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.

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.

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.

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.

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.

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.

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.

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.

A surface ion-imprinted mesoporous sorbent for separation and determination of Pb(II) ion by flame atomic absorption spectrometry

A surface-imprinted mesoporous sorbent for Pb(II) ion was synthesized by the post-synthesis method. The material was characterized by transmission electron microscopy and nitrogen adsorption-desorption isotherms. The adsorption by the material was studied by batch experiments with respect to effects of pH value, contact time, kinetics, and adsorption isotherms. Both the pseudo-second-order kinetic model and the Langmuir model fit the experimental data well. Compared to other imprints for Pb(II), to the traditional sorbents and to the non-imprinted polymer, the new sorbent displays fast kinetics and higher selectivity. Pb(II) ion can be desorbed from the imprint with 2 M hydrochloric acid with high efficiency. The sorbent was applied to the selective separation and determination of Pb(II) in water and sediment samples with satisfactory results.

A colorimetric method for the determination of lead(II) ions using gold nanoparticles and a guanine-rich oligonucleotide

We have developed a colorimetric method for the determination of Pb(II) ions. It is based on the use of gold nanoparticles and a guanine-rich synthetic oligonucleotide. On addition of Pb(II), the color of the solution turns from red to blue. The ratio of the UV-vis absorption at 630?nm and 525?nm is proportional to the concentration of Pb(II) ions in the range from 10 to 100?nM, and the detection limit is 20?nM. Other metal ions do not interfere if present in up to a 10-fold molar excess. The method was successfully applied to the detection of Pb(II) in lake water and urine. The recovery in case of spiked samples is 92%. The results show that this method is sensitive, simple and fast.

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.

Multiwalled carbon nanotubes modified with 2-aminobenzothiazole modified for uniquely selective solid-phase extraction and determination of Pb(II) ion in water samples

A solid phase extraction method is presented for the selective preconcentration and/or separation of trace Pb(II) on multiwalled carbon nanotubes modified with 2-aminobenzothiazole. Inductively coupled plasma optical emission spectrometry was used for detection. The effects of pH, shaking time, sample flow rate and volume, elution condition and interfering ions were examined using batch and column procedures. An enrichment factor of 100 was accomplished. Common other ions do not interfere in both the separation and determination. The maximum adsorption capacity of the sorbent at optimum conditions is 60.3?mg?g^?1 of Pb(II), the detection limit (3??) is 0.27?ng?mL^?1, and the relative standard deviation is 1.6% (n?=?8). The method was validated using a certified reference material, and has been applied to the determination of trace Pb(II) in water samples with satisfactory results.

Solid-phase extraction of lead(II) ions using multiwalled carbon nanotubes grafted with tris(2-aminoethyl)amine

Multiwalled carbon nanotubes were grafted with tris(2-aminoethyl)amine (MWCNTs-TAA) and employed for solid phase extraction and preconcentration of trace lead ions prior to its determination by inductively coupled plasma optical emission spectrometry. The material was characterized by FT-IR and Raman spectroscopy, thermosgravimetric and elemental analysis. The effects of pH value, shaking time, sample volume, elution conditions and potentially interfering ions were investigated. Under the optimum conditions, the maximum adsorption capacity is 38?mg?g^?1 of Pb(II), the detection limit is 0.32?ng?mL^?1, the enrichment factor is 60, and the relative standard deviation is 3.5% (n?=?6). The method has been applied to the preconcentration of trace amounts of Pb(II) in environmental water samples with satisfactory results.

Colorimetric detection of lead (II) based on silver nanoparticles capped with iminodiacetic acid

We report on a colorimetric probe for the determination of Pb(II). It is based on the use of silver nanoparticles that have been functionalizd with iminodiacetic acid (IDA-Ag NPs). The absorption spectrum and solution color of IDA-Ag NPs undergo dramatic changes on exposure to Pb(II) with a new absorption peak appearing at 650 nm and a concomitant color change from yellow to green. This is assumed to result from the aggregation of IDA-Ag NPs induced by Pb(II). Under optimum conditions, there is a linear relationship between the ratio of the absorbances at 650 and 396 nm, respectively, and the concentration of Pb(II) in the 0.4 to 8.0 μM concentration range, with a detection limit of 13 nM. The method was applied to the determination of Pb(II) in tap water and urea samples, and recoveries ranged from 93.7 % to 98.6 %.

Square wave anodic stripping voltammetric determination of lead(II) using a glassy carbon electrode modified with a lead ionophore and multiwalled carbon nanotubes

We report on a glassy carbon electrode (GCE) modified with a lead ionophore and multiwalled carbon nanotubes. It can be applied to square wave anodic stripping voltammetric determination of Pb(II) ion after preconcentration of Pb(II) at ?1.0?V (vs. SCE) for 300?s in pH?4.5 acetate buffer containing 400?μg?L^?1 of Bi(III). The ionophore-MWCNTs film on the GCE possesses strong and highly selective affinity for Pb(II) as confirmed by quartz crystal microbalance experiments. Under the optimum conditions, a linear response was observed for Pb(II) ion in the range from 0.3 to 50?μg?L^?1. The limit of detection (at S/N?=?3) is 0.1?μg?L^?1. The method was applied to the determination of Pb(II) in water samples with acceptable recovery.

Determination of phenolic compounds in water samples by HPLC following ionic liquid dispersive liquid-liquid microextraction and cold-induced aggregation

We report on the determination of bisphenol A and 2-naphthol in water samples using ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction combined with HPLC. Parameters governing the extraction efficiency (disperser solvent, volume of extraction and disperser solvent, pH, temperature, extraction time) were optimized and resulted in enrichment factors of 112 for bisphenol A and of 186 for 2-naphthol. The calibration curve was linear with correlation coefficients of 0.9995 and 0.9998, respectively, in the concentration range from 1.5 to 200?ng?mL^?1. The relative standard deviations are 2.3% and 4.1% (for n?=?5), the limits of detection are 0.58 and 0.86?ng?mL^?1, and relative recoveries in tap, lake and river water samples range between 100.1 and 108.1%, 99.4 and 106.2%, and 97.1 and 103.8%, respectively.

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.

Voltammetric determination of cadmium (II) based on a composite film of a thiol-functionalized mesoporous molecular sieve and an ionic liquid

A composite film made from a thiol-functionalized mesoporous molecular sieve and an ionic liquid is introduced for use in a voltammetric sensor for Cd(II). The electrode exhibits excellent sensitivity towards Cd(II) in showing a markedly increased stripping peak current. Following the optimization of the experimental parameters, a linear response is obtained in the concentration range from 29?nM to 0.87?mM of Cd(II). The detection limit is as low as 1.0?nM (at S/N?=?3) after an accumulation at ?1.1?V for 4?min. The method was successfully applied to determine Cd(II) in water samples. Features such as large electroactive area, fast electron transfer and low background current make this electrode a promising platform for fabricating reliable electrochemical sensors for various species, such as heavy metals and environmental pollutants.