Magnetic solid-phase extraction based on Fe3O4/graphene oxide nanoparticles for the determination of malachite green and crystal violet in environmental water samples by HPLC

This work describes a magnetic Fe₃O₄/graphene oxide (GO)-based solid-phase extraction (MSPE) technique for high performance liquid chromatography (HPLC) detection of malachite green (MG) and crystal violet (CV) in environmental water samples. Fe₃O₄/ GO magnetic nanoparticles were synthesised by a chemical co-precipitation method and characterised by scanning electron micrograph, transmission electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and surface area analyser. The prepared Fe₃O₄/GO magnetic nanoparticles were used as the adsorbents of MSPE for MG and CV. By coupling with HPLC, a sensitive and cost-effective method for simultaneous determination of MG and CV was developed. The important parameters including the amount of Fe₃O₄/GO, pH of the sample solution, extraction time, salt effect, the type and volume of desorption solvent were investigated in detail. Under optimised conditions, the calibration curves were linear in the concentration range of 0.5–200 μg L^?1, and the limits of detection were 0.091 and 0.12 μg L^?1 for MG and CV, respectively. Finally, the established MSPE-HPLC method was successfully applied to determine MG and CV in environmental water samples with the recoveries ranging from 91.5% to116.7%.     

Synthesis and application of polythiophene-coated Fe3O4 nanoparticles for preconcentration of ultra-trace levels of cadmium in different real samples followed by electrothermal atomic absorption spectrometry

In this research, magnetic Fe₃O₄ nanoparticles were synthesised by co-precipitation method and modified with polythiophene (PT) to produce Fe₃O₄-PT nanoparticles for preconcentration and determination of cadmium (??) ion followed by electrothermal atomic absorption spectrometry. The results of FT-IR spectroscopy, EDX analysis and SEM images show that Fe₃O₄-PT nanoparticles were synthesised successfully. Different parameters such as sample pH, amounts of adsorbent, sample volume, extraction time, type and concentration of eluent and desorption time were completely investigated and optimum conditions were selected.

Under the optimum conditions, the calibration curve was linear in the range of 0.01–0.25 µg L^?1 of cadmium (??). The relative standard deviation was 4.7% (n = 7, 0.10 µg L^?1 Cd²⁺) and limit of detection was 3.30 ng L^?1. The accuracy of the proposed method was verified by the analysis of a certified reference material and spike method. Finally, the proposed method was applied for the determination of ultra-trace levels of cadmium (??) in different water and food samples.     

Simultaneous Analysis of Organophosphorus Pesticides in Water by Magnetic Solid-Phase Extraction Coupled with GC–MS

Magnetic solid-phase extraction (MSPE) coupled with gas chromatography–mass spectrometry was applied for the analysis of organophosphorus pesticides (OPPs) in water samples. We chose C18-functionalized Fe₃O₄@mSiO₂ microspheres as the magnetic sorbents to extract and enrich OPPs from water samples with the advantages of good solubility in water, large surface area and fast separation ability. In this study, six kinds of OPPs were analyzed and various parameters of MSPE procedure, including eluting solvent, the amount of magnetic absorbents and extraction time were optimized. Validation experiments showed that the optimized method had good linearity with correlation coefficients r ² > 0.98 and satisfactory precision with the relative standard deviation ≤10.7 %. The limits of detection were 1.8–5.0 μg L^?1 and the limits of quantification ranged from 6.1 to 16.7 μg L^?1. We concluded that the proposed method was successfully applied to analyze OPPs in real water samples and the results indicated that it had the advantages of simplicity, convenience and efficiency.     

Trace analysis of Pt (IV) metal ions in roadside soil and water samples by Fe3O4/graphene/polypyrrole nanocomposite as a solid-phase extraction sorbent followed by atomic absorption spectrometry

A novel Fe₃O₄/graphene/polypyrrole nanocomposite has been successfully synthesised via a simple chemical method and applied as a new magnetic solid-phase extraction (MSPE) sorbent for the separation and pre-concentration of trace amounts of Pt (IV) in environmental samples followed by flame atomic absorption spectrometric (FAAS) detection. The nanocomposite has been characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. Seven important parameters, affecting the extraction efficiency of Pt (IV), including pH, adsorption time, desorption solvent type and concentration, desorption time, elution volume and sample volume, were investigated. Under the optimised conditions, the calibration graph was linear in the range of 50–1500 μg L^?1 (R = 0.993). The detection limit and pre-concentration factor (PF) for Pt (IV) were found to be 16 μg L^?1 and 112.5, respectively. Under the optimised solid-phase extraction (SPE) conditions, the adsorption isotherm and the adsorption capacity of the nanocomposite for Pt (IV) were studied. Pt (IV) adsorption equilibrium data were fitted well to the Langmuir isotherm and the maximum adsorption capacity of the magnetic sorbent was calculated from the Langmuir isotherm model as 416.7 mg g^?1. The precision of the method was studied as intraday and interday variations. A relative standard deviation percentage (RSD%) value less than 3.0 indicates that the method is precise. Also, the accuracy of the method was tested by the analysis of the standard reference material (NIST SRM 2556) and by recovery measurements on spiked real samples. It was also shown that the optimised method was suitable for the analysis of trace amounts of Pt (IV) in roadside soil, tap water and wastewater samples.     

Reprint of: Extraction of fluoxetine from aquatic and urine samples using sodium dodecyl sulfate-coated iron oxide magnetic nanoparticles followed by spectrofluorimetric determination

A new method based on the combination of magnetic solid phase extraction (MSPE) and spectrofluorimetric determination was developed for isolation and preconcentration of fluoxetine form aquatic and biological samples using sodium dodecyl sulfate (SDS) coated Fe₃O₄ nanoparticles (NPs) as a sorbent. The unique properties of Fe₃O₄ NPs including high surface area and strong magnetism were utilized effectively in the MSPE process. Effect of different parameters influencing the extraction efficiency of fluoxetine including the amount of Fe₃O₄ and SDS, pH value, sample volume, extraction time, desorption solvent and time were optimized. Under optimized condition, the method was successfully applied to the extraction of fluoxetine from water and urine samples and absolute recovery amount of 85%, detection limit of 20 μg L⁻¹ and a relative standard deviation (RSD) of 1.4% were obtained. The method linear response was over a range of 50–1000 μg L⁻¹ with R² = 0.9968. The relative recovery in different aquatic and urine matrices were investigated and values of 80% to 104% were obtained. The whole procedure showed to be conveniently fast, efficient and economical for extraction of fluoxetine from environmental and biological samples.     

Preparation of carbon coated Fe3O4 nanoparticles and their application for solid-phase extraction of polycyclic aromatic hydrocarbons from environmental water samples

The carbon coated Fe₃O₄ nanoparticles (Fe₃O₄/C) were synthesized by a simple hydrothermal reaction and applied as solid-phase extraction (SPE) sorbents to extract trace polycyclic aromatic hydrocarbons (PAHs) from environmental water samples. The Fe₃O₄/C sorbents possess high adsorption capacity and extraction efficiency due to strong adsorption ability of carbon materials and large surface area of nanoparticles, and only 50 mg of sorbents are required to extract PAHs from 1000 mL water samples. The adsorption attains equilibrium rapidly and analytes are eluted with acetonitrile readily. Salinity and solution pH have no obvious effect on the recoveries of PAHs, which avoids fussy adjustment to water sample before extraction. Under optimized conditions, the detection limits of PAHs are in the range of 0.2–0.6 ng L⁻¹. The accuracy of the method was evaluated by the recoveries of spiked samples. Good recoveries (76–110%) with low relative standard deviations from 0.8% to 9.7% are achieved. This new SPE method provides several advantages, such as high extraction efficiency, high breakthrough volumes, convenient extraction procedure, and short analysis times. To our knowledge, this is the first time that Fe₃O₄/C nanoparticles are used for the pretreatment of environmental water samples.     

Determination of Hydrogen Peroxide Using a Novel Sensor Based on Fe3O4 Magnetic Nanoparticles

Fe₃O₄ magnetic nanoparticles were synthesized by chemical co-precipitation with sodium citrate as a surfactant and were used with chitosan to construct a novel hydrogen peroxide sensor. The electrochemical behavior of hydrogen peroxide at the sensor was investigated by cyclic voltammetry. The composite film electrocatalyzed the reduction of hydrogen peroxide, and the peak current increased linearly with concentration from 1.00 × 10^?5 to 1.00 × 10^?3 mol · L^?1 (R = 0.9974) with a detection limit of 1.53 × 10^?6 mol · L^?1. This novel nonenzyme sensor provided good sensitivity, stability, and precision with potential applications.     

Nanoparticles of type Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-SiO<Subscript>2</Subscript>-graphene oxide and coated with an amino acid-derived ionic liquid for extraction of Al(III), Cr(III), Cu(II), Pb(II) prior to their determination by ICP-OES

An amino acid derived ionic liquid, Fe₃O₄ nanoparticles and graphene oxide (GO) were used to prepare a material for the magnetic solid phase extraction (MSPE) of the ions Al(III), Cr(III), Cu(II) and Pb(II). The material was characterized by Fourier transform infrared spectral (FT-IR), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), magnetic analysis and isoelectric point (pI) analysis. It is shown to be a viable sorbent for the separation of these metal ions. Single factor experiments were carried out to optimize adsorption including pH values, ionic strength, temperature and solution volume. Following desorption with 0.1 M HCl, the ions were quantified by inductively coupled plasma optical emission spectrometry. Under the optimum conditions, the method provides a linear range from 10 to 170 μg· L^?1 for Al(III); from 4.0 to 200 μg· L^?1 for Cr(III); from 5.0 to 170 μg· L^?1 for Cu(II); and from 5.0 to 200 μg· L^?1 for Pb(II). The limits of detection (LOD) are 6.2 ng L^?1 for Al(III); 1.6 ng L^?1 for Cr(III); 0.52 ng L^?1 for Cu(II); and 30 ng L^?1 for Pb(II). Method performance was investigated by determination of these ions in (spiked) environmental water and gave recoveries in the range of 89.1%–117.8%.

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Graphical abstract The graph shows that Al(III), Cr(III), Cu(II), Pb(II) are not adsorbed quantitatively by Fe₃O₄-SiO₂. On the other hand, Cr(III) and Pb(II) are adsorbed quantitatively by Fe₃O₄-SiO₂-GO while Al(III) and Cu(II) are not quantitatively retained. However, 3D–Fe₃O₄-SiO₂-GO-AAIL adsorb all these 4 metal ions quantitatively.

     

Synthesis of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@PPy–MWCNT nanocomposite and its application for extraction of ultra-trace amounts of PAHs from various samples

In the present study, multi-walled carbon nanotube oxide was immobilized on the pyrrole magnetic nanoparticles. Application of the synthesized material was investigated for the magnetic solid-phase extraction (MSPE) of polycyclic aromatic hydrocarbons (PAHs), from the environmental samples. Determinations of the analytes were performed with gas chromatography–mass spectrometry. The structure and morphology of Fe₃O₄@PPy–MWCNT were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermal gravimetric analysis, and vibrating sample magnetometer. Performance of MSPE is mainly affected by extraction time, sorbent amount, sample solution volume, and eluent type and volume. In this study, the best possible performance of MSPE has been achieved using a combination of central composite design and Bayesian regularized artificial neural network technique. Under the optimum extraction conditions, linear range between 0.5 and 250 µg L^?1 (R ² > 0.994), preconcentration factors from 232 to 403 and limits of detection ranging from 0.1 to 0.3 µg L^?1 were obtained. Relative standard deviations for intra-day and inter-day precision were 3.3–5.1% and 3.7–5.6%, respectively. In addition, feasibility of the method was demonstrated by extraction and determination of PAHs from some real samples containing tap water, hookah water as well as soil samples, and relative recovery in the range of 85.4–106.8% was obtained. This MSPE method provides several advantages, such as high extraction efficiency, minimum sorbent for extraction of the analytes from high sample volumes, convenient extraction procedure, and short analysis times.     

Determination of Tetracycline in Water and Honey by Iron(II,III)/Aptamer-Based Magnetic Solid-Phase Extraction with High-Performance Liquid Chromatography Analysis

A novel aptamer-based adsorbent was prepared for the magnetic solid-phase extraction of tetracycline. The Fe₃O₄/aptamer adsorbent was fabricated by immobilizing an aptamer on the surface of Fe₃O₄ magnetic nanoparticles by the reaction between avidin and biotin. The parameters affecting the isolation efficiency such as the pH, extraction time, extraction temperature, eluent, and elution time were investigated in detail. Under the optimal conditions, a linear relationship between the peak area and the concentration of tetracycline was observed in the range from 10.0 to 3000.0?µg L^?1 with a correlation coefficient of 0.9985 and a limit of detection of 2.5?µg L^?1. The developed method was successfully employed for the determination of tetracycline in honey and water samples with recovery values from 82.9 to 107.3% and relative standard deviations less than 7.6%. Compared with previously reported methods for the determination of tetracycline, the proposed protocol provides improvements in the limit of detection and specificity with reduced consumption of adsorbent and organic solvents.     

A rapid microwave-assisted acid extraction method based on the use of diluted HNO3-H2O2 followed by ICP-MS analysis for simultaneous determination of trace elements in coal samples

Before coal processing such as pyrolysis, liquefaction, gasification and combustion, it is very crucial to monitor the trace element concentration levels as that determines the coal quality. Therefore, the current study describes the development of microwave-assisted acid extraction (MW-AAE) method for extraction of 15 trace elements in coal samples prior to their determination using inductively coupled plasma-mass spectrometry. Diluted HNO₃-H₂O₂ was used in order to reduce reagents amount used, eliminate matrix interferences caused by concentrated acids and to decrease waste produced in analytical laboratories. The optimisation of the proposed extraction method was carried out by using a full factorial design (2⁴) involving four factors; that is, temperature, extraction time, HNO₃ and H₂O₂ concentrations. The optimum conditions for the MW-AAE procedure were found to be 200°C, 5 min, 5 mol L^?1 and 2 mol L^?1 for temperature, extraction time, HNO₃ and H₂O₂ concentrations, respectively. Under optimum conditions, the accuracy of the MW-AAE method was examined by analysing three coal certified reference materials (SARM 18, 19 and 20) and recoveries of 80–115% were achieved for V, Mn, Co, Ni, Cu, Zn, Ga, Ge, As, Sr, Zr, Cs, Ba, Pb and U, except for Ti (10–25%) and Hf (27–70%). In addition, the precision of the proposed method, expressed in terms of relative standard deviation (SD) (n = 15), was within the accepted range (≤3.5%). The method detection limits of 0.001–0.57 µg g^?1 for all trace elements under the investigation were similar to the literature reported work, except for Ti (4.00 µg g^?1).     

Polythionine-decorated magnetic nanoparticles as a robust and highly effective sorbent for mercury determination in environmental water samples

Extraction, pre-concentration and determination of trace amounts of mercury ions from water samples were investigated by magnetic solid phase extraction (MSPE) method using Fe₃O₄ nanoparticles decorated with polythionine as an adsorbent. A simple chemical synthesis by catalytic reaction of thionine in the presence of FeCl₃ and hydrogen peroxide was used for preparation of the magnetic sorbent. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, vibrating sample magnetometer analysis and Fourier transform infrared spectroscopy were used to characterise the adsorbent. Mercury ions were determined by cold vapour atomic absorption spectrometry. The parameters for MSPE procedure, such as pH of the extraction solution, adsorption time, weight adsorbent, elution conditions (type, concentration and volume of the eluent), volume of the sample solution and effects of coexisting ions were investigated. The obtained optimal conditions were: sample pH of 4; sorbent amount of 4 mg; sorption time of 20 min; elution solvent of HNO₃ (0.3 mol L^?1)/thiourea (2% w/v) with volume of 2 mL, and breakthrough volume of 400 mL. A good linearity in the concentration range of 0.025–40 µg L^?1 (R² > 0.999) with the pre-concentration factor of 198 was obtained. The limits of detection and quantification were achieved as 0.008 and 0.025 µg L^?1, respectively. Furthermore, sea and river water samples were analysed and good recoveries (97.1–99.6%) were obtained.     

The fabrication of a nanoscale polyoxometalate based magnetic adsorbent and its selective adsorption on cationic dyes

Amino group-functionalized Fe₃O₄ is loaded on a coordination complex-modified polyoxometalate nanoparticle. In this composite material, Fe₃O₄ and coordination complex-modified polyoxometalate are connected with intense hydrogen bonds as suggested by FTIR. This composite material exhibits excellent methylene blue (MB) adsorption, with adsorption capacity of 175.5 mg g^?1. It also possesses selective separation ability between cationic and anionic dye molecules. In binary solution of MB and methyl orange (MO), MB adsorption efficiency reaches 75%, but it exhibits almost no effect on the adsorption of methyl orange. The saturation magnetization value of this composite material is 18.89 emu g^?1, allowing magnetic separation, which facilitates the recycle and reuse of this composite adsorbent.     

Magnetic titanium oxide nanoparticles for hemimicelle extraction and HPLC determination of organophosphorus pesticides in environmental water

We report on a method for the extraction of organophosphorus pesticides (OPPs) from water samples using mixed hemimicelles and magnetic titanium dioxide nanoparticles (Fe₃O₄@TiO₂) modified by cetyltrimethylammonium. Fe₃O₄@TiO₂ nanoparticles were synthesized by a hydrothermal process and then characterized by scanning electron microscopy and Fourier transform IR spectrometry. The effects of the quantity of surfactant, extraction time, desorption solvent, pH value, extraction volume and reuse of the sorbent were optimized with respect to the extraction of OPPs including chlorpyrifos, dimethoate, and trichlorfon. The extraction method was applied to analyze OPPs in environmental water using HPLC along with UV detection. The method has a wide linear range (100–15,000 ng L^?1), good linearity (r?>?0.999), and low detection limits (26–30 ng L^?1). The enrichment factor is ~1,000. The recoveries (at spiked levels of 100, 1,000 and 10,000 ng L^?1) are in the range of 88.5–96.7 %, and the relative standard deviations range from 2.4 % to 8.7 %.

Development of graphene-carbon nanotube-coated magnetic nanocomposite as an efficient sorbent for HPLC determination of organophosphorus pesticides in environmental water samples

A magnetic solid-phase extraction (MSPE) method coupled to high performance liquid chromatography with UV (HPLC-UV) was proposed for the determination of organophosphorus pesticides (OPPs) at trace levels in environmental water samples. The ternary nanocomposite of graphene-carbon nanotube-Fe₃O₄ (G-CNT-Fe₃O₄) has been synthesised via a simple solvothermal process and the resultant material was characterised by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Significant factors that affect the extraction efficiency, such as amount of magnetic nanocomposite, extraction time, ionic strength, solution pH and desorption conditions were carefully investigated. The results demonstrated that the proposed method had a wide dynamic linear range (0.005–200 ng mL^?1), good linearity (R² = 0.9955–0.9996) and low detection limits (1.4–11 pg mL^?1). High enrichment factors were achieved ranging from 930 to 1510. The results show that the developed method is suitable for trace level monitoring of OPPs in environmental water samples.     

Adsorption of asphaltene from crude oil by applying polythiophene coating on Fe3O4 nanoparticles

The objective of the present study was to investigate the potential use of applying polythiophene coating on magnetic Fe₃O₄ nanoparticles for the enhancement of asphaltene adsorption. Two stages of experimental were conducted. In the first stage, the ability of coated nanoparticles for asphaltene adsorption in synthetic asphaltene-toluene solution was evaluated. The effects of parameters such as nanoparticles concentration, initial concentration of asphaltene, and temperature were studied. In the second stage, the performance of the coated nanoparticles for the adsorption of asphaltene from crude oil was investigated under atmospheric pressure and a pressure-volume-temperature (PVT) apparatus was utilized for simulated reservoir conditions. Fe₃O₄ and Fe₃O₄-PT MNPs were synthesized using an effective co-precipitation method. The results of the first-stage tests indicated that the maximum adsorption capacity values for Fe₃O₄ and Fe₃O₄-PT MNPs were 0.79 and 1.09?mg?m^?2, respectively. The optimum value of nanoparticles concentration was approximately determined as 10?g?L^?1. According to the adsorption isotherms and kinetics, the Langmuir and pseudo-second-order Lagergren models were consistent with the experimental data, respectively. The average adsorption efficiencies for Fe₃O₄-PT and Fe₃O₄ MNPs were 78.98 and 65.94%, respectively. The results of the performed experiments on crude oil showed that Fe₃O₄-PT MNPs could adsorb asphaltenes from crude oil in a similar trend as synthetic asphaltene-toluene solution.     

MultiSimplex optimization of the dispersive solid-phase microextraction and determination of fenitrothion by magnetic molecularly imprinted polymer and high-performance liquid chromatography

A magnetic molecularly imprinted polymer (MMIP) was fabricated and used as the sorbent for the MMIP-dispersive solid-phase microextraction of fenitrothion prior its determination by high-performance liquid chromatography equipped with an ultraviolet detector. The MMIP was prepared using functionalized Fe₃O₄ nanoparticles as the magnetic supporter. Methacrylic acid, ethylene glycol dimethacrylate and fenitrothion were used as the functional monomer, the cross-linker and the template, respectively. The properties of the resultant MMIP were evaluated using X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. The sorbent exhibited high selectivity and affinity toward fenitrothion compared to other organophosphate pesticides with the maximum adsorption capacity of 31.5 mg g^?1. The effective variables on the extraction were optimized by univariable and MultiSimplex methods. The calibration curve exhibited linearity over the concentration range of 0.3–50.0 μg L^?1 with the limit of detection of 0.1 μg L^?1. The relative standard deviations at 10.0 μg L^?1 level of FNT (n = 5) for intra- and inter-day assays were 1.6 and 3.1%, respectively. The proposed method was successfully used for the determination of trace amounts of FNT in food and water samples.     

Optimized solid phase extraction based on diethyldithiocarbamate-coated Fe3O4 magnetic nanoparticles followed by ICP-OES for determination of Cd(II) and Ni(II) in rice and water samples

In the present study, application of Fe₃O₄ magnetic nanoparticles (MNPs) coated with diethyldithiocarbamate as a solid-phase sorbent for extraction of trace amounts of cadmium (Cd²⁺) and nickel (Ni²⁺) ions by the aid of ultrasound was investigated. The analytes were determined by inductively coupled plasma-optical emission spectroscopy. Fe₃O₄ MNPs were prepared by solvothermal method and characterized with dynamic light scattering, scanning electron microscope and X-ray diffraction. Response surface methodology was used for optimization of the extraction process and modeling the data. The optimal conditions obtained were as follows: chelating agent, 1.2 g L^?1; pH, 6.13; sonication time, 13 min and Fe₃O₄ MNPs, 10.3 mg. The calibration curves were linear over the concentration range of 1–1,000 μg L^?1 for Cd²⁺ and 2.5–1,000 for Ni²⁺ with the determination coefficients (R ²) of 0.9997 and 0.9995, respectively. The limits of detection were 0.27 μg L^?1 for Cd²⁺ and 0.76 μg L^?1 for Ni²⁺. The relative standard deviations (n = 7, C = 200 μg L^?1) for determination of Cd²⁺ and Ni²⁺ were 2.0 and 2.7 %, respectively. The relative recoveries of the analytes from tap, river and lagoon waters and rice samples at the spiking level of 10 μg L^?1 were obtained in the range of 95–105 %.     

Efficient separation of nitrite from aqueous solutions by grafting metalloporphyrin on Fe3O4 nanoparticles

A new sorbent comprising 3-aminopropyltriethoxy-silane-coated magnetic nanoparticles functionalized with organic moieties containing the cobalt(III) porphyrin complex Co (TCPP) [TCPP: 4,4′,4″,4″′-(21H,23H-porphine-5,10,15,20-tetrayl)tetrakis (benzoic acid)], was prepared, for nitrite removal from drinking water. Fe₃O₄ nanoparticles were synthesized by co-precipitation of Fe²⁺ and Fe³⁺, then surface of the Fe₃O₄ nanoparticles was modified with APTES and Co (TCPP). The sorbent was characterized using FTIR, TGA, XRD, SEM and TEM analysis. The batch experiments showed that the proposed sorbent can effectively be used to remove nitrite from water. Various parameters such as pH of the solution, contact time, sorbent dosage, concentration of desorbing reagent, and influence of other interfering anions have been investigated. Under optimal conditions for a nitrite concentration of 10 mg L^?1 (i.e., contact time 15 min, pH 5.5 and nanosorbents dosage 100 mg), the percentage of the extracted nitrite ions was 92.0. Nitrite sorbing material was regenerated with 10 mM NaOH up to 97.0 %. The regeneration studies also showed that nanosorbents are regenerable and can be used for a couple of times.     

Magnetic solid-phase extraction of malachite green using soluble eggshell membrane protein doped with magnetic graphene oxide nanocomposite

ABSTRACT

This study describes a new magnetic solid-phase extraction (MSPE) technique based on Fe₃O₄/graphene oxide-soluble eggshell membrane protein (Fe₃O₄/GO-SEP) for accurate measurement of malachite green (MG) residue in various water samples residues by UV-Vis spectroscopy. The morphology of the prepared adsorbent has been studied by scanning electron microscopy and atomic force microscopy in details. Parameters affecting the MSPE were optimised and determined with UV-Vis spectrophotometry thoroughly. Under the optimised extraction circumstances, the introduced method represented a wide linearity over the concentration of 0.5–250 ng mL^?1, a high enrichment factor of 83.3 and low detection limit of 0.2 ng mL^?1. The prepared Fe₃O₄/GO-SEP was successfully used for preconcentration and determination of MG in river and fish farming water samples with suitable precision and accuracy.