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.

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 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.

Solid phase extraction of Cd(II), Pb(II), Zn(II) and Ni(II) from food samples using multiwalled carbon nanotubes impregnated with 4-(2-thiazolylazo)resorcinol

Multiwalled carbon nanotubes were impregnated with 4-(2-thiazolylazo)resorcinol and used for the separation and preconcentration of Cd(II), Pb(II), Zn(II) and Ni(II) ions from food samples. The analytes were quantitatively recovered at pH 7.0 and eluted with 3?mol?L^?1 acetic acid. The effects of pH value, flow rate, eluent type and sample volume on the recoveries, and the effects of alkali, earth alkali and transition metals on the retention of the analytes were studied. The method was validated using the standard certified reference materials SRM 1570A (spinach leaves) and IAEA 336 (lichen), and the results were found to be compatible with the certified values of reference materials. The new enrichment procedure was applied to the determination of these ions in various food 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.

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.

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.

Determination of cadmium(II) using carbon paste electrode modified with a Cd-ion imprinted polymer

We have synthesized cadmium(II) ion-imprinted polymers (IIP) and non-imprinted polymers (NIP) using 1-(2-pyridylazo)-2-naphthol as a ligand. The materials were used to prepare a carbon paste electrode for the determination of Cd(II). Polymerization was performed with (a) methacrylic acid as a functional monomer, (b) ethyleneglycol dimethacrylate as the crosslinking monomer, and (c) 2,2′-azobis(isobutyronitrile) as the initiator. Imprinted cadmium ion was removed from the polymeric matrix using nitric acid. The measurements were carried out in an closed circuit after accumulation at ?1.2?V, this followed by electrolysis of the accumulated Cd(II) by voltammetric scanning from ?1.0 to ?0.6?V. The parameters governing the response of the electrode were studied. Under optimized conditions, the response of the electrode is linear in the range from 2.0 to 200?ng?mL^?1. The detection limit is 0.31?ng?mL^?1. The relative standard deviations are ±3.4 and ±2.1?% for 7 successive determinations of 20.0 and 50.0?ng?mL-1 of Cd(II), respectively. The method was applied to the determination of cadmium (II) in water and food samples.

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.

Chemically modified alumina nanoparticles for selective solid phase extraction and preconcentration of trace amounts of Cd(II)

We have developed a solid phase extraction method for the determination of cadmium ions in aqueous samples. It is based on the adsorption of Cd(II) on alumina nanoparticles coated with sodium dodecyl sulfate and modified with a newly synthesized Schiff base. Analytical parameters such as pH value, amount of adsorbent, type and concentration of eluent, flow rates of the sample and eluent, sample volume and matrix effects were optimized. Desorption is accomplished with 2?mol?L^?1 nitric acid. Cd(II) was then determined by flame atomic absorption spectrometry. The maximum enrichment factor is 75. Under the optimum experimental conditions, the detection limit is 0.14???g?L^?1 in original solution. The adsorption capacity of the modified sorbent is 4.90?mg?g^?1 for cadmium ions. The method was applied to the determination of trace quantities of Cd(II) in water, wastewater, and biological and food samples with satisfactory results.

A nanosized cadmium(II)-imprinted polymer for use in selective trace determination of cadmium in complex matrices

We describe a nanosized Cd(II)-imprinted polymer that was prepared from 4-vinyl pyridine (the functional monomer), ethyleneglycol dimethacrylate (the cross-linker), 2,2′-azobisisobutyronitrile (the radical initiator), neocuproine (the ligand), and Cd(II) (the template ion) by precipitation polymerization in acetonitrile as the solvent. The imprinted polymer was characterized by X-ray diffraction, thermogravimetric analysis, differential thermal analysis, and scanning electron microscopy. The maximum adsorption capacity of the nanosized sorbent was calculated to be 64 mg g^?1. Cadmium(II) was then quantified by FAAS. The relative standard deviation and limit of detection are 4.2 % and 0.2 μg L^?1, respectively. The imprinted polymer displays improve selectivity for Cd(II) ions over a range of competing metal ions with the same charge and similar ionic radius. This nanosized sorbent is an efficient solid phase for selective extraction and preconcentration of Cd(II) in complex matrices. The method was successfully applied to the trace determination of Cd(II) in food and water samples.

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

Lead ion sensor with electrodes modified by imidazole-functionalized polyaniline

Glassy carbon electrodes (GCE) and carbon paste electrodes (CPE) were modified with imidazole functionalized polyaniline with the aim to develop a sensor for lead (II) in both acidic and basic aqueous solution. The electrodes were characterized by cyclic voltammetry and differential pulse adsorptive stripping voltammetry. The limit of detections obtained with glassy carbon electrode and carbon paste electrode are 20?ng?mL^-1 and 2?ng?mL^-1 of lead ion, respectively. An interference study was carried out with Cd(II), As(III), Hg(II) and Co(II) ions. Cd(II) ions interfere significantly (peak overlap) and As(III) has a depressing effect on the lead signal. The influence of pH was investigated indicating that bare and modified GCE and CPE show optimum response at pH?4.0 ± 0.05.

Solid phase ligand-less extraction of cadmium(II) using a silica gel modified with an amino-functionalized ionic liquid

A method was developed for the determination of cadmium(II) by ligand-less solid phase extraction that is based on the direct retention of Cd(II) in a mini-column filled with a silica gel modified with an amino-functionalized ionic liquid. The effects of pH, sample volume and its flow rate, eluent concentration and its volume, the flow rate of eluent, and of potential interferences on extraction and desorption were optimized. Following its determination by electrothermal atomic absorption spectrometry, the detection limit for Cd(II) is 8.9 ng L^?1, and the relative standard deviation is 2.3 % (at 1.0 ng mL^?1; for n?=?5). The method was applied to the analysis of Cd(II) in a certified reference material (laver; GBW10023), and the recoveries ranged from 97.0 to104.0 %

Dispersive liquid-liquid microextraction for simultaneous determination of cadmium, cobalt, lead and nickel in water samples by inductively coupled plasma optical emission spectrometry

We report on a new method for the dispersive liquid-liquid microextraction of Cd(II), Co(II), Pb(II) and Ni (II) from water samples prior to their simultaneous determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The procedure is based on the injection of a ternary solvent system composed of appropriate quantities of extraction solvent (trichloroethylene), dispersive solvent (ethanol), and the chelating reagent 2-(2′-benzothiazolylazo)-p-cresol into the sample solution. The solution turns turbid immediately after injection, and the analytes are extracted into the droplets of the organic phase which was dried and dissolved in a mixture of Triton X-114, nitric acid, and ethanol. The metal ions in this mixture were quantified by ICP-OES. The detection limits under optimized conditions are 0.2, 0.3, 0.2 and 0.7?μg?L^?1 for Cd(II), Co(II), Pb(II) and Ni(II), respectively. The enrichment factors were also calculated for Cd (13), Co (11), Pb (11) and Ni (8). The procedure was applied to the determination of cadmium, cobalt, lead and nickel in certified reference material (waterway sediment) and water samples.

Ionic liquid based dispersive liquid-liquid microextraction combined with ICP-OES for the determination of trace quantities of cobalt, copper, manganese, nickel and zinc in environmental water samples

We describe a method for ionic liquid based dispersive liquid-liquid microextraction of Co(II), Cu(II), Mn(II), Ni(II) and Zn(II), followed by their determination via flow injection inductively coupled plasma optical emission spectrometry. The method is making use of the complexing agent 1-(2-thenoyl)-3,3,3-trifluoracetone, the ionic liquid 1-hexyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide, and of ethanol as the dispersing solvent. After extraction and preconcentration, the sedimented ionic liquid (containing the target analytes) is collected, diluted with 1-propanol, and introduced to the ICP-OES. Effects of pH, ionic strength, ligand to metal molar ratio, volumes of extraction and disperser solvents on the performance of the microextraction were optimized in a half-fractional factorial design. The significant parameters were optimized using a face-centered central composite design. The method has detection limits between 0.10 and 0.20?ng?mL^?1 of the metal ions, preconcentration factors between 79 and 102, linear responses in 0.25 to 200?ng?mL^?1 concentration ranges, and relative standard deviations of 3.4 to 6.0%. The method was successfully applied to the analysis of drinking water, a fish farming pond water, and waste water from an industrial complex.

Novel phenyl-iminodiacetic acid grafted multiwalled carbon nanotubes for solid phase extraction of iron, copper and lead ions from aqueous medium

We have covalently grafted phenyl-iminodiacetic acid groups onto multi-walled carbon nanotubes via a diazotation reaction. The resulting material was characterized by FT-IR and UV–vis spectroscopy, by TGA, XPS and SEM. It is shown to be a valuable solid-phase extraction adsorbent for the preconcentration of trace quantities of Fe(III), Cu(II) and Pb(II) ion from aqueous solution prior to their determination by ICP-OES. Various factors affectting the separation and preconcentration were investigated. The enrichment factor typically is 100. Under optimized experimental conditions, the maximum adsorption capacities for Fe(III), Cu(II) and Pb (II) are 64.5, 30.5 and 17.0?mg?g-1, respectively, the detection limits are 0.26, 0.15 and 0.18?ng?mL-1, and the relative standard deviations are <2.5% (n?=?6). The new adsorbent shows superior reusability and stability. The procedure was successfully applied to the determination of trace quantities of Fe(III), Cu(II) and Pb (II) in water samples.

Preconcentration and separation of ultra-trace palladium ion using pyridine-functionalized magnetic nanoparticles

We present a study on the application of magnetic nanoparticles (MNPs) prepared from Fe₃O₄ and functionalized with pyridine as an adsorbent for the solid-phase extraction of trace quantities of Pd(II) ion. The pyridine group was immobilized on the surface of the MNPs by covalent bonding of isonicotinamide. The modified MNPs can be readily separated from an aqueous solution by applying an external magnetic field. Effects of pH, the amount of functionalized MNPs, extraction time, type and quantity of eluent, desorption time, break-through volume and interfering ions on the extraction efficiency were optimized. The amount of Pd(II) was then determined using FAAS. Under the optimized conditions, the detection limit and preconcentration factor are 0.15?μg?L^-1 and 196, respectively, and the relative standard deviation (at 20?μgL^?1; for n?=?10) is 3.7?%. The method had a linear analytical range from 1 to 80?μg?L^-1 and was applied to determine Pd(II) in spiked tape water and soil.

Colorimetric and bare-eye detection of alkaline earth metal ions based on the aggregation of silver nanoparticles functionalized with thioglycolic acid

We describe a simple and rapid method for colorimetric and bare-eye detection of the alkaline earth metal ions Mg(II), Ca(II), Sr(II) and Ba(II) based on the use of silver nanoparticles (AgNPs) functionalized with thioglycolic acid (TGA). The TGA ligand was self-assembled onto the AgNPs to form a probe that undergoes a color change from yellow to orange or red on exposure to the alkaline earth ions. It is presumed that the color change is a result of the aggregation of the AgNPs caused by the interaction of the bivalent ions with the carboxy groups on the AgNPs. The color change can be used for bare-eye and colorimetric determination of the alkaline earth metal ions, for example to rapidly determine water hardness.

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