Preconcentration and Determination of Trace Amounts of Heavy Metals in Water Samples Using Membrane Disk and Flame Atomic Absorption Spectrometry

A fast and simple method for preconcentration of Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋ from natural water samples was developed. The metal ions were complexed with sodium diethyldithiocarbamate （Na-DDTC）, then adsorbed onto octadecyl silica membrane disk, recovered and determined by FAAS. Extraction efficiency, influence of sample volume and eluent flow rates, effects of pH, amount of Na-DDTC, nature and amount of eluent for elution of metal ions from membrane disk, break through volume and limit of detection have been evaluated. The effect of foreign ions on the percent recovery of heavy metal ions has also been studied. The limit of detection of the proposed method for Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋was found to be 2.03, 0.47, 3.13, 0.44, 1.24 and 2.05 ng·mL^-1, respectively. The proposed （DDTC） method has been successfully applied to the recovery and determination of heavy metal ions in different water samples.     

Chemically bonded multiwalled carbon nanotubes as efficient material for solid phase extraction of some metal ions in food samples

Multiwalled carbon nanotubes chemically functionalized with 2-((3-silylpropylimino) methyl) phenol (SPIMP-MWCNT) and successfully applied for the solid phase extraction (SPE) of some metal ions in food samples. The influences of the analytical parameters including pH, amounts of solid phase, eluent conditions (type, volume and concentrations), sample volume and interference of some metal ions on the recoveries of ions Cu²⁺, Pb²⁺, Fe²⁺, Ni²⁺ and Zn²⁺ ion were investigated. The metal ions retained on SPIMP-MWCNT was eluted using 6?mL of 4?mol?L^?1 HNO₃ solution and their content was determined by flame atomic absorption spectrometry (FAAS) with recoveries more than 95% and relative standard deviations (n?=?5) between 2.4–3.4% for both reproducibility and repeatability. The detection limit of this metal ions was between 1.0–2.6?ng?mL^?1 (3S _b , n?=?10) and their preconcentration factor was 100, while their loading capacity was above 32.9?mg?g^?1 of SPIMP-MWCNT. The proposed method was successfully applied for the preconcentration and determination of analytes in different samples.     

Effect of dimensions of multi-walled carbon nanotubes on its enrichment efficiency of metal ions from environmental waters

The effect of dimensions (length and external diameter) of multi-walled carbon nanotubes (MWCNTs) on its preconcentration efficiency towards some metal ions (Pb²⁺, Cd²⁺, Cu²⁺, Zn²⁺ and MnO₄⁻) from environmental waters prior to their analysis by flame atomic absorption spectroscopy (FAAS) was investigated. MWCNTs (as-received from the manufacturer) of various external diameters and lengths were involved. Other variables optimized included effects of pH of water sample, composition and volume of eluent, mass of the MWCNTs, breakthrough volume and coexisting ions. Maximum recovery of metal ions was obtained at pH 9 where it was thought that precipitation of metals as their hydroxides played the major factor in metals uptake by MWCNT. It was suggested that the use of appropriate dimensions of MWCNTs may support the trapping process of the precipitated metal hydroxides by MWCNTs. It was found that long MWCNT of length 5-15 μm and external diameter 10-30 nm gave the highest enrichment efficiency towards almost all the targeted metal ions. It could be used for preconcentration of MnO₄⁻, Cu²⁺, Zn²⁺ and Pb²⁺ with almost full recovery; but not for Cd²⁺ due to its low recovery. The optimized solid phase extraction (SPE) procedure was capable of determining metal ions in the linear range 20-100 ng mL⁻¹ (except for Zn²⁺ from 20 to 150 ng mL⁻¹). Detection limits were 0.709 ng mL⁻¹ for MnO₄⁻, 0.278 ng mL⁻¹ for Pb²⁺, 0.465 ng mL⁻¹ for Cu²⁺, 0.867 ng mL⁻¹ for Zn²⁺. Application of the optimized SPE procedure to environmental waters (tap water, reservoir water and stream water) gave spike recoveries of the metals in the range of 81-100%.     

A novel method for the simple and simultaneous preconcentration of Pb2+, Cu2+ and Zn2+ ions with aid of diethylenetriamine functionalized SBA-15 nanoporous silica compound

A rapid method for the extraction and monitoring of nanogram level of Pb²⁺, Cu²⁺ and Zn²⁺ ions using uniform silanized mesopor (SBA-15) functionalized with diethylenetriamine groups and flame atomic absorption spectrometry (FAAS) is presented. The preconcentration factor of the method is 100 and detection limit of the technique is 5.5?ng?mL^?1 and 1.4?ng?mL^?1 and 0.1?ng?mL^?1 for Pb²⁺, Cu²⁺ and Zn²⁺ respectively. The time and the optimum amount of the sorbent, pH and minimum amount of acid for stripping of ions from functionalized SBA-15 were tested. The maximum capacity the functionalized SBA-15 was found to be 183.0 (±1.9) µg, 156.0 (±1.5) µg and 80.0 (±1.6) µg of Pb²⁺, Cu²⁺ and Zn²⁺/mg functionalized SBA-15, respectively.     

Solid phase extraction of heavy metals on chemically modified silica-gel with 2-(3-silylpropylimino) methyl)-5-bromophenol in food samples

Trace amounts of Fe³⁺, Pb²⁺, Cu²⁺, Ni²⁺, Co²⁺ and Zn²⁺ ions were efficiently enriched following complexation with silica-gel chemically functionalized with 2-((3-silylpropylimino)methyl)-5-bromophenol. The enriched metal ions efficiently eluted with 6?mL of 4.0?mol?L^?1 nitric acid and their metal contents were determined by flame atomic absorption spectrometry (FAAS). The influences of the analytical parameters and experimental variables on the recoveries of the metal ions under study were investigated and optimized. The method has high sorption preconcentration efficiency even in the presence of various interfering ions. At optimum values of all variables the method is applicable for analysis of real samples with recoveries in the range of 95 to 105% with RSD lower than 4.2% and detection limits between 1.4 and 2.8?µg?L^?1.     

Preconcentration and Determination of Copper(II) by Novel Solid-Phase Extraction and High-Resolution Continuum Source Flame Atomic Absorption Spectrometry

Amberlite XAD-4 modified with N-para-anisidine-3,5-di-tert-butylsalicylaldimine was investigated as a new chealting sorbent for the selective separation and preconcentration of Cu(II). The metal ion was retained by chemical sorption on the modified resin, eluted by hydrochloric acid, and determined by high-resolution continuum source flame atomic absorption spectrometry. The prepared resin was characterized for the solid-phase extraction of Cd²⁺, Co²⁺, Cr³⁺, Cu²⁺, Fe³⁺, Mn²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ in a column. The influence of the pH, the mass of solid phase, eluent, flow rate, and sample volume was optimized. Using the optimum conditions, only Cu(II) showed quantitative sorption at the 95% confidence level, and the recoveries of the other metal ions were below 80%. A preconcentration factor 125 was obtained for Cu(II) with a limit of detection of 0.56?µg?L^?1. The method was used for the determination of Cu(II) in tap water, river water, tomato leaves, and fish. The relative standard deviation and the relative error were lower than 7%.     

Amberlite XAD-7 resin impregnated with 2-(1-(4-chlorophenyl)-4,5-diphenyl-1H-imidazol-2yl)-4-nitrophenol for enrichment of metal ions

The Amberlite XAD-7 resin modification was carried out by loading 2-(1-(4-chlorophenyl)-4,5-diphenyl-1H-imidazol-2yl)-4-nitrophenol (CPDPINP). Subsequently, this new sorbent was applied for the enrichment of metal ions such as Cu²⁺, Ni²⁺, Co²⁺ Zn²⁺ and Pb²⁺ ions. The effect of various parameters on their sorption and following recoveries was studied in column procedure. The preconcentrated ions were eluted by appropriate eluent and their contents were quantified by FAAS. This method has preconcentration factor of 150 and enrichment factor in the range of 20.8–29.1. At optimum values of all variables, the proposed method has linear calibration graphs in the range of 0.01 up to 0.29 μg mL⁻¹ with detection limit (3SDb/m, n = 15) between 1.6 and 2.6 ng mL⁻¹. This protocol is usable for successful analysis of Cu²⁺, Ni²⁺, Co²⁺ Zn²⁺ and Pb²⁺ ions in different matrices with reasonable recoveries (>93%) and acceptable relative standard deviation (<4.7%).     

Complexing properties of cation-exchangers grafted with carboxyl moieties

The complexing properties of CM-52, Olvagel-COOH, MacroPrep 50 CM, and hypercrosslinked polystyrene MN (carboxyl-grafted sorbents) toward Cu²⁺, Co²⁺, Ni²⁺, Cd²⁺, Zn²⁺, Mn²⁺, and Pb²⁺ have been studied. The optimal parameters for the sorption of these metal ions from solution have been determined. The pH effect on the ion uptake has been studied. The uptake is maximal at pHs higher than 5–6. When pH is lower than 2, the indicated ions are quantitatively desorbed. Olvagel-COOH is most selective toward these ions.     

Application of Cloud Point Extraction for Copper,Nickel, Zinc and Iron Ions in Environmental Samples

A cloud point extraction procedure was presented for the preconcentration of copper, nickel, zinc and iron ions in various samples. After complexation by 2‐(6‐(1H‐benzo[d]imidazol‐2‐yl)pyridin‐2‐yl)‐1H‐benzo[d]Imidazole (BIYPYBI), analyte ions are quantitatively extracted in Triton X‐114 following centrifugation. 1.0 mol L^?1 HNO₃ nitric acid in methanol was added to the surfactant‐rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). The adopted concentrations for BIYPYBI, Triton X‐114 and HNO₃ and bath temperature, centrifuge rate and time were optimized. Detection limits for Cu²⁺, Fe³⁺, Zn²⁺ and Ni²⁺ ions was 1.4, 2.2, 1.0 and 1.9 ng mL^?1, respectively. The preconcentration factors for all ions was 30, while the enrichment factor of Cu²⁺, Fe³⁺, Zn²⁺ and Ni²⁺ ions was 35, 25, 39 and 30, respectively. The proposed procedure was applied to the analysis of real samples.     

Selective separations by reactive ion exchange: Part 4. Preconcentration of cadmium and zinc by in situ precipitation as hexacyanoferrate(II) salts on gel and macroporous ion-exchange resins

The in situ precipitation of traces of cadmium(II) and zinc(II) ions as hexacyanoferrates from aqueous matrices was studied on conventional polystyrene gel and macroporous cation- and anion-exchange resins. Coprecipitation with each other or with copper(II) ions present in binary cation resins or in solution, and the influence of added nonprecipitating ions of the same charge type such as magnesium(II) were investigated. Microporous (gel) cation exchangers gave reasonable recoveries and macroporous cation exchangers gave very good recoveries; but macroporous anion exchangers performed best, suggesting macroporous hexacyanoferrate(II) resin as an ideal phase for collection/preconcentration of traces of Cu²⁺, Cd²⁺, Zn²⁺, and possibly Co²⁺, Ni²⁺, and Pb²⁺ from waters. As expected, very low yields were obtained with conventional anion exchange resin in the hexacyanoferrate form. Uniform distribution of Cu²⁺, Zn²⁺, and Cd²⁺ over macroporous anion-exchange resin phases were established by means of electron probe scans and taken as evidence for the formation of a uniform, well-developed precipitate layer covering the entire resin particle surface.     

Chemically modified activated carbon with S-benzyldithiocarbazate as a new solid-phase extractant for preconcentration of mercury prior to ICP-AES determination

A new sorbent S-benzyldithiocarbazate (SBDTC) modified activated carbon (AC-SBDTC) was prepared and studied for preconcentration for trace mercury(II) prior to inductively coupled plasma atom emission spectrometry (ICP-AES). The experimental conditions were optimised with respect to different experimental parameters using both batch and column procedures in detail. The optimum pH value for the separation of Hg(II) on the new sorbent was 3, while the adsorption equilibrium was achieved in less than 5?min. Complete elution of the adsorbed metal ions from the sorbent surface was carried out using 5?mL of 0.25?mol?L^?1 of HCl and 2% CS(NH₂)₂. Common coexisting ions did not interfere with the determination. The maximum static adsorption capacity of the sorbent under optimum conditions was found to be 0.55?mmol?g^?1. The detection limit of the present method was found to be 0.09?ng?mL^?1, and the relative standard deviation (RSD) was lower than 2.0%. The procedure was validated by analysing the certified reference river sediment material (GBW 08301, China), the results obtained were in good agreement with standard values. This sorbent was successfully employed in the separation and preconcentration of trace Hg(II) from the natural water samples yielding 80-fold concentration factor.     

Conductometric studies and application of new Schiff base ligand as carbon paste electrode modifier for mercury and cadmium determination

A new chemically modified carbon paste electrode by 2,2?-((pyridine-2,6-diylbis(azanylylidene))bis(methanylylidene))diphenol (L) ligand has been made and used as a sensor for determination of trace mercury and cadmium ions with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. Complexation studies of the ligand with Cu²⁺, Zn²⁺, Hg²⁺, Ni²⁺ and Cd²⁺ ions by conductometric method in acetonitrile–ethanol mixture at 25°C show that the ML complexes have formed. The formation constants of complexes were calculated from the computer fitting of the molar conductance–mole ratio data, and the stability of the resulting complexes varied in order of Cd²⁺ > Hg²⁺ > Cu²⁺ > Zn²⁺ > Ni²⁺. Then a simple and effective chemically modified carbon paste electrode with L was prepared, and the electrochemical properties and applications of the modified electrode were investigated. Under the optimal conditions, the detection limit was 0.0494 μg L^?1 and 0.0782 μg L^?1 for cadmium and mercury ions, respectively, and the linear range for both metal ions were from 1 to 100 μg L^?1. The electrode shows high sensitivity, reproducibility and low cost, and was successfully applied to determination of Cd²⁺ and Hg²⁺ ions in water samples with recovery in the range of 97–101%.     

Simultaneous Titration of Ternary Mixtures of Pb(II), Cd(II) and Cu(II) with Potentiometric Electronic Tongue Detection

An automatic titration method is reported to resolve ternary mixtures of transition metals (Pb²⁺, Cd²⁺ and Cu²⁺) employing electronic tongue detection and a reduced number of pre‐defined additions of EDTA titrant. Sensors used were PVC membrane selective electrodes with generic response to heavy‐metals, plus an artificial neural network response model. Detection limits obtained were ca. 1 mg L^?1 for the three target ions and reproducibilities 3.0 % for Pb²⁺, 4.1 % for Cd²⁺ and 5.2 % for Cu²⁺. The system was applied to contaminated soil samples and high accuracy was obtained for the determination of Pb²⁺. In the determination Cd²⁺ and Cu²⁺, sample matrix showed a significant effect.     

Synthesis,structure, and solvent-extraction properties of tridentate oxime ligands and their cobalt(II), nickel(II), copper(II), zinc(II) complexes

Synthesis of four different types of ligands Ar[COC(NOH)R] _n (Ar = biphenyl, n = 1, HL¹; Ar = biphenyl, n = 2, H₂L²; Ar = diphenylmethane, n = 1, HL³; Ar = diphenylmethane, n = 2, H₂L⁴; R = furfurylamine in all ligands) and their dinuclear Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ complexes is reported herein. These compounds were characterized by elemental analysis, ICP-OES, FT-IR spectra, and magnetic susceptibility measurements. The ligands were further characterized by ¹H NMR. The results suggest that dinuclear complexes of HL¹ and HL³ have a metal to ligand mole ratio of 2: 2 and dinuclear complexes H₂L² and H₂L⁴ have a metal to ligand mole ratio of 2: 1. Square pyramidal or octahedral structures are proposed for complexes of oxime ligands. Furthermore, extraction abilities of the four ligands were also evaluated in chloroform using selected transition metal picrates such as Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺. The ligands show strong binding ability towards Hg²⁺ and Cu²⁺ ions.     

Study of the interaction of mono-, di-, and trisubstituted sodium orthophosphates with thermally activated dolomite

Interaction of dolomite thermally treated at 800°C with solutions of mono-, di-, and trisubstituted sodium phosphate was studied. It was shown that thermally treated dolomite binds 0.75 to 3.0 mmol g^–1 of phosphorus, depending on the nature of a phosphating reagent, and the interaction mostly occurs with magnesium oxide, which enables use of this kind of dolomite as a sorbent of phosphate ions. It was found that the nature of the phosphating reagent affects the chemical and phase composition of the materials obtained, as well as their sorption properties with respect to heavy metal ions. The products formed in acid-free phosphation of dolomite have high sorption capacity, from 1.5 to 6.8 mmol g^–1 for Pb²⁺, Zn²⁺, Cu²⁺, Cd²⁺, Ni²⁺, Sr²⁺, and Co²⁺ ions, which enables their use as effective sorbents for heavy metal ions.urning.     

Interaction of a Schiff-base fluorescent sensor with Al3+: experimental and computational studies

A fluorescent Al³⁺ chemo-sensor, 1-phenyl-3-methyl-5-hydroxypyrazole-4-acetone-(3′,4′-dimethylpyrrole-2′-formyl) hydrazone (L), has been synthesized and characterized. L can detect Al³⁺ in ethanol solution with a significant fluorescence enhancement of a turn-on ratio over 155-fold due to the formation of a 1?:?1 complex which is based on the molar ratio between L and Al³⁺ ions, and the 1?:?1 stoichiometric complexation can be obtained from density functional theory calculations. No significant interference of other metal ions such as Na⁺, K⁺, Mg²⁺, Ca²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe³⁺, Cr³⁺, Pb²⁺, and Ag⁺ was found. The detection limit for Al³⁺ was 5?×?10^?9?M in ethanol.     

On-line trace metal enrichment and matrix isolation in atomic absorption spectrometry by a column containing immobilized 8-quinolinol in a flow-injection system

Metal ions (Cu²⁺, Co²⁺, Cd²⁺, Ni²⁺, Pb²⁺, Zn²⁺) were concentrated quantitatively and isolated from the sample matrix by a colum     

Structural and sorption characteristics of carbon adsorbents from waste formed in wood processing

The structural and sorption characteristics of microporous sorbents from industrial lignin with respect to some toxic substances, Pb²⁺, Cd²⁺, Cu²⁺, and NH⁺ ₄ ions, and also the possibility of accumulation of methane on these carbons were studied. Simple procedures for modification of the carbon surface to improve the sorption power of the carbons were suggested.     

Spectrophotometric study of complexation of dibenzopyridino-18-crown-6 with some transition and post-transition metal ions in DMSO solution using murexide as a metallochromic ligand

The complexation reaction of dibenzopyridino-18-crown-6 (DBPY 18C6) with Co²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Hg²⁺, and Ag⁺ have been studied in DMSO at 25°C by the spectrophotometric method. Murexide was used as a competitive colored ligand. The stoichiometry of metal ion-murexide and metal ions with DBPY18C6 complexes were estimated by mole ratio and continuous variation methods and emphasized by the KINFIT program. The stoichiometry of all the complexes was found to be 1: 1 (metal ion/ligand). The order of stability constants for the obtained metal ion-murexide complexes (1: 1) varies in the order Cu²⁺ > Cd²⁺ > Co²⁺ ∼ Pb²⁺ > Zn²⁺ > Ag⁺ > Hg²⁺. This trend shows that the transition metal ions clearly obey the Irving-Williams role. For the post-transition metal ions, the ionic radius and soft-hard behavior was the major affects in varying of this order. The dibenzopyridino-18-crown-6 complexes with the used metal ions vary as Ag⁺ > Pb²⁺ > Cu²⁺ > Cd²⁺ > Hg²⁺ > Zn²⁺ > Co²⁺. The article is published in the original.     

Synthesis of a Dithiocarbamate Chelate Resin and Its Oxidized form and Their Adsorption Properties for Heavy Metal Ions

A series of macroporous dithiocarbamate chelate resins, III and V, and an oxidized resin, VI, with high adsorption capacity were prepared. The influence of various reaction conditions of amination, dithiocarboxylation, and oxidation were examined. The structure and the conversion of functional groups of resins were confirmed by IR spectra and elemental analysis. The adsorption capacities of Resin II for Hg²⁺, Cu²⁺, Zn²⁺, and Cd²⁺ are 4.40, 2.44, 1.77, and 1.36 mmol/g, respectively. The adsorption capacities of Resins V and VI for Cu²⁺. Zn²⁺, Ni²⁺, Co³⁺, Ag⁺, Hg²⁺, Cd²⁺, Pb²⁺, and Au³⁺ are 4.07–0.51 and 3.81–0.59 meq ion/g, respectively. The adsorption rate and the influence of pH on the adsorption percentage of the resins for metal ions were examined. Noble metal, transitional metal, and heavy metal ions can be quantitatively adsorbed by the resins. The adsorbed Cu²⁺, Pb²⁺, Cd²⁺, Co³⁺, and Ni²⁺ can be quantitatively eluted with 5N HNO₃, and the presence of large amounts of Ca²⁺, Mg²⁺, Fe³⁺, and Al³⁺ did not interfere.