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.     

Magnetic nanofibrous polyaniline nanocomposite for solid-phase extraction of naproxen from biological samples prior to its spectrofluorimetric determination

Nanofibrous polyaniline–magnetite (PANI/Fe₃O₄) nanocomposite was in situ prepared through adsorption of magnetite nanoparticles onto PANI nanofibers surface and utilized as an efficient sorbent for magnetic solid-phase extraction of naproxen from water and biological samples, followed a desorption step and spectrofluorimetric determination. Field-emission scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, thermal gravimetric analysis and X-ray diffraction techniques were employed for characterization of the prepared nanocomposite. The important parameters influencing the extraction efficiency including PANI/Fe₃O₄ mass ratio, adsorbent dose, extraction time, sample solution pH, ionic strength, type and volume of desorption solvent and the elution time were studied and optimized. The investigated nanocomposite was successfully applied to the extraction of naproxen in spiked tap water, urine and plasma samples, with a relative recovery in the range of 90–98%. The reusability of PANI/Fe₃O₄ was examined for ten successive cycles, and the results confirm that the efficiency did not change significantly. A linear calibration plot was obtained in the range of 40–1000 ng mL^?1 with a limit of detection about 17 ng mL^?1 under the optimum conditions. The relative standard deviation (RSD) was found to be 2.34% (n = 8, concentration level of 100 ng mL^?1). The kinetics and thermodynamics of the extraction process were also studied.     

Simultaneous preconcentration and determination of malachite green and fuchsine dyes in seafood and environmental water samples using nano-alumina-based molecular imprinted polymer solid-phase extraction

Molecular imprinted polymer for determination of malachite green (MG) and fuchsine basic (FU) dyes by spectrophotometry has been used, to develop a novel simultaneous extraction and preconcentration method. Molecularly imprinted layer-coated nano-alumina (MIP@Nano-Al₂O₃) as adsorbent was prepared by surface molecular imprinting technique, and characterised by FTIR spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis (EDAX) and thermogravimetric analysis (TGA). The method is based on simultaneous extraction of MG and FU dyes from aqueous solution by using molecularly imprinted polymer and measuring the absorbance at 617 and 546 nm for MG and FU, respectively. Parameters which affect the extraction efficiency such as pH, volume of eluent and amount of adsorbent were investigated and optimised. Linear calibration curves were obtained in the range of 2–750 ng mL^?1 for MG and 1–240 ng mL^?1 for FU under optimum conditions. Detection limit based on three times the standard deviation of the blank (3S_b) was 0.655 and 0.245 ng mL^?1 (n = 10) for MG and FU, respectively. The relative standard deviation (RSD) for 100 ng mL^?1 of MG and FU was 2.35 and 3.06% (n = 7), respectively. The method was applied to the simultaneous determination of the dyes in different seafood and environmental water samples.     

Development of novel magnetic solid-phase extraction sorbent based on Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/carbon nanosphere/polypyrrole composite and their application to the enrichment of polycyclic aromatic hydrocarbons from water samples prior to GC–FID analysis

We describe a magnetic nanocomposite that consists of Fe₃O₄/carbon nanosphere/polypyrrole (Fe₃O₄/CNS/PPy). The synthesized nanocomposites were characterized by scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. The nanocomposite was successfully applied to extract of the polycyclic aromatic hydrocarbons (PAHs) from water samples. Compared to Fe₃O₄/PPy, the Fe₃O₄/CNS/PPy nanocomposite exhibits improved properties in terms of extraction. The amount of adsorbent, salt effect, extraction time, desorption time, type, and the volume of desorption solvent were optimized. Following the desorption of the extracted analytes, the PAHs (i.e., naphthalene, 2-methylnaphthalene, 2-bromonaphthalene, fluorene, and anthracene) were quantified by gas chromatography–flame ionization detector. The PAHs can be determined in 0.05–100.00 ng mL^?1 concentration range, with limits of detection (at an S/N ratio of 3) ranging from 0.01 to 0.05 ng mL^?1. The repeatability of the method was investigated with relative standard deviations of lower than 9.9% (n = 5). Also, the recoveries from spiked real water samples were in the range of 88.9–99.0%. The results indicate that the novel material can be successfully applied for the extraction and analysis of PAHs from water samples.     

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 %.

Magnetic Graphene Nanoparticles for the Preconcentration of Chloroacetanilide Herbicides from Water Samples Prior to Determination by GC-ECD

A highly sensitive method for the determination of the chloroacetanilide herbicides alachlor, acetochlor, pretilachlor, butachlor, and metolachlor in environmental water samples was developed. It is based on solid-phase extraction using magnetic graphene nanocomposite (G-Fe₃O₄) as the adsorbent, followed by gas chromatography with electron capture detection. This novel adsorbent showed a great adsorptive ability toward the analytes. The main experimental parameters such as the amount of G-Fe₃O₄, extraction time, ionic strength, the pH of the sample solution, and desorption conditions were optimized. Under the optimum conditions, the enrichment factors of the method for the analytes were in the range from 649 to 1078. A good linear response was achieved in the range of 0.2–20.0 ng mL^?1, with correlation coefficients (r) varying from 0.9964 to 0.9998. The limits of detection of the method ranged from 0.02 to 0.05 ng mL^?1 and the relative standard deviations were below 4.5%. The method was successfully applied to the determination of the herbicides in environmental water samples. Recoveries of the method for the analytes were in the range of 80.7–105.3%.     

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.     

Magnetic solid-phase extraction of imatinib and doxorubicin as cytostatic drugs by Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/graphene oxide nanocomposite

Magnetic solid-phase extraction based on Fe₃O₄/graphene oxide nanocomposites was investigated for the separation, preconcentration and determination of imatinib and doxorubicin in aqueous solutions. Synthesis of Fe₃O₄/graphene oxide was characterized by transmission electron microscopy, energy-dispersive X-ray analyzer and vibrating sample magnetometer. After optimizing the conditions, optimal experimental conditions including sample pH, the amount of the magnetic nanoparticles, the effect of salt concentration and other chemotherapy medications, eluent type and extraction time were studied and established. The method showed good linearity for the determination of doxorubicin and imatinib in the concentration range of 0.01–100 μg mL^?1 in aqueous solutions with limit of detection 1.8 ng mL^?1 for doxorubicin and 1.9 ng mL^?1 for imatinib. The relative recoveries of doxorubicin and imatinib levels were 96.7 and 88.4%, respectively. The results indicate that the present procedure is a suitable method for extraction of imatinib and doxorubicin from environmental water samples.     

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.     

Graphene oxide/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@polythionine nanocomposite as an efficient sorbent for magnetic solid-phase extraction followed by high-performance liquid chromatography for the determination of duloxetine in human plasma

Herein, an efficient graphene oxide/Fe₃O₄@polythionine (GO/Fe₃O₄/PTh) nanocomposite sorbent was introduced for magnetic solid-phase extraction combined with high-performance liquid chromatography–ultraviolet detection of duloxetine (DLX) in human plasma. To prepare the sorbent, an oxidative polymerization of thionine on the surface of magnetic GO was utilized while PTh was simply used as a surface modifier to improve extraction efficiency. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis, vibrating sample magnetometry, Fourier transform-infrared spectroscopy and Brunauer–Emmett–Teller technique were applied to characterize the prepared nanoparticles. Firstly, effective parameters controlling the performance of the extraction process were evaluated in detail and optimized. Under the optimized conditions, calibration curve showed linearity in the range of 2–2500 ng mL^?1 with regression coefficient corresponding to 0.998. Limits of detection (LOD, S/N = 3) and quantification (LOQ, S/N = 10) were 0.5 and 2 ng mL^?1, respectively. Reasonable intra-assay (3.5–4.5%, n = 6) and inter-assay (3.8–6.7%, n = 9) precision represented acceptable performance of the procedure. The applicability of the method was successfully extended to the determination of DLX in human plasma after oral administration of 60 mg single dose of the drug and finally some pharmacokinetic data was achieved.     

Magnetic solid-phase extraction of Zineb by C18-functionalised paramagnetic nanoparticles and determination by first-derivative spectrophotometry

Fe₃O₄-SiO₂-C₁₈ paramagnetic nanoparticles have been synthesised and used as magnetic solid-phase extraction (MSPE) sorbent for the extraction of Zineb from agricultural aqueous samples under ultrasonic condition and quantified through a first-derivative spectrophotometric method. The produced magnetic nanoparticles were characterised by using scanning electron microscopy, X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy and zeta potential reader. The Fe₃O₄-SiO₂-C₁₈ paramagnetic nanoparticles had spherical structures with diameters in the range of 198–201 nm. Further, MSPE was performed by dispersion of Fe₃O₄-SiO₂-C₁₈ paramagnetic nanoparticles in a buffered aqueous solution accompanied by sonication. Next, the sorbents were accumulated by applying an external magnetic field and were washed with 4-(2-pyridylazo) resorcinol-dimethyl sulfoxide solution, for the purpose of desorbing the analyte. The extraction conditions (sample pH, washing and elution solutions, amount of sorbents, time of extraction, sample volume and effect of diverse ions), as well as Zineb-PAR first-order derivative spectra, were also evaluated. The calibration curve of the method was linear in the concentration range of 0.055–24.3 mg L^?1 with a correlation coefficient of 0.991. The limit of detection and limit of quantification values were 0.022 and 0.055 mg L^?1, respectively. The precision of the method for 0.27 mg L^?1 solution of the analyte was found to be less than 3.2%. The recoveries of three different concentrations (0.27, 1.37 and 13.7 mg L^?1) obtained 98.3%, 98.5% and 96.0%, respectively. The proposed Fe₃O₄-SiO₂-C₁₈ paramagnetic nanoparticles were found to have the capability of reusing for 7.0 times.     

Highly sensitive simultaneous quantification of buprenorphine and norbuprenorphine in human plasma by magnetic solid-phase extraction based on P<Emphasis Type="Italic">p</Emphasis>PDA/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocomposite and high-performance liquid chromatography

A rapid and sensitive method based on magnetic solid-phase extraction coupled to high-performance liquid chromatography with ultraviolet detection was developed for the simultaneous determination of buprenorphine (BPN) and its major metabolite, norbuprenorphine (N-BPN), in human plasma samples. Poly (para-phenylenediamine)-modified Fe₃O₄ nanoparticles (PpPDA/Fe₃O₄) were synthesized and used as a magnetic adsorbent for the extraction and preconcentration of BPN and N-BPN in biological samples. The synthesized nanocomposites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and vibrating sample magnetometery. An isocratic separation was achieved on a Nova-Pak C18 reversed-phase column using a mobile phase consisting phosphate buffer (pH 3.4) and acetonitrile (50:50, v/v) at a flow rate of 1.0 mL min^?1. The detection was conducted at 280 nm. Under the optimum conditions, the calibration curves for BPN and N-BPN were linear in the ranges 3.0–150.0 and 1.0–120.0 ng mL^?1, respectively. The sensitivity was also high with limit of detection of 0.8 and 0.3 ng mL^?1 for BPN and N-BPN in plasma, respectively. The method was successfully applied to the extraction and determination of BPN and N-BPN in human plasma samples with an average recovery of 98.10 and 96.41%, respectively.     

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%.     

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).     

A chitosan–polypyrrole magnetic nanocomposite as μ-sorbent for isolation of naproxen

An extracting medium based on chitosan–polypyrrole (CS–PPy) magnetic nanocomposite was synthesized by chemical polymerization of pyrrole at the presence of chitosan magnetic nanoparticles (CS-MNPs) for micro-solid phase extraction. In this work, magnetic nanoparticles, the modified CS-MNPs and different types of CS–PPy magnetic nanocomposites were synthesized. Extraction efficiency of the CS–PPy magnetic nanocomposite was compared with the CS-MNPs and Fe₃O₄ nanoparticles for the determination of naproxen in aqueous samples, via quantification by spectrofluorimetry. The scanning electron microscopy images obtained from all the prepared nanocomposites revealed that the CS–PPy magnetic nanocomposite possess more porous structure. Among different synthesized magnetic nanocomposites, CS–PPy magnetic nanocomposite showed a prominent efficiency. Influencing parameters on the morphology of CS–PPy magnetic nanocomposite such as weight ratio of components was also assayed. In addition, effects of different parameters influencing the extraction efficiency of naproxen including desorption solvent, desorption time, amount of sorbent, ionic strength, sample pH and extraction time were investigated and optimized. Under the optimum condition, a linear calibration curve in the range of 0.04–10 μg mL⁻¹ (R² = 0.9996) was obtained. The limits of detection (3S_b) and limits of quantification (10S_b) of the method were 0.015 and 0.04 μg mL⁻¹ (n = 3), respectively. The relative standard deviation for water sample spiked with 0.1 μg mL⁻¹ of naproxen was 3% (n = 5) and the absolute recovery was 92%. The applicability of method was extended to the determination of naproxen in tap water, human urine and plasma samples. The relative recovery percentages for these samples were in the range of 56–99%.     

Synthesis and application of a novel magnetic nanosorbent for determination of trace Cd(II), Ni(II), Pb(II), and Zn(II) in environmental samples

In this work for the first time, Fe₃O₄@SiO₂ core–shell nanoparticles functionalized with isatin groups as a magnetic nanosorbent was applied for the simultaneous extraction of trace amounts of cadmium(II), nickel(II), lead(II), and zinc(II). The characterization of this nanosorbent was studied using Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffraction, vibrating sample magnetometer and thermogravimetric analysis. The effect of several factors such as pH, amount of sorbent, extraction time, type and volume of the eluent, sample volume, sorption capacity, and potentially interfering ions was investigated. In the selected conditions, it was observed that the limits of detection were 0.11 ng mL^?1 for Cd(II), 0.28 ng mL^?1 for Ni(II), 0.47 ng mL^?1 for Pb(II), and 0.21 ng mL^?1 for Zn(II), and the maximum sorption capacity of this suggested magnetic nanosorbent was 120, 112, 100, and 100 mg g^?1 for Cd(II), Ni(II), Pb(II), and Zn(II), respectively. Also, the precision of the method (RSD%) for ten replicate measurements was found 2.5, 2.5, 2.8, and 3.1%, for Cd(II), Ni(II), Pb(II), and Zn(II) ions, respectively. Finally, the suggested procedure was applied for determination of cadmium(II), nickel(II), lead(II), and zinc(II) at trace levels in different water and agricultural products with satisfactory results.     

Preconcentration of trace cadmium ion using magnetic graphene nanoparticles as an efficient adsorbent

Graphene-based magnetic nanoparticles (G-Fe₃O₄) were prepared and used as an effective adsorbent for the solid-phase extraction of trace quantities of cadmium from water and vegetable samples. The method avoids some of the time-consuming steps associated with traditional solid phase extraction. The excellent sorption property of the G-Fe₃O₄ system is attributed to π - π stacking interaction and hydrophobic interactions between graphene and the Cd-PAN complex. The effects of pH, the amount of G–Fe₃O₄, extraction time, type and volume of eluent, desorption time and interfering ions on the extraction efficiency were optimized. The preconcentration factor is 200. Cd(II) was then quantified by flame atomic absorption spectrometry with a detection limit of 0.32 ng mL^?1. The relative standard deviation (at 50 ng mL^?1; for n?=?10) is 2.45 %. The method has a linear analytical range from 1.1 to 150 ng mL^?1, and the recoveries in case of real samples are in the range between 93.1 % and 102.3 %.

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.     

A novel magnetic metal organic framework nanocomposite for extraction and preconcentration of heavy metal ions, and its optimization via experimental design methodology

We describe a novel magnetic metal-organic framework (MOF) prepared from dithizone-modified Fe₃O₄ nanoparticles and a copper-(benzene-1,3,5-tricarboxylate) MOF and its use in the preconcentration of Cd(II), Pb(II), Ni(II), and Zn(II) ions. The parameters affecting preconcentration were optimized by a Box-Behnken design through response surface methodology. Three variables (extraction time, amount of the magnetic sorbent, and pH value) were selected as the main factors affecting adsorption, while four variables (type, volume and concentration of the eluent; desorption time) were selected for desorption in the optimization study. Following preconcentration and elution, the ions were quantified by FAAS. The limits of detection are 0.12, 0.39, 0.98, and 1.2 ng mL^?1 for Cd(II), Zn(II), Ni(II), and Pb(II) ions, respectively. The relative standard deviations were <4.5 % for five separate batch determinations of 50 ng mL^?1 of Cd(II), Zn(II), Ni(II), and Pb(II) ions. The adsorption capacities (in mg g^?1) of this new MOF are 188 for Cd(II), 104 for Pb(II), 98 Ni(II), and 206 for Zn(II). The magnetic MOF nanocomposite has a higher capacity than the Fe₃O₄/dithizone conjugate. This magnetic MOF nanocomposite was successfully applied to the rapid extraction of trace quantities of heavy metal ions in fish, sediment, soil, and water samples.

Cetyltrimethylammonium-coated magnetic nanoparticles for the extraction of bromate,followed by its spectrophotometric determination

We report on a combination of magnetic solid-phase extraction and spectrophotometric determination of bromate. Cetyltrimethylammonium ion was adsorbed on the surface of phenyl-functionalized silica-coated Fe₃O₄ nanoparticles (Ph-SiO₂@Fe₃O₄), and these materials served as the sorbent. The effects of surfactant and amount of sorbent, the composition of the desorption solution, the extraction time and temperature were optimized. Under optimized conditions, an enrichment factor of 12 was achieved, and the relative standard deviation is 2.9 % (for n?=?5). The calibration plot covers the 1–50 ng mL^?1 range with reasonable linearity (r ²?>?0.998); and the limit of detection is 0.5 ng mL^?1. The method is not interfered by ionic compounds commonly found in environmental water samples. It was successfully applied to the determination of bromate in spiked water samples.