foods using an automated flow analysis system. In this study, a DES composed of thymol and thionalide was first prepared and thoroughly characterized by spectroscopic (IR, NMR) and differential scanning calorimetry techniques. The COSMO-SAC model was employed to predict the solubility of metal salts (Cu, Cd, Pb, and Hg) in the new DES. The solvent was applied to glass fiber as a stationary phase in an extraction column in a flow analysis. After microwave digestion of food samples, metals were extracted by this DES in an automated mode and subsequently eluted with an aqueous thiourea solution. The procedure demonstrated limits of detection (LOD) of 6 μg kg-1 for mercury, 4 μg kg-1 for copper, 6 μg kg-1 for lead and 0.6 μg kg-1 for cadmium.

SIGNIFICANCE

This study represents the first application of a DES-based stationary phase in automated flow analysis, significantly enhancing extraction efficiency. The procedure enables precise and reliable determination of trace metals in food products, aligning with green chemistry principles by minimizing waste.

An overview on human exposure, toxicity, solid-phase microextraction and adsorptive removal of perfluoroalkyl carboxylic acids (PFCAs) from water matrices

Perfluoroalkyl carboxylic acids (PFCAs) are sub-class of perfluoroalkyl substances commonly detected in water matrices. They are persistent in the environment, hence highly toxic to living organisms. Their occurrence at trace amount, complex nature and prone to matrix interference make their extraction and detection a challenge. This study consolidates current advancements in solid-phase extraction (SPE) techniques for the trace-level analysis of PFCAs from water matrices. The advantages of the methods in terms of ease of applications, low-cost, robustness, low solvents consumption, high pre-concentration factors, better extraction efficiency, good selectivity and recovery of the analytes have been emphasized. The article also demonstrated effectiveness of some porous materials for the adsorptive removal of the PFCAs from the water matrices. Mechanisms of the SPE/adsorption techniques have been discussed. The success and limitations of the processes have been elucidated.

Simultaneous determination of Co and Pb in P. polyphylla var. yunnanensis by ICP-OES after GO-TiO2-DES-based dispersive micro solid phase extraction

In this work, deep eutectic solvent (DES) was used to modify GO-TiO₂ to synthesize new adsorption material GO-TiO₂-DES nanocomposites. It was first used for dispersive micro solid phase extraction (DMSPE) and combined with inductively coupled plasma optical emission spectrometry (ICP-OES) for simultaneous determination of trace cobalt (Co) and lead (Pb) in natural medicine P. polyphylla var. yunnanensis. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), and the Brunauer-Emmett-Teller (BET) specific surface area were used to characterize. The results showed that GO-TiO₂-DES nanocomposites were successfully prepared and had better adsorption effect on metal ions. The factors affecting the extraction and elution of Co and Pb were optimized, including the type of DES, pH, adsorption time, amount of adsorbent, adsorption temperature, and elution time. Under the optimum conditions, the enhancement factors (EFs) of Co and Pb were 31 and 28, the limits of detection (LODs) were 0.11 and 0.24 μg L^-1, and the limits of quantification (LOQs) were 0.36 and 0.82 μg L^-1, respectively. The results of Co and Pb determined by the established method were in good agreement with those of inductively coupled plasma mass spectrometry (ICP-MS), which verified the accuracy and reliability of the method.

Development of multifarious carrier materials and impact conditions of immobilised microbial technology for environmental remediation: A review

Microbial technology is the most sustainable and eco-friendly method of environmental remediation. Immobilised microorganisms were introduced to further advance microbial technology. In immobilisation technology, carrier materials distribute a large number of microorganisms evenly on their surface or inside and protect them from external interference to better treat the targets, thus effectively improving their bioavailability. Although many carrier materials have been developed, there have been relatively few comprehensive reviews. Therefore, this paper summarises the types of carrier materials explored in the last ten years from the perspective of structure, microbial activity, and cost. Among these, carbon materials and biofilms, as environmentally friendly functional materials, have been widely applied for immobilisation because of their abundant sources and favorable growth conditions for microorganisms. The novel covalent organic framework (COF) could also be a new immobilisation material, due to its easy preparation and high performance. Different immobilisation methods were used to determine the relationship between carriers and microorganisms. Co-immobilisation is particularly important because it can compensate for the deficiencies of a single immobilisation method. This paper emphasises that impact conditions also affect the immobilisation effect and function. In addition to temperature and pH, the media conditions during the preparation and reaction of materials also play a role. Additionally, this study mainly reviews the applications and mechanisms of immobilised microorganisms in environmental remediation. Future development of immobilisation technology should focus on the discovery of novel and environmentally friendly carrier materials, as well as the establishment of optimal immobilisation conditions for microorganisms. This review intends to provide references for the development of immobilisation technology in environmental applications and to further the improve understanding of immobilisation technology.

Analytical perspective and environmental remediation potentials of magnetic composite nanosorbents

The synthesis and application of magnetic nanosorbents to remove emerging pollutants have been considered the best environmental remediation and sustainability option. Incorporating magnetism shortens the treatment time and allows the sorbent to be recovered quickly using external magnetic with many cycles. The implementation of magnetic solid-phase extraction (MSPE) using magnetic materials of different shapes, sizes, and surface morphology can be a valuable tool in applying materials to prepare analytical samples. In MSPE applications, materials with strong magnetic domain can be used as precursors for constructing magnetic composite as a promising sorbent. This article focuses on the most recent and exceptional applications of magnetic adsorbents for preconcentration and removal purposes. Magnetic adsorbents, such as nanoparticles (NPs), foam, sponges, nanocomposites, hydrogels, and beads with multifunctional attributes have been comprehensively studied in terms of preparation procedures, limitations, advantages, and interactions between pollutants and magnetic composites. The role of magnetic sorbents in sample preparation methods, such as simple solid-phase extraction and microextraction, as well as sorptive extraction using a stir bar, was also examined. The use of magnetic adsorbents with analytical techniques, such as solid-phase extraction and solid-phase microextraction improves the method for preparing samples concerning the influential role of magnetic adsorbents. Towards the end, promising features and future outlook are also directed.

Excellent performance separation of trypsin by novel ternary magnetic composite adsorbent based on betaine-urea- glycerol natural deep eutectic solvent modified MnFe2O4-MWCNTs

The effective trypsin purification methods should be established since trypsin plays a crucial role in biosome. In this work, a novel ternary magnetic composite adsorbent (MnFe₂O₄-MWCNTs@B-U-G) with the features of strong specific selectivity, good adsorption effect, simple and efficient separation process, no secondary pollution brought in was prepared by integrating the superior physicochemical properties of ternary based natural deep eutectic solvent, multi-walled carbon nanotubes and MnFe₂O₄. The property, composition and microtopography structure of MnFe₂O₄-MWCNTs@B-U-G were characterized in detail. Combined with magnetic solid-phase extraction, MnFe₂O₄-MWCNTs@B-U-G was utilized to adsorb trypsin. Response surface methodology experiment was prepared under Box-Behnken design to optimize the adsorption conditions and the results showed that the practical maximum adsorption capacity for trypsin was 1020.1 mg g^-1. Besides, the adsorption isotherms, adsorption kinetics, regeneration studies and method validation studies were investigated systematically to evaluate the established adsorption separation system. Mechanism exploration proved that electrostatic interaction, hydrogen bonding interaction and chelation interaction were the dominant forces for the high-performance adsorption of trypsin. The activity of trypsin after elution had been analyzed by UV-vis spectrophotometer and CD spectrometer with three methods, which illustrated that the enzyme activity, conformation and secondary structure of trypsin did not change significantly during the adsorption-desorption process. In addition, the proposed method was successful and practical applicability to isolation trypsin from crude bovine pancreas. As a result, due to the superiority of the MnFe₂O₄-MWCNTs@B-U-G, the proposed method not only exhibites high-performance adsorption of trypsin, but also provides a green and sustainable potential value in the adsorption of biomacromolecule.

Ultrasound-assisted dispersive solid phase extraction for promoting enrichment of ng L-1 level Hg2+ on ionic liquid coated magnetic materials

Herein, we investigated the enrichment behavior of inorganic mercury (Hg²⁺) on magnetic adsorbent with different ultrasound (US) energy field input. The enrichment rate of 0.10 μg L^-1 mercury is increased by 4.5 times after US instead of stirring as dispersion mode. The input of higher frequency and power ultrasound can accelerate the enrichment of magnetic ionic liquid adsorbent and reduce the Hg²⁺ residue, importantly, which has not been reported. The positive correlation between cavitation effect and acoustic frequency and power in imaging experiments documents that US parameters are the key factors affecting the magnetic solid phase extraction. In addition, in-situ desorption and detection of adsorbate and recovery of adsorbent can be realized by slurry vapor generation (SVG) technology. The recovery of Hg²⁺ in four cycles is more than 90%, which indicates that the structure and properties of the material are not affected by the application of US. Hence, the degradation of adsorption properties caused by agglomeration of magnetic materials can be improved by introducing dispersion methods such as US. At the same time, 95% enrichment efficiency and 0.01-1.0 μg L^-1 linear calibration range corresponding to 150 mL sample documents that magnetic ionic liquid adsorbent combined with US and sensitive spectral detector can meet the needs of ng L^-1 level Hg²⁺ analysis in natural water samples.

Deep eutectic solvent-modified mixed iron hydroxide-silica: Application in magnetic solid-phase extraction for enrichment of organochlorine pesticides prior to GC-MS analysis

A new type of magnetic material based on silica-coated mixed iron hydroxides functionalized with deep eutectic solvent was utilized for the magnetic solid-phase extraction of organochlorine pesticides prior to gas chromatography-mass spectrometry analysis. Choline chloride and phenol were selected as the hydrogen bond acceptor and donor, respectively, for preparing the deep eutectic solvent-modified magnetic surface. The modified surface possessed superior enrichment capability for organochlorine pesticides. Under optimal extraction conditions, viz., 10 mg sorbent, 5 mL sample solution, and 200 μL acetone (desorption solvent), linearity was obtained in the range 0.005-200 μg/L, with coefficients of determination greater than 0.997. The limits of detection and quantification were as low as 0.6-10 and 5-60 ng/L, respectively, whereas the enrichment factors were in the range of 31-100. The precisions evaluated in terms of the relative standard deviations of the intra- and inter-day experiments were <4.9 and 7.6%, respectively. The developed method was successfully applied for determining the organochlorine residues in agricultural products. Satisfactory recoveries in the range of 71.2-110.3% were obtained, with a relative standard deviation of <8.0%. The proposed material is a promising sorbent for the preconcentration of organochlorine residues.

Magnetic Dispersive Solid Phase Extraction Using Recycled-graphite for GO-Fe3O4-dithizone Composite Combined with FAAS for Determination of Lead in Environmental Samples

Magnetic dispersive solid phase extraction (MdSPE) was developed to determine the concentration of lead (Pb) in real water samples, while graphene oxide-magnetite-dithizone (GO-Fe₃O₄-DTZ) from the used graphite tubes (recycled graphite) of electrothermal technique was simply employed as a new sorbent to improve extraction efficiency, separated by external magnetic field and analyzed with FAAS. The synthesized sorbent was evaluated for its surface property, functional group and surface morphology by Zeta potential, Fourier transform infrared spectrophotometer (FTIR), and scanning electron microscope (SEM), respectively. The relevant measurement parameters, such as pH, extraction time, type and concentration of eluent, sample volume and reusability, were optimized. Under the optimal conditions, preconcentration factor was 13.33. The limit of detection (LOD) and limit of quantitation (LOQ) obtained were 0.070 and 0.23 mg/L, respectively. The relative standard deviation (%RSD) was 3.41%. Recovery values were 90.1 - 123%. In addition, the robustness of the method was affirmed in terms of tolerance limit obtained from interference studies.

Microextraction Techniques with Deep Eutectic Solvents

In this review, the ever-increasing use of deep eutectic solvents (DES) in microextraction techniques will be discussed, focusing on the reasons needed to replace conventional extraction techniques with greener approaches that follow the principles of green analytical chemistry. The properties of DES will be discussed, pinpointing their exceptional performance and analytical parameters, justifying their current extensive scientific interest. Finally, a variety of applications for commonly used microextraction techniques will be reported.

Selenium functionalized magnetic nanocomposite as an effective mercury (II) ion scavenger from environmental water and industrial wastewater samples

A novel core-shell magnetic-selenium nanocomposite (Fe₃O₄@SiO₂@Se) was synthesized for fast and effective removal of Hg (II) ions from various industrial and environmental water samples. The composition, property, and structure of Fe₃O₄@SiO₂@Se were characterized by spectral and microscopic techniques. The key parameters affecting the removal were evaluated and optimized. The concentration of residual Hg (II) ions in the solution was measured using a cold vapor atomic absorption spectrometer. At pH = 3.0, Fe₃O₄@SiO₂@Se was capable to remove Hg (II) ions ranged from 100 μg L^-1 to 10 mg L^-1 within 20 min with the efficiency of approximately 99% in a way that residual concentration levels matched international standards. This level of removal efficiency was well maintained up to salinity of 25 g L^-1. Kinetic investigations revealed compliance with a second-order kinetic model. The linear regression coefficient suggested the adsorption of Hg (II) ions by the adsorbent followed the Langmuir isotherm model (R² > 0.997). The maximum capacity of the adsorbent obtained through investigating the isotherms was 70.42 mg g^-1. The Fe₃O₄@SiO₂@Se adsorbent effectively removed the Hg (II) ions spiked to different samples, including tap water, river water, seawater, and industrial wastewater. Therefore, this nano-adsorbent can be used as a good alternative for Hg (II) removal, in practical applications.

Poly (deep eutectic solvents) as a new class of sustainable sorbents for solid phase extraction: application for preconcentration of Pb (II) from food and water samples

A new class of polymeric sorbents based on deep eutectic solvents (DESs) is introduced. These materials are obtained from simple and inexpensive precursors via an energy-efficient process. The primary benefit of these sorbents is that they possess the unique characteristics of DESs and porous materials simultaneously. Moreover, the possibility of tailoring deep eutectic solvents allows designing a specific polymer for a desired analyte, based on its physical and chemical properties. In this work, the deep eutectic solvent of tetrabutylammonium bromide and acrylic acid (1:2 molar ratio) was prepared and then polymerized under solventless condition. The synthesized polymer was characterized by FT-IR spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), and Brunauer, Emmett and Teller analysis (BET) to evaluate the properties of the sorbent. The poly (TBAB-2AA DES) was applied as a selective sorbent for preconcentration of lead from food and water samples prior to its quantification by flame atomic absorption spectroscopy (FAAS). Variable factors affecting the extraction were optimized, and under the optimum conditions, the calibration plot was linear in the range 5.0-250.0 μg L^-1. The relative standard deviation was (for n = 5) (RSD) < 3%. The limit of detection (LOD) and the enhancement factor were found to be 2.0 μg L^-1 and 50, respectively. Finally, the accuracy of the method was assessed by comparison of the results with those obtained by direct determination of lead using inductively coupled plasma mass spectrometry (ICP-MS) and spiked real samples. The obtained recoveries were between 92 and 106%. Graphical abstract.

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.

A new magnetized thermophilic bacteria to preconcentrate uranium and thorium from environmental samples through magnetic solid-phase extraction

A magnetic solid-phase extraction (MSPE) method was developed for simultaneous preconcentrations of U(VI) and Th(IV) before their measurements by inductively coupled plasma optical emission spectrometry (ICP-OES). The main idea of this biotechnological application depends on the use of bacteria, thermophilic Bacillus cereus SO-14, as a solid-phase biosorbent. It was immobilized to γ-Fe₂O₃ magnetic nanoparticles and used for MSPE. Characterization of the biosorbent was performed using the scanning electron microscope (SEM), the energy dispersive X-ray (EDX) and Fourier transform infrared (FT-IR) spectroscopy. Also, the the best conditions of experimental parameters were examined, and the reliability of the method developed was verified by applying the certified reference materials. Limit of detections (LODs) of the U(VI) and Th(IV) was calculated as 0.008 and 0.013 ng mL^-1 respectively. Relative standard deviations (RSDs) were found to be 1.6 and 2.4 %, respectively, for U(VI) and Th(IV). R² was also calculated as 0.9991. Preconcentration factors were achieved as 100 for both elements. It should be highlighted that LODs were critically improved and the sensitivity of ICP-OES was enhanced.

New guidelines for testing "Deep eutectic solvents" toxicity and their effects on the environment and living beings

Deep eutectic solvents (DESs) were described at the beginning of this century as an alternative to ionic liquids (ILs) in green chemistry. Despite their obvious sustainable advantages as reaction media, there is still controversy about their potential toxicity. Most of the ecotoxicity assays done up to now involving DESs are based on antibiograms. This is not a good approach due to the high density and viscosity of most DESs already described. Additionally, antibiograms do not allow continuous monitoring of neither cellular growth nor changes on physicochemical parameters like culture acidification due to cellular growth or DESs metabolization. This work starts by displaying advantages and disadvantages of the DESs toxicity assays already reported. Then, using a new DES recently described and Escherichia coli as a model microorganism, liquid cultures with continuous monitoring of pH, temperature, shaking and optical density have been used, for the first time, to quantify potential toxicity of the DES as well as the degree of the cellular tolerance (in preadapted and non-preadapted cells). The results obtained show that this new DES is not toxic for E. coli at concentrations up to 300 mM and cellular preadaptation was crucial for the cells to grow. At concentrations between 300 mM and 450 mM, cells can tolerate this DES. Above 600 mM, the DES is toxic causing complete inhibition of growth. This toxicity is not only due to the chemical composition of the DES, but also due to the high acidification of the media caused by the DES hydrolysis during cellular growth. The consequences of sterilization procedures on the DES stability are also analysed into detail, finding that sterilization by autoclave promotes DES hydrolysis. From these results, new guidelines are proposed for furthers studies aiming to characterize and quantify DESs toxicity.

Removal of heavy metals in aquatic environment by graphene oxide composites: a review

As the most important graphene derivate, graphene oxide (GO) is a high-efficient adsorbent for the removal of heavy metals in aquatic environment due to its abundant oxygen functional groups, enormous specific area, and strong hydrophilia. However, there are some drawbacks, such as easily aggregating and difficult separation, restricting the environmental application of GO. GO is not a suitable adsorbent by itself. Hence, some materials were used to synthesize GO composites, and GO composites are commonly characterized by high adsorption capacity to overcome the above drawbacks. This review discusses five main GO composites-GO-chitosan, GO-alginate, GO-SiO₂, NZVI-rGO, and magnetic GO composites-and summarizes the synthesis methods of GO composites and its application for the removal of heavy metals in aquatic environments. The influencing factors, adsorption capacities, and mechanisms related to the removal of heavy metals by GO composites are highlighted. Lastly, the application potentials and challenges of GO composites for aqueous environmental remediation are discussed. Graphical abstract.

Remediation of mercury contaminated soil, water, and air: A review of emerging materials and innovative technologies

Mercury contamination in soil, water and air is associated with potential toxicity to humans and ecosystems. Industrial activities such as coal combustion have led to increased mercury (Hg) concentrations in different environmental media. This review critically evaluates recent developments in technological approaches for the remediation of Hg contaminated soil, water and air, with a focus on emerging materials and innovative technologies. Extensive research on various nanomaterials, such as carbon nanotubes (CNTs), nanosheets and magnetic nanocomposites, for mercury removal are investigated. This paper also examines other emerging materials and their characteristics, including graphene, biochar, metal organic frameworks (MOFs), covalent organic frameworks (COFs), layered double hydroxides (LDHs) as well as other materials such as clay minerals and manganese oxides. Based on approaches including adsorption/desorption, oxidation/reduction and stabilization/containment, the performances of innovative technologies with the aid of these materials were examined. In addition, technologies involving organisms, such as phytoremediation, algae-based mercury removal, microbial reduction and constructed wetlands, were also reviewed, and the role of organisms, especially microorganisms, in these techniques are illustrated.

Preparation of magnetic core-shell Fe3O4@polyaniline composite material and its application in adsorption and removal of tetrabromobisphenol A and decabromodiphenyl ether

Present study described a magnetic adsorption and removal method with prepared magnetic core-shell Fe₃O₄@polyaniline microspheres for the removal of two typical BFRs, tetrabromobisphenol-A (TBBPA) and decabromodiphenyl ether (BDE-209) from water samples. Magnetic core-shell Fe₃O₄@polyaniline microspheres were prepared by a hydrothermal and two step polymerization method with cheap iron salts and aniline, which were characterized with transmission electron microscopic (TEM) and scanning electron microscopy (SEM). The results showed that the Fe₃O₄@polyaniline microspheres earned a clear thickness shell of polyaniline (about 50 nm) and a saturation magnetization of 40.4 emu g^-1. The Magnetic core-shell Fe₃O₄@polyaniline exhibited excellent adsorption capability and removal rate to TBBPA and BDE 209. The adsorption of TBBPA and BDE 209 all followed pseudo-second order kinetics and agreed well to the Freundlich adsorption isotherms model. The negative Gibbs free energy change (ΔG⁰) and positive standard enthalpy change (ΔH⁰) for TBBPA and BDE-209 suggested that the adsorption was spontaneous and endothermic in nature. These results demonstrated that Fe₃O₄@PANI was a good adsorbent and would have a good application prospect in the removal of pollutants from environmental water.

A novel bimacrocyclic polyamine-based fluorescent probe for sensitive detection of Hg2+ and glutathione in human serum

Detection of glutathione in human serum is of great importance for clinical diagnosis of various diseases, such as AIDS, diabetes mellitus, Alzheimer disease and cancer. In this work, a new water-soluble bismacrocyclic polyamine-derived compound, namely L, which contains two molecules of 4-nitro-1,2,3-benzoxa-diazole as the fluorophores, was designed and prepared. The experiments of selectivity of L toward metal ions showed it could rapidly and sensitively detect Hg²⁺ with a detection limit of 27 nM. Furthermore, the cell imaging and co-staining experiments in HeLa cells demonstrated that the L-Hg²⁺ probe had selectivity for the Golgi apparatus to a certain degree. Moreover, it had excellent selectivity for biothiols, especially for glutathione. Finally, the probe was successfully applied to sensitively detect glutathione (GSH) in human serum and fetal bovine serum.

Metal affinity-carboxymethyl cellulose functionalized magnetic graphene composite for highly selective isolation of histidine-rich proteins

A metal affinity-carboxymethyl cellulose functionalized magnetic graphene, namely MGCI-Cu composite, was prepared by successive modifications of graphene oxide nanosheets with magnetic nanoparticles, carboxymethyl cellulose (CMC), iminodiacetic acid (IDA) and then chelated with copper ions. The successful modifications of the graphene surface were demonstrated by various characterizations, and a high density of 6.17 μmol m^-2 for metal affinity groups was obtained. The composite exhibited high adsorption selectivity toward histidine-rich proteins. The adsorption was governed by strong metal affinity binding force between hisitidine residues of proteins and immobilized Cu²⁺ ions of MGCI-Cu composite. In particular, highly selective isolation of hemoglobin (Hb) was achieved in 0.2 mol L^-1 phosphate buffer at pH 8. The adsorption capacity of Hb significantly increased to 769 mg g^-1 in comparison to that of 435 mg g^-1 on metal affinity modified magnetic graphene composite (MGI-Cu) without CMC modification. The adsorbed Hb molecules were recovered with a carbonate buffer (0.2 mol L^-1 pH 10) containing 0.5 mol L^-1 imidazole. MGCI-Cu composite displayed favorable reusability for at least four times after regeneration of the composite by edetic acid (EDTA) and Cu²⁺ solution. The practical applications demonstrated that MGCI-Cu composite could highly selectively isolate Hb from human whole blood and polyhistidine-tagged recombinant protein from Escherichia coli (E. coli) lysate.