Preconcentration Of Zn Research Articles

Electrochemical determination of zinc(II) using N1-hydroxy-N1,N2-diphenylbenzamidine and multi-walled carbon nanotubes modified carbon paste electrode

In this study, a new carbon paste electrode modified with a laboratory-synthesized ligand, N1-hydroxy-N1,N2-diphenylbenzamidine (HDPBA) and multi-walled carbon nanotubes (MWCNTs) (HDPBA‒MWCNTs/CPE) has been developed. The modified electrode was applied for preconcentration and voltammetric determination of zinc ions (Zn(II)) by square wave anodic stripping voltammetry (SWASV). The preconcentration of Zn(II) on the electrode surface was performed in 0.1M Brinton Robinson (B-R) buffer solution (pH 6) at an applied potential of -1.30V versus Ag/AgCl for 120s, followed by stripping in the positive potential scan of the SWASV after a quit time of 10s. Under optimized experimental conditions, the proposed electrode exhibited a wider linear dynamic response for Zn(II) in a concentration range of 0.02-10.00μM with a detection limit of 2.48nM. This is due to the excellent metal-chelation property of the ligand, and the good conductivity and large surface area of MWCNTs which significantly improved the sensing performance of the nanocomposite modified electrode. The selectivity of the electrode was studied by evaluating the interference effects of various foreign ions on the peak current of Zn(II). The method exhibited high reproducibility with a relative standard deviation (RSD) of 3.1%. The present method was applied for the determination of zinc ions in water samples. The recovery values in the tested samples were found to be 98.50-106.0%, indicating a good accuracy of the proposed electrode. Furthermore, the electrochemical behavior of HDPBA in acetonitrile and aqueous solutions has been studied.

Synthesis, characterization and analytical applications of cobalt ferrite nanoparticles

• CoFe 2 O 4 nanoparticless have been prepared. • The isolated nanoparticles have been characterized by IR, XRD, TEM and SAED • The analytical applications of CoFe 2 O 4 have been studied. A simple, rapid, and reliable method for adsorptive separation and pre-concentration of Zn(II) ions in aqueous solution using cobalt ferrite nanoparticles as adsorbent followed by spectrophotometric determination has been developed. Cobalt ferrite nanoparticles (CFNs) have been synthesized by co-precipitation method and characterized by infrared (IR), x-ray powder diffraction (XRD), high resolution transmittance electron microscope (HR-TEM) and selected area electron diffraction (SAED). The results indicated that the average particle size is 8.0 nm. The results of the adsorptive separation and pre-concentration of Zn(II) ions using CoFe 2 O 4 nanoparticles as adsorbent showed an extraction recovery > 98% from 50 mL aqueous sample at pH 8, initial Zn(II) concentration 0.05 mg/L, adsorbent dose 2 g/L and 2 mL of 0.5 M HNO 3 as eluent. The pre-concentration factor obtained was 25 under these optimum conditions. The pre-concentration factor obtained was 25 under ideal experimental circumstances. The suggested method was successfully applied for determination of trace zinc concentrations in several water samples using flame atomic absorption spectrophotometry and satisfactory results were obtained.

Enhanced Adsorption of Zn(II) onto Graphene Oxides Investigated Using Batch and Modeling Techniques.

Graphene oxide (GO) was synthesized and employed as an adsorbent for Zn(II) removal from an aqueous solution. The adsorption isotherms showed that Zn(II) adsorption can be better described using the Freundlich model than the Langmuir model. The maximum adsorption capacity of Zn(II) on GO determined using the Langmuir model at pH 7.0 and 293 K was 208.33 mg/g. The calculation of thermodynamic parameters revealed that the process of Zn(II) adsorption on GO was chemisorptions, endothermic, and spontaneous. Kinetic studies indicated that the pseudo-second-order kinetic model showed a better simulation of Zn(II) adsorption than the pseudo-first-order kinetic model. On the basis of surface complexation modeling, the double layer model provided a satisfactory prediction of Zn(II) by inner-sphere surface complexes (for example, SOZn+ and SOZnOH species), indicating that the interaction mechanism between Zn(II) and GO was mainly inner-sphere complexation. In terms of reusability, GO could maintain 92.23% of its initial capability after six cycles. These findings indicated that GO was a promising candidate for the immobilization and preconcentration of Zn(II) from aqueous solutions.

Preconcentration of Zn, Cu, and Ni Ions from Coffee Infusions via 8-Hydroxyquinoline Complexes on Graphene Prior to Energy Dispersive X-ray Fluorescence Spectrometry Determination.

A simple and effective preconcentration procedure based on dispersive micro solid-phase extraction prior to energy dispersive X-ray fluorescence spectrometric (EDXRF) determination of trace amounts of Ni, Cu, and Zn in coffee infusions was proposed. The method is based on the adsorption of 8-hydroxyquinoline metal complexes on micro amounts of graphene nanoparticles. In order to optimize adsorption process, the influence of some parameters such as pH, graphene mass, concentration of 8-hydroxyquinoline (8-HQ) and Triton X-100, sample volume, and sorption time were examined. At optimal preconcentration conditions, calibration curves were linear from 1 to 150 ng mL-1 for Ni and Cu and from 1 to 200 ng mL-1 for Zn. The recoveries of the metal ions were in the 95-98% range with the precision lower than 4.6%. The obtained detection limits were 0.08 ng mL-1 for Ni and 0.09 ng mL-1 for Cu and Zn. The proposed method was successfully applied to determination of Ni, Cu, and Zn in coffee infusions. Accuracy and repeatability of the proposed procedure were confirmed by the standard addition method and compared to the results obtained by ICP-OES technique.

Combined cation-exchange and solid phase extraction for the selective separation and preconcentration of zinc, copper, cadmium, mercury and cobalt among others using azo-dye functionalized resin

A facile synthesis of an ion exchange material (FSG-PAN) has been achieved by functionalizing silica gel with an azo-dye. Its composition and structure are well assessed by systematic analysis. Extractor possesses high BET surface area (617.794m(2)g(-1)), exchange capacity and break-through capacity (BTC) (Q0 Zn(II): 225; Cd(II): 918; Hg(II): 384, Cu(II): 269 and Co(II): 388μMg(-1)). The sorption process was endothermic (+ΔH), entropy-gaining (+ΔS) and spontaneous (-ΔG) in nature. Preconcentration factor has been optimized at 172(Zn(II)); 157.2(Cd(II)); 193.6(Hg(II)); 176(Cu(II)); 172.4(Co(II)). Density functional theory calculation has been performed to analyze the sorption pathway. BTC (μMg(-1)) of FSG-PAN was found to be the product of its frontier orbitals and state of sorbed metal ion species, x (at x=1, mononuclear and x>1, a polynuclear species; i.e., BTC=[amount of HOMO]×x). FSG-PAN is used for the selective separation and preconcentration of Zn(II), Cd(II), Hg(II), Cu(II),Co(II) from large volume sample (800mL) of low concentration (0.017-0.40mML(-1)) in presence of foreign ions (50-300mML(-1)) at optimum conditions (pH: 7.0±1.5, flow rate: 2.5mLmin(-1), temperature: 27°C, equilibration-time: 5min). The method was found to be effective for real samples also.

Pre-concentration and determination of zinc in water samples by ligand assisted pseudo stirbar hollow fiber solid/liquid phase microextraction

Abstract Pre-concentration and determination of Zn (II) across a ligand assisted pseudo stirbar hollow fiber solid/liquid phase microextraction method in water samples has been investigated. All detections were carried out by differential pulse anodic stripping voltammetry (DPASV). The method involves microextraction and pre-concentration of Zn (II) on the pseudo stir bar hollow fiber. Then desorption has been done using suitable solvent containing suitable ligand as complexing agent. The optimized conditions were obtained. The relationship between the peak current and concentration was linear over the range of 0.05–500 ng mL −1 . The limit of detection was 0.015 ng mL −1 . Under the optimized conditions, the pre-concentration factor is 5140. The applicability of the developed technique was evaluated by application to spiked, environmental water samples.

Determination of zinc in acacia honey by square wave stripping voltammetry with a bismuth-film-modified montmorillonite doped carbon paste electrode

In this study, a simple and environmentally friendly method for the determination of trace Zn(II) in honey is presented. The method was based on the preconcentration of Zn(II) on a bismuth-film-modified montmorillonite doped carbon paste electrode at −1.4 V and then the oxidation of Zn(II) by potential scan from −1.4 to 0 V using square wave stripping voltammetry. Experimental results illustrate that the sensitivity of the bismuth film electrode can be improved by a montmorillonite doped carbon paste electrode. Under optimal conditions, a linear range was observed for Zn(II) in the concentration range from 1 to 64 μg dm−3, and the detection limit of Zn(II) was 0.18 μg dm−3 with a 240-s deposition step. The proposed method was successfully applied to the determination of Zn(II) in honey samples. .

Preconcentration of Zn(II) from Sample Water by Phenyl-iminodiacetic Acid Grafted Multiwalled Carbon Nanotubes

: phenyl-iminodiacetic acid grafted multiwalled carbon nanotubes were prepared by grafted phenyl-iminodiacetic acid groups onto multi-walled carbon nanotubes via a diazotation reaction. The stability of chemically phenyl-iminodiacetic acid grafted multiwalled carbon nanotubes in concentrated hydrochloric acid which was then used as a recycling and pre-concentration reagent for further uses of phenyl-iminodiacetic acid grafted multiwalled carbon nanotubes. The application of this phenyl-iminodiacetic acid grafted multiwalled carbon nanotubes for sorption of a series of metal ions was performed by using different controlling factors such as the pH of metal ion solution and the equilibration shaking time by the static technique. Zn(II) was found to exhibit the highest affinity towards extraction by these phenyl-iminodiacetic acid grafted multiwalled carbon nanotubes phases. The pronounced selectivity was also confirmed from the determined distribution coefficient ( K d ) of all the metal ions, showing the highest value reported for Zn(II) to occur by phenyl-iminodiacetic acid grafted multiwalled carbon nanotubes. The potential applications of phenyl-iminodiacetic acid grafted multiwalled carbon nanotubes for selective extraction of Zn(II) to occur from aqueous solution were successfully accomplished as well as pre- concentration of low concentration of Zn(II) (60 pg ml -1 ) from natural tap water with a pre-concentration factor of 100 for Zn(II) off-line analysis by flame atomic absorption analysis.

The use of permeation liquid membranes for free zinc measurements in aqueous solution

Environmental context The free Zn ion concentration in environmental aqueous systems is an important factor in determining Zn deficiency or toxicity to organisms as this species is directly bioavailable. The permeation liquid membrane technique, a tool to measure either free or bioavailable metal concentrations in solution depending on its setup, was evaluated for the first time for Zn speciation in simplified plant nutrient solutions. The technique is low-cost and applicable to a broad range of aqueous samples. Abstract The bioavailability of Zn in environmental water phases strongly depends on its speciation. One important species in studies on Zn deficiency or toxicity to organisms is the free ion. The permeation liquid membrane (PLM) technique is a tool to measure free metal concentrations with a short analysis time of 1 h and at low cost. However, so far it has only been validated for Cd, Cu, Ni and Pb. In this study we tested the effect of carrier concentrations and pH on Zn transport across the organic PLM membrane and the ability of the technique to measure free Zn in synthetic plant nutrient solution. We found that Zn membrane transport is dependent on the concentration of the carrier molecule lauric acid (LA), whereas variations in the concentration of the other carrier molecule, the crown ether Kryptofix 22DD, showed no effect, suggesting that Zn is not transported by the ‘classical’ PLM transport mechanism by binding to the crown ether. Zn preconcentration increased with increasing pH and decreased with increasing ligand concentrations. Using 0.05 M LA, Zn membrane transport is expected to be rate limiting (permeability criterion <<1) and the free Zn concentration can be measured. Under these conditions, PLM measurements agreed well with speciation calculations and with Donnan membrane technique (DMT) measurements in the presence of ligands forming negatively charged Zn complexes (ethylenediaminetetraacetate or citrate). In the presence of L-histidine higher free Zn concentrations than calculated were measured by PLM and DMT, suggesting that positively charged complexes contributed to cross-membrane transport in both methods.

Synthesis of Magnetic Nanoparticles for Biological and Water Applications

ABSTRACT In the present work, a rapid and simple method based on magnetically assisted chemical separation has been described for analytical chemistry purposes. In this study, morin-modified magnetic nanoparticles were employed for separation and preconcentration of Zn(II) ions from water and biological samples. It combines the simplicity and the selectivity of solvent extraction with the simple separation of magnetic nanoparticles of the solution by utilizing magnet. The effect of different parameters, such as the amount of morin extractant loaded on the magnetic nanoparticles, pH of solution, adsorption time, and minimum amount of eluent required for elution of the zinc from the magnetic nanoparticles were evaluated. The limit of detection of the proposed method was 0.7 μgL−1. Also, the influence of interferences (various cationic and anionic) on the percent extraction of zinc was studied. The zinc ions were extracted from solution at pH of 5.2 and were desorbed from nanoparticles with 20 mL of CH3COOH:...

Synthesis and Characterization of New Chelating Resin Functionalized with Pyrocatechol Violet and its Application as Extractant for Zinc (II)

A new chelating resin, pyrocatechol violet (PV) immobilised on Amberlite XAD-4 polymeric matrix, was prepared. The resulting chelating resin has been characterised by elemental analysis, infrared (IR) spectra and textural analysis (BET). The resin was used for the preconcentration of Zn (II) prior to its determination by flame atomic absorption spectrometry (AAS). The optimization of experimental conditions during the quantitative extraction of Zn (II) by the resin phase was performed using factorial design including pH, amount of resin, and contact time. The phase exchange kinetic studies performed of Zn (II) revealed that equal 40 min was sufficient for reaching equilibrium metal ion sorption. Sorption is quantitative in the pH range of 5 – 5.5 (recovery 98 – 99%).

Preconcentration of Zn(II) in water samples using a new hybrid SBA-15-based material

A SBA-15 mesoporous silica has been chemically modified with 5-mercapto-1-methyltetrazole. The newly synthesized material (MTTZ-SBA-15) has been characterized, by powder X-ray diffraction, N(2) adsorption, FT-IR, (13)C NMR spectroscopy and elemental analysis, and used to preconcentrate Zn(II) in water samples. The effect of some variables on the adsorption capacity has been studied using the column techniques. The adsorption capacity of the prepared material followed the order: Zn>>Cu>Cd>>Mn, and under optimized conditions the maximum adsorption value for Zn(II) was 0.96+/-0.01 mmol/g with the adsorption efficiency of 0.76. In column experiments, adsorption was quantitative for 1000 mL of 7.65 x 10(-4)mM of Zn(II) solution and adsorbed ions were eluted out by 5 mL of 1M HCl (preconcentration factor of 200). Spiked tap water and mineral water were used for the preconcentration and determination of Zn(II) by flame atomic absorption spectrometry (FAAS), and a 102+/-2 and 98+/-3% recoveries were obtained. The LOD and LOQ values of the proposed method were found to be 8.0 x 10(-6) and 1.23 x 10(-5)mM, respectively. The relative standard deviation for four preconcentration experiments was found to be <or=4% in all cases.

Sensitive determination of terazosin by x‐ray fluorescence spectrometry based on the formation of ion‐pair associates with zinc thiocyanate

AbstractA new, simple and precise indirect method for the determination of terazosin through x‐ray fluorescence (XRF) is proposed. The method is based on the precipitation of an ion‐associate complex formed between terazosin and [Zn(SCN)4]2− and the formation of a thin film on a membrane filter. The optimum conditions for ion‐associate complex formation, such as pH, ionic strength, shaking time and stoichiometry of the complex, were studied. The complex was retained on the membrane filter, and the Zn Kα line was measured by XRF. The method presents the advantages of the separation of the drug from the matrix (excipients), the preconcentration of Zn, producing enhancement of XRF intensity though increased sensitivity, and the elimination of the matrix effects due to the thin film obtained. The lowest detection limit was 0.732 µg ml−1. The validation studies were realized by the related applications and the results were evaluated statistically. The method was successfully applied to terazosin determination in tablets or in bulk. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Recovery of molybdenum and cobalt powders from spent catalysts : M.A.Rabah et al. (CMRDI, Helwan, Cairo, Egypt.) Powder Metall., vol 40, no 4, 1997, 283–288

A facile synthesis of an ion exchange material (FSG–PAN) has been achieved by functionalizing silica gel with an azo-dye. Its composition and structure are well assessed by systematic analysis. Extractor possesses high BET surface area (617.794 m2 g−1), exchange capacity and break-through capacity (BTC) (Q0 Zn(II): 225; Cd(II): 918; Hg(II): 384, Cu(II): 269 and Co(II): 388 μM g−1). The sorption process was endothermic (+ΔH), entropy-gaining (+ΔS) and spontaneous (−ΔG) in nature. Preconcentration factor has been optimized at 172(Zn(II)); 157.2(Cd(II)); 193.6(Hg(II)); 176(Cu(II)); 172.4(Co(II)). Density functional theory calculation has been performed to analyze the sorption pathway. BTC (μM g−1) of FSG–PAN was found to be the product of its frontier orbitals and state of sorbed metal ion species, x (at x = 1, mononuclear and x > 1, a polynuclear species; i.e., BTC = [amount of HOMO] × x). FSG–PAN is used for the selective separation and preconcentration of Zn(II), Cd(II), Hg(II), Cu(II),Co(II) from large volume sample (800 mL) of low concentration (0.017–0.40 mM L−1) in presence of foreign ions (50–300 mM L−1) at optimum conditions (pH: 7.0 ± 1.5, flow rate: 2.5 mL min−1, temperature: 27 °C, equilibration-time: 5 min). The method was found to be effective for real samples also.