Solid phase extraction of heavy metal ions based on a novel functionalized magnetic multi-walled carbon nanotube composite with the aid of experimental design methodology

We report that magnetic multiwalled carbon nanotubes functionalized with 8-aminoquinoline can be applied to the preconcentration of Cd(II), Pb(II) and Ni(II) ions. The parameters affecting preconcentration were optimized by a Box-Behnken design through response surface methodology. Three variables (extraction time, magnetic sorbent amount, and pH value) were selected as the main factors affecting sorption, and four variables (type, volume and concentration of the eluent; elution time) were selected for optimizing elution. Following sorption and elution, the ions were quantified by FAAS. The LODs are 0.09, 0.72, and 1.0 ng mL^?1 for Cd(II), Ni(II), and Pb(II) ions, respectively. The relative standard deviations are <5.1 % for five separate batch determinations at 30 ng mL^?1 level of Cd(II), Ni(II), and Pb(II) ions. The sorption capacities (in mg g^?1) of this new sorbent are 201 for Cd(II), 150 for Pb(II), and 172 Ni(II). The composite was successfully applied to the rapid extraction of trace quantities of heavy metal ions in fish, sediment, soil, and water samples.

A nanostructured ion-imprinted polymer for the selective extraction and preconcentration of ultra-trace quantities of nickel ions

We describe a nanostructured ion-imprinted polymer (IIP) for the selective preconcentration of Ni(II) ions. It was obtained by bulk polymerization from 2-vinylpyridine (the functional monomer), ethylene glycol dimethacrylate (the cross-linker), 2,2′-azobisisobutyronitrile (the initiator), alizarin red S (the nickel-binding ligand), and nickel (the template ion) in acetonitrile solution. The IIP particles were characterized by elemental analysis, X-ray diffraction, Fourier transform IR spectroscopy, thermogravimetric and differential thermal analysis, and by scanning electron microscopy. Imprinted Ni(II) ions were removed from the polymeric structure using 5 % HCl as the eluting solvent. The material is capable of selectively binding Ni(II) from solutions at pH values between (pH 8.0 being best). Both the sorption and desorption process occur within 5 min. The maximum sorbent capacity of the ion imprinted polymer is 73 mg g^?1. Following desorption, Ni(II) was determined by FAAS, with relative standard deviation and limit of detection of 3.4 % and 0.15 ng mL^?1, respectively. The method was applied to the determination of nickel in certified reference materials (soil and polymetallic gold ore), fish, vegetables, river sediments, and river water.

Supported hydrophobic ionic liquid on magnetic nanoparticles as a new sorbent for separation and preconcentration of lead and cadmium in milk and water samples

We have prepared a highly selective and efficient sorbent for the simultaneous separation and preconcentration of lead and cadmium ions from milk and water samples. An ionic liquid was deposited on the surface of magnetic nanoparticles (IL-MNPs) and used for solid phase extraction of these ions. The IL-MNPs carrying the target metals were then separated from the sample solution by applying an external magnetic field. Lead and cadmium were almost quantitatively retained by the IL-MNPs, and then eluted with nitric acid. The effect of different variables on solid phase extraction was investigated. The calibration curve is linear in the range from 0.3 to 20?ng mL^?1 of Cd(II), and from 5 to 330?ng mL^?1 of Pb(II) in the initial solution. Under optimum conditions, the detection limits are 1.61 and 0.122?μg?L-1 for Pb(II) and Cd(II) respectively. Relative standard deviations (n?=?10) were 2.87?% and 1.45?% for 0.05?μg?mL^-1 and 0.2?μg?mL^-1 of Cd (II) and Pb (II) respectively. The preconcentration factor is 200 for both of ions.

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.

Comparison of the performance of different modified graphene oxide nanosheets for the extraction of Pb(II) and Cd(II) from natural samples

Graphene nanosheets were modified with amino groups and the resulting material was used as a sorbent for the extraction of cadmium and lead ions. The nanosheets were characterized by IR spectroscopy, transmission electron microscopy, thermal gravimetric analysis and elemental analysis. The effects of sample pH, eluent parameters (type, concentration and volume of eluent), flow rates (of both sample and eluent), and of a variety of other ions on the efficiency of the extraction of Cd(II) and Pb(II) were optimized. Following solid phase extraction, the elements were determined by FAAS. The limits of detection are <0.9 μg L^?1 for Pb(II) and <5 ng L^?1 for Cd(II). The relative standard deviations are <2.2 %. The method was validated by analyzing several certified reference materials and was then used for Pb(II) and Cd(II) determination in natural waters and vegetables.

Triazine-modified magnetite nanoparticles as a novel sorbent for preconcentration of lead and cadmium ions

We report on a new sorbent for preconcentration of cadmium and lead ions that is based on triazine-functionalized magnetite nanoparticles that were prepared by direct silylation of magnetic nanoparticles with 3-aminopropyltriethoxysilane-2,4-bis(3,5-dimethylpyrazol)-triazine. The sorbent was characterized by IR spectroscopy, X-ray powder diffraction, scanning electron microscopy, thermal and elemental analysis. The sorbent was applied to the preconcentration of lead and cadmium ions which then were quantified by FAAS. The effects of sample pH value, extraction time, of type, concentration and volume of eluent, and of elution time were optimized. The limits of detection are 0.7 ng mL^?1 for Pb(II) ion and 0.01 ng mL^?1 for Cd(II). The effects of potentially interfering ions often found in real samples on the recovery in the determination of cadmium and lead ions in real samples were also investigated. The accuracy of the method was confirmed by analyzing the certified reference materials NIST 1571 (orchard leaves) and NIST 1572 (citrus leaves). Finally, the method was successfully applied to the determination of cadmium and lead ions in some fruit samples. Figure

We report on a new sorbent for preconcentration of cadmium and lead ions that is based on triazine-functionalized magnetite nanoparticles. After optimization of the preconcentration step the method was successfully applied to the determination of cadmium and lead ions in some fruit samples     

Removal of heavy metals from industrial wastewaters using amine-functionalized nanoporous carbon as a novel sorbent

Nano-porous carbon (NPC) was synthesized by hydrothermal condensation of fructose and characterized by X-ray powder diffraction and also nitrogen adsorption analysis. It was then modified with amino groups and used as a sorbent for the removal of heavy metal ions. The formation of amino-modified NPC was confirmed by X-ray powder diffraction, infrared spectroscopy, thermogravimetric and elemental analysis. NPC was applied for removal of Pb(II), Cd(II), Ni(II) and Cu(II) ions. The effects of sample pH and the adsorption kinetics were studied, and the adsorption capacity was determined. The sorbent was applied to the removal of heavy metal ions in industrial waste water samples.

Dithizone-modified nanoporous fructose as a novel sorbent for solid-phase extraction of ultra-trace levels of heavy metals

We are introducing nanoporous fructose (np-F) modified with dithizone as a new solid-phase for extraction of heavy metals ions including cadmium(II), copper(II), nickel(II) and lead(II). Effects of pH value, flow rates, type, concentration and volume of the eluent, breakthrough volume, and of other ions were studied. Under optimized conditions, the extraction efficiency is >97 %, and the limits of detection are 0.025, 0.15, 0.5 and 1.2 ng mL^?1 for the ions of cadmium, copper, nickel, and lead, respectively, and the adsorption capacities for these ions are 101, 81, 74 and 178 mg g^?1. The modified np-F sorbent was characterized by thermogravimetric analysis, differential thermal analysis, transmission electron microscopy, Fourier transform infrared spectrometry, X-ray diffraction, and nitrogen adsorption surface area (BET) measurements.

Solid phase extraction of Cd(II) and Pb(II) using a magnetic metal-organic framework, and their determination by FAAS

We describe a novel magnetic metal-organic framework (MOF) for the preconcentration of Cd(II) and Pb(II) ions. The MOF was prepared from the Fe₃O₄-pyridine conjugate and the copper(II) complex of trimesic acid. The MOF was characterized by IR spectroscopy, elemental analysis, SEM and XRD. A Box-Behnken design through response surface methodology and experimental design was used to identify the optimal parameters for preconcentration. Extraction time, amount of magnetic MOF and pH value were found to be critical factors for uptake, while type, volume, concentration of eluent, and elution time are critical in the elution step. The ions were then determined by FAAS. The limits of detection are 0.2 and 1.1 μg?L^?1 for Cd(II), and Pb(II) ions, respectively, relative standard deviations are <4.5% (for five replicates at 50 μg?L^?1 of Cd(II) and Pb(II) ions), and the enrichment capacity of the MOF is at around 190 mg?g^?1 for both ions which is higher than the conventional Fe3O4-pyridine material. The magnetic MOF was successfully applied to the rapid extraction of trace quantities of Cd(II) and Pb(II) ions in fish, sediment, and water samples.

Novel ion-imprinted polymer coated on nanoporous silica as a highly selective sorbent for the extraction of ultratrace quantities of gold ions from mine stone samples

We have developed a gold ion-imprinted polymer (GIP) by incorporating a dipyridyl ligand into an ethylene glycol dimethacrylate matrix which then was coated onto porous silica particles. The material was used for the selective extraction of ultratrace quantities of gold ion from mine stones, this followed by its quantitation by FAAS. The effects of concentration and volume of eluent, pH of the solution, flow rates of sample and eluent, and effect of potentially interfering ions, especially palladium and platinum, was investigated. The limit of detection is <0.2 ng?mL^?1, the precision (RSD%) is 1.03 %, and recoveries are >99 %. In order to show the high selectivity and efficiency of the new sorbent, the results were compared to those obtained with more simple sorbents possessing the same functional groups. The accuracy of the method was demonstrated by the accurate determination of gold ions in a certified reference material. To the best of our knowledge, there is no report so far on an imprint for gold ions that has such a selectivity over Pd(II) and Pt(II) ions.

Functionalization of cross linked chitosan with 2-aminopyridine-3-carboxylic acid for solid phase extraction of cadmium and zinc ions and their determination by atomic absorption spectrometry

We have developed a new method for solid phase extraction (SPE) and preconcentration of trace amounts of cadmium and zinc using cross linked chitosan that was functionalized with 2-aminopyridine-3-carboxy acid. Analytical parameters, sample pH, effect of flow rate, sample volume, and concentration of eluent on column SPE were investigated. The effect of matrix ions on the recovery of cadmium and zinc has been investigated and were found not to interfere with preconcentration. Under the optimum experimental conditions, the preconcentration factors for Cd(II) and Zn(II) were found to be 90. The two elements were quantified via atomic absorption spectrometry. The detection limits for cadmium and zinc are 21 and 65?ng?L^?1, respectively. The method was evaluated by analyzing a certified reference material (NIST 1643e; water) and has been successfully applied to the analysis of cadmium and zinc in environmental water samples.

Emulsification based dispersive liquid microextraction prior to flame atomic absorption spectrometry for the sensitive determination of Cd(II) in water samples

We report on the application of emulsification-based dispersive liquid microextraction (EB-DLME) to the preconcentration of Cd(II). This procedure not only possesses all the advantages of routine DLLME, but also results in a more stable cloudy state which is particularly useful when coupling it to FAAS. In EB-DLME, appropriate amounts of the extraction solvent (a solution of dithizone in chloroform) and an aqueous solution of sodium dodecyl sulfate (SDS; acting as a disperser) are injected into the samples. A stable cloudy microemulsion is formed and Cd(II) ion is extracted by chelation. After phase separation, the sedimented phase is subjected to FAAS. Under optimized conditions, the calibration curve for Cd(II) is linear in the range from 0.1 to 25 μg L^?1, the limit of detection (at S/N?=?3) is 30 pg L^?1, the relative standard deviations for seven replicate analyses (at 0.56 μg L^?1 of Cd(II)) is 4.6 %, and the enrichment factor is 151. EB-DLME in our opinion is a simple, efficient and rapid method for the preconcentration of Cd(II) (and most likely of many other ions) prior to FAAS determination.

Preconcentration of trace lead via formation of the bis(2,2-bipyridyl) complex and its adsorption on oxidized multiwalled carbon nanotubes

A solid phase extraction method is presented for the preconcentration of trace lead ions on oxidized multiwalled carbon nanotubes (ox-MWCNTs). In the first step, the cationic Pb(II) complex of 2,2-bipyridyl is formed which, in a second step, is adsorbed on ox-MWCNTs mainly due to electrostatic and van der Waals interactions. The Pb(II) ions were then eluted with dilute nitric acid and quantified by FAAS. The effects of pH value, mass of sorbent, concentration of 2,2-bipyridyl, stirring time, of type, concentration and volume of eluent, of eluent flow rate and sample volume were examined. Most other ions do not affect the recovery of Pb(II). The limits of detection are 240 and 60 ng L^?1 for sample volumes of 100 and 400 mL, respectively. The recovery and relative standard deviation are >95 % and 2.4 %, respectively. Other figures of merit include a preconcentration factor of 160 and a maximum adsorption capacity of 165 mg g^?1. The method was successfully applied to the determination of Pb(II) in spiked tap water samples. The accuracy of the method was verified by correctly analyzing a certified reference material (NCS ZC85006; lead in tomatoes).

Magnetic ion imprinted polymer nanoparticles for the preconcentration of vanadium(IV) ions

An ion imprinted polymer coated onto magnetite (Fe₃O₄) nanoparticles is shown to be a useful magnetic sorbent for the fairly selective preconcentration of vanadium. The sorbent was prepared by radical copolymerization of 3-(triethoxysilyl)propyl methacrylate (the monomer), ethylene glycol dimethacrylate (the cross-linker), and the vanadium(IV) complex of 1-(2-pyridylazo-2-naphthol) in the presence of magnetite nanoparticles. The material was characterized by IR spectroscopy, scanning electron microscopy, and thermal analysis. The vanadium(IV) ions were removed from the imprint by a solution containing thiourea and HCl, and the eluent was submitted to AAS. The analytical efficiency and relative standard deviation are 99.4 and ±2.3 %, respectively, under optimum conditions, and the limit of detection is 20 ng mL^?1. The method was successfully applied to the preconcentration and determination of vanadium(IV) ions in crude oil. Figure

An ion imprinted polymer is coated on to magnetite nanoparticles as a useful magnetic sorbent for the fairly selective preconcentration of vanadium which can be used for vanadium determination in crude oil.     

Flame atomic absorption spectrometric determination of trace amounts of Pb(II) and Cr(III) in biological, food and environmental samples after preconcentration by modified nano-alumina

A new solid-phase extraction sorbent was used for the preconcentration of Pb(II) and Cr(III) ions prior to their determination by flame atomic absorption spectrometry. It was prepared by immobilization of 2,4-dinitrophenylhydrazine on nano-alumina coated with sodium dodecyl sulfate. The sorbent was characterized by scanning electron microscopy, N₂ adsorption and Fourier transform infrared spectrometry, and used for preconcentration and separation of Pb(II) and Cr(III) from aqueous solutions. The ions on the sorbent were eluted with a mixture of nitric acid and methanol. The effects of sample pH, flow rates of samples and eluent, type of eluent, breakthrough volume and potentially interfering ions were studied. Linearity is maintained between 1.2 and 350???g?L^-1 of Pb(II), and between 2.4 and 520???g?L^-1 of Cr(III) for an 800-mL sample. The detection limit (3?s, N?=?10) for Pb(II) and Cr(III) ions is 0.43 and 0.55???g?L^-1, respectively, and the maximum preconcentration factor is 267. The method was successfully applied to the evaluation of these trace and toxic metals in various water, food, industrial effluent and urine samples.

A new ion imprinted polymer based on Ru(III)-thiobarbituric acid complex for solid phase extraction of ruthenium(III) prior to its determination by ETAAS

A new ruthenium ion imprinted polymer was prepared from the Ru(III) 2-thiobarbituric acid complex (the template), methacrylic acid or acrylamide (the functional monomers), and ethylene glycol dimethacrylate (the cross-linking agent) using 2,2′-azobisisobutyronitrile as the radical initiator. The ion imprinted polymer was characterized and used as a selective sorbent for the solid phase extraction of Ru(III) ions. The effects of type of functional monomer, sample volume, solution pH and flow rate on the extraction efficiency were studied in the dynamic mode. Ru(III) ion was quantitatively retained on the sorbents in the pH range from 3.5 to 10, and can be eluted with 4 mol L^?1 aqueous ammonia. The affinity of Ru(III) for the ion imprinted polymer based on the acrylamide monomer is weaker than that for the polymer based on the methacrylic acid monomer, which therefore was used in interference studies and in analytical applications. Following extraction of Ru(III) ions with the imprint and their subsequent elution from the polymer with aqueous ammonia, Ru(III) was detected by electrothermal atomic absorption spectrometry with a detection limit of 0.21 ng mL^?1. The method was successfully applied to the determination of trace amounts of Ru(III) in water, waste, road dust and platinum ore (CRM SARM 76) with a reproducibility (expressed as RSD) below 6.4 %.

Electromagnetic induction-assisted heating as a new method for on-line cloud point extraction of cadmium from water samples

We report on a novel method for on-line cloud point extraction (CPE) for preconcentration of cadmium ions. It is based on electromagnetic induction-assisted heating (EMIH) of iron particles in a packed bed contained in a quartz tube that acts as an on-line CPE enrichment column. The cadmium complex of 1-(2-pyridylazo)-2-naphthol is quantitatively retained by the column under the cloud point temperature with the help of EMIH. The column was then eluted with alcoholic borax buffer at room temperature and on-line coupled to FAAS. Under optimum conditions, the limit of detection (3 s_b/b) and limit of quantification (10 s_b/b) are 0.21 μg?L^?1 and 0.70 μg?L^?1 of Cd(II), respectively, and the relative standard deviation is 3.8 % (for n?=?8; at 20 ng?mL^?1). An enhancement factor of 76 is typically achieved. The correlation coefficient of the calibration graph using the present method was 0.9986. The method was successfully applied to determine Cd(II) in water samples

Flame photometric determination of cesium ion after its preconcentration with nanoparticles imprinted with the cesium-dibenzo-24-crown-8 complex

We report on the synthesis of cesium ion-imprinted polymer nanoparticles that were prepared by a precipitation polymerization strategy using dibenzo-24-crown-8 ether as a selective crown ether, methacrylic acid as the functional monomer, ethyleneglycol dimethacrylate as the crosslinker, and AIBN as the radical initiator. The prepared sorbents have a diameter of 50–90 nm and display highly selective binding capability for Cs(I) ion, with rapid adsorption and desorption. The maximum adsorption capacity is 50 mg g^?1, and the preconcentration factor is around 100 at pH 9.0. Cesium ion was then determined by flame photometry with a detection limit (3σ) of 0.7 ng mL^?1 and with a standard deviation of 0.9 %.

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 %.

A magnetic metal-organic framework as a new sorbent for solid-phase extraction of copper(II), and its determination by electrothermal AAS

We report on the synthesis of Fe₃O₄-functionalized metal-organic framework (m-MOF) composite from Zn(II) and 2-aminoterephthalic acid by a hydrothermal reaction. The magnetic composite is iso-reticular and was characterized by FTIR, X-ray diffraction, SEM, magnetization, and TGA. The m-MOF was then applied as a sorbent for the solid-phase extraction of trace levels of copper ions with subsequent quantification by electrothermal AAS. The amount of sorbent applied, the pH of the sample solution, extraction time, eluent concentration and volume, and desorption time were optimized. Under the optimum conditions, the enrichment factor is 50, and the sorption capacity of the material is 2.4 mg g^?1. The calibration plot is linear over the 0.1 to 10 μg L^?1 Cu(II) concentration range, the relative standard deviation is 0.4 % at a level of 0.1 μg L^?1 (for n?=?10), and the detection limit is as low as 73 ng L^?1. We consider this magnetic MOF composite to be a promising and highly efficient material for the preconcentration of metal ions.