Preparation of novel ion exchange polyurethane foam and its application for separation and determination of palladium in environmental samples

The new strong anion exchanger (PUFIX) from polyurethane foam was prepared by coupling of the primary amine of the foam matrix with ethyl iodide. PUFIX was characterized using different tools (IR spectra, elemental analysis, density and thermal analysis). The sorption properties of the new anion exchanger (PUFIX) and chromatographic behaviour for separation and determination of palladium(II) ions at low concentrations from aqueous iodide or thiocyanate media were investigated by a batch and dynamic processes. The maximum sorption of Pd(II) was in the pH range of 0.3–2. The kinetics of sorption of the Pd(II) by the PUFIX was found to be fast with average values of half-life of sorption (t_1/2) of 3.32 min. The variation of the sorption of Pd(II) with temperature gives average values of ΔH, ΔS, ΔG and ΔE to be −38.3 kJ mol⁻¹, −100.7 J K⁻¹ mol⁻¹, −8.3 and 11.8 kJ mol⁻¹, respectively. The sorption capacity of PUFIX was 1.69 mmol g⁻¹ for Pd(II), preconcentration factors of values ≈250 and the recovery 99–100% were achieved (R.S.D. ≈ 1.24%). The lower detection limit, 1.28 ng mL⁻¹ was evaluated using spectrophotometric method (R.S.D. ≈ 2.46%).     

The efficacy of nitrosonaphthol functionalized XAD-16 resin for the preconcentration/sorption of Ni(II) and Cu(II) ions

Amberlite XAD-16 resin has been functionalized using nitrosonaphthol as a ligand and characterized employing elemental, thermogravimetric analysis and FT-IR spectroscopy. The sorption of Ni(II) and Cu(II) ions onto this functionalized resin is investigated and optimized with respect to the sorptive medium (pH), shaking speed and equilibration time between liquid and solid phases. The monitoring of the influence of diverse ions on the sorption of metal ions has revealed that phosphate, bicarbonate and citrate reduce the sorption up to 10–14%. The sorption data followed Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) isotherms. The Freundlich parameters computed are 1/n = 0.56 ± 0.03 and 0.49 ± 0.05, A = 9.54 ± 1.5 and 6.0 ± 0.5 mmol g⁻¹ for Ni(II) and Cu(II) ions, respectively. D–R isotherm yields the values of X_m = 0.87 ± 0.07 and 0.35 ± 0.05 mmol g⁻¹ and of E = 9.5 ± 0.23 and 12.3 ± 0.6 kJ mol⁻¹ for Ni(II) and Cu(II) ions, respectively. Langmuir characteristic constants estimated are Q = 0.082 ± 0.005 and 0.063 ± 0.003 mmol g⁻¹, b = (4.7 ± 0.2) × 10⁴ and (7.31 ± 0.11) × 10⁴ l mol⁻¹ for Ni(II) and Cu(II) ions, respectively. The variation of sorption with temperature gives thermodynamic quantities of ΔH = −58.9 ± 0.12 and −40.38 ± 0.11 kJ mol⁻¹, ΔS = −183 ± 10 and −130 ± 8 J mol⁻¹ K⁻¹ and ΔG = −4.4 ± 0.09 and −2.06 ± 0.08 kJ mol⁻¹ at 298 K for Ni(II) and Cu(II) ions, respectively. Using kinetic equations, values of intraparticle transport and of first order rate constant have been computed for both the metal ions. The sorption procedure is utilized to preconcentrate these ions prior to their determination in tea, vegetable oil, hydrogenated oil (ghee) and palm oil by atomic absorption spectrometry using direct and standard addition methods.     

Pyrocatechol Violet immobilized Amberlite XAD-2: synthesis and metal-ion uptake properties suitable for analytical applications

Amberlite XAD-2 has been functionalized by coupling it, through the ---N=N--- group, with Pyrocatechol Violet (PV), and the resulting resin has been characterized by elemental analysis, thermogravimetric analysis (TGA) and IR spectra. The resin has been used for preconcentrating Zn(II), Cd(II), Pb(II) and Ni(II) ions prior to their determination by flame atomic absorption spectrometry. The optimum pH values for quantitative sorption are 5, 5–7, 4, and 3 for Zn, Cd, Pb and Ni, respectively. The four metals can be desorbed (recovery ˜98%) with 4 M HNO₃; also, 4 M HCl is equally suitable except for Zn. The sorption capacity of the resin is 1410, 1270, 620 and 1360 μg g⁻¹ resin for Zn, Cd, Ni and Pb, respectively. The effect of F⁻, Cl⁻, NO₃⁻, SO₄²⁻ and PO₄³⁻ on the sorption of these four metal ions has been investigated. They are tolerable in the range 0.01–0.20 M, for Pb. In the sorption of Zn(II) and Ni(II), the tolerance limits of all these ions are upto 0.01 M, whereas for Cd(II), F⁻, NO₃⁻, and PO₄³⁻ have been found to be tolerable upto 0.50, 0.10 and 0.10 M, respectively. The preconcentration factors are 60, 50, 23 and 18 for Zn, Cd, Pb and Ni, respectively. Simultaneous collection and determination of the four metals are possible. Cations commonly present in drinking water do not affect the sorption of either metal ion if present at a concentration level similar to that of water. The method has been applied to determine Zn, Ni and Pb content of well-water samples (RSD ≤9%).     

Cellulose based macromolecular chelator having pyrocatechol as an anchored ligand: synthesis and applications as metal extractant prior to their determination by flame atomic absorption spectrometry

Pyrocatechol is immobilized on cellulose via ---NH---CH₂---CH₂---NH---SO₂---C₆H₄---N=N--- linker and the resulting macromolecular chelator characterized by IR, TGA, CPMAS ¹³C NMR and elemental analyses. It has been used for enrichment of Cu(II), Zn(II), Fe(III), Ni(II), Co(II), Cd(II) and Pb(II) prior to their determination by flame atomic absorption spectrometry (FAAS). The pH ranges for quantitative sorption (98.0–99.4%) are 4.0–7.0, 5.0–6.0, 3.0–4.0, 5.0–7.0, 5.0–8.0, 7.0–8.0 and 4.0–5.0, respectively. The desorption was found quantitative with 0.5 mol dm⁻³ HCl/HNO₃ (for Pb). The sorption capacity of the matrix for the seven metal ions has been found in the range 85.3–186.2 μmol g⁻¹. The optimum flow rate of metal ion solution for quantitative sorption of metal onto pyrocatechol functionalized cellulose as determined by column method, is 2–6 cm³ min⁻¹, whereas for desorption it is 2–4 cm³ min⁻¹. The tolerance limits for NaCl, NaBr, NaI, NaNO₃, Na₂SO₄, Na₃PO_4, humic acid, EDTA, ascorbic acid, citric acid, sodium tartrate, Ca(II) and Mg(II) in the sorption of all the seven metal ions are reported. Ascorbic acid is tolerable up to 0.8 mmol dm⁻³ with Cu and Pb where as sodium tartrate does not interfere up to 0.6 mmol dm⁻³ with Pb. There is no interference of NaBr, NaCl and NaNO₃ up to a concentration of 0.5 mol dm⁻³, in the sorption of Cu(II), Cd(II) and Fe(III) on to the chelating cellulose matrix The preconcentration factors are between 75 and 300 and t_1/2 values ≤5 min for all the metal ions. Simultaneous sorption of Cu, Zn, Ni and Co is possible at pH 5.0 if their total concentration does not exceed lowest sorption capacity. The present matrix coupled with FAAS has been used to enrich and determine the seven metal ions in river and tap water samples (relative standard deviation (R.S.D.) 1.05–7.20%) and synthetic certified water sample SLRS-4 (NRC, Canada) with R.S.D. 2.03%. The cobalt present in pharmaceutical vitamin tablets was also preconcentrated on the modified cellulose and determined by FAAS (R.S.D. 1.87%).     

8-Hydroxyquinoline anchored to silica gel via new moderate size linker: synthesis and applications as a metal ion collector for their flame atomic absorption spectrometric determination

The silica gel modified with (3-aminopropyl-triethoxysilane) was reacted with 5-formyl-8-hydroxyquinoline (FHOQ_x) to anchor 8-quinolinol ligand on the silica gel. It was characterised with cross polarisation magic angle spinning (CPMAS) NMR and diffuse reflectance infrared Fourier transformation (DRIFT) spectroscopy and used for the preconcentration of Cu(II), Pb(II), Ni(II), Fe(III), Cd(II), Zn(II) and Co(II) prior to their determination by flame atomic absorption spectrometry. The surface area of the modified silica gel has been found to be 227 m² g⁻¹ and the two pKa values as 3.8 and 8.0. The optimum pH ranges for quantitative sorption are 4.0–7.0, 4.5–7.0, 3.0–6.0, 5.0–8.0, 5.0–8.0, 5.0–8.0 and 4.0–7.0 for Cu, Pb, Fe, Zn, Co, Ni and Cd, respectively. All the metals can be desorbed with 2.5 mol l⁻¹ HCl or HNO₃. The sorption capacity for these metal ions is in range of 92–448.0 μmol g⁻¹ and follows the order Cd3, NaCl, NaBr, Na₂SO₄ and Na₃PO₄, glycine, sodium citrate, EDTA, humic acid and cations Ca(II), Mg(II), Mn(II) and Cr(III) in the sorption of all the seven metal ions are reported. The preconcentration factors are 150, 250, 200, 300, 250, 300 and 200 for Cd, Co, Zn, Cu, Pb, Fe and Ni, respectively and t_1/2 values <1 min except for Ni. The 95% extraction by batch method takes ≤25 min. The simultaneous enrichment and determination of all the metals are possible if the total load of the metal ions is less than sorption capacity. In river water samples all these metal ions were enriched with the present ligand anchored silica gel and determined with flame atomic absorption spectrometer (R.S.D.≤6.4%). Cobalt contents of pharmaceutical samples (vitamin tablet) were preconcentrated with the present chelating silica gel and estimated by flame AAS, with R.S.D.1.4%. The results are in the good agreement with the certified value, 1.99 μg g⁻¹ of the tablets. Iron and copper in certified reference materials (synthetic) SLRS-4 and SLEW-3 have been enriched with the modified silica gel and estimated with R.S.D.<5%.     

A new chelating sorbent for metal ion extraction under high saline conditions

A new chelating polymeric sorbent was developed by functionalizing Amberlite XAD-16 with 1,3-dimethyl-3-aminopropan-1-ol via a simple condensation mechanism. The newly developed chelating matrix offered a high resin capacity and faster sorption kinetics for the metal ions such as Mn(II), Pb(II), Ni(II), Co(II), Cu(II), Cd(II) and Zn(II). Various physio-chemical parameters like pH-effect, kinetics, eluant volume and flow rate, sample breakthrough volume, matrix interference effect on the metal ion sorption have been studied. The optimum pH range for the sorption of the above mentioned metal ions were 6.0–7.5, 6.0–7.0, 8.0–8.5, 7.0–7.5, 6.5–7.5, 7.5–8.5 and 6.5–7.0, respectively. The resin capacities for Mn(II), Pb(II), Ni(II), Co(II), Cu(II), Cd(II) and Zn(II) were found to be 0.62, 0.23, 0.55, 0.27, 0.46, 0.21 and 0.25 mmol g⁻¹ of the resin, respectively. The lower limit of detection was 10 ng ml⁻¹ for Cd(II), 40 ng ml⁻¹ for Mn(II) and Zn(II), 32 ng ml⁻¹ for Ni(II), 25 ng ml⁻¹ for Cu(II) and Co(II) and 20 ng ml⁻¹ for Pb(II). A high preconcentration value of 300 in the case of Mn(II), Co(II), Ni(II), Cu(II),Cd(II) and a value of 500 and 250 for Pb(II) and Zn(II), respectively, were achieved. A recovery of >98% was obtained for all the metal ions with 4 M HCl as eluting agent except in the case of Cu(II) where in 6 M HCl was necessary. The chelating polymer showed low sorption behavior to alkali and alkaline earth metals and also to various inorganic anionic species present in saline matrix. The method was applied for metal ion determination from water samples like seawater, well water and tap water and also from green leafy vegetable, from certified multivitamin tablets and steel samples.     

Synthesis, structure, and fluorescence of two cadmium(II)-citrate coordination polymers with different coordination architectures

Two novel Cd(II)-citrate complexes were obtained with different metal/ligand ratios through hydrothermal method. Their structures were determined by single-crystal X-ray diffraction analysis. Although their topological structures are both 2-D layer network assemblies, both central Cd(II) ions and Hcit³⁻ ligands display completely different coordination modes. In polymeric complex 1, Hcit³⁻ serves as a μ₁₀-bridged and central Cd(II) ions adopt 6- and 8-coordinated configurations. In contrast, a μ₉-bridged and 6- and 7-coordinated environments between Cd(II) and Hcit³⁻ are established in the polymeric complex 2. Two Complexes remain stable up to approximately 300 °C. The complex 1 exhibits strong fluorescent emission band at 450 nm (λ=346 nm) as well as complex 2 exhibits strong fluorescent emission band at 430 (λ=346 nm).     

Extraction of Pb(II), Cd(II), and Hg(II) from aqueous solution by nitrogen and thiol functionality grafted to silica gel measured by calorimetry

The reaction of ethylene sulfide with 3-aminopropyltrimethoxysilane gave a new silylating agent, which was anchored onto a silica surface via the sol–gel procedure. This surface displayed a chelating moiety containing nitrogen and two sulfur basic centers potentially capable of extracting cations from aqueous solutions. The process of metal extraction was followed by a batch method, and fitted to a modified Langmuir equation. The maximum adsorption capacities found were: 2.06 ± 0.01, 3.72 ± 0.02, and 5.14 ± 0.02 mmol g⁻¹ for Pb(II), Cd(II), and Hg(II), respectively. The enthalpies of bending are: −1.16 ± 0.04, −3.60 ± 0.10, and −8.94 ± 0.03 kJ mol⁻¹ for Cd(II), Pb(II), and Hg(II), respectively. The Gibbs free energies of binding agree with the spontaneity of the proposed reactions between cations and basic centers.     

Calorimetric comparison of the interactions between salivary proteins and Streptococcus mutans with and without antigen I/II

Antigen I/II can be found on streptococcal cell surfaces and is involved in their interaction with salivary proteins. In this paper, we determine the adsorption enthalpies of salivary proteins to Streptococcus mutans LT11 and S. mutans IB03987 with and without antigen I/II, respectively, using isothermal titration calorimetry. In addition, protein adsorption to the cell surfaces was determined spectrophotometrically. S. mutans LT11 with antigen I/II, yielded a much higher, exothermic adsorption enthalpy at pH 6.8 (ranging from −2073 × 10⁻⁹ to −31707 × 10⁻⁹ μJ per bacterium) when mixed with saliva than did S. mutans IB03987 (−165 × 10⁻⁹ to −1107 × 10⁻⁹ μJ per bacterium) at all bacterial concentrations studied (5 × 10⁹, 5 × 10⁸, and 5 × 10⁷ ml⁻¹), largest effects per bacterium being observed for the lowest concentration. However, the enthalpy of salivary protein adsorption to S. mutans LT11 became smaller at pH 5.8. Adsorption isotherms for the S. mutans LT11 showed considerable protein adsorption at pH 6.8 (1.2–2.1 mg/m²), that decreased only slightly at pH 5.8 (1.1–1.6 mg/m²), with the largest amount adsorbed at the lowest bacterial concentration. This suggests that the protein(s) in the saliva with the strongest affinity for antigen I/II is (are) readily depleted from saliva. In conclusion, antigen I/II surface proteins on S. mutans play a determinant role in adsorption of salivary proteins through the creation of enthalpically favorable adsorption sites.     

Amberlite XAD-2 functionalized with o-aminophenol: synthesis and applications as extractant for copper(II), cobalt(II), cadmium(II), nickel(II), zinc(II) and lead(II)

A stable chelating resin matrix was synthesized by covalently linking o-aminophenol (o-AP) with the benzene ring of the polystyrene–divinylbenzene resin, Amberlite XAD-2, through a –N=N– group. Elemental analyses, thermogravimetric analysis (TGA) and infrared spectra have characterized the resulting chelating resin. It has been used to preconcentrate Cu²⁺, Cd²⁺, Co²⁺, Ni²⁺, Zn²⁺ and Pb²⁺, prior to their determination by flame atomic absorption spectrometry. The optimum pH values for quantitative sorption of Cu, Cd, Co, Ni, Zn and Pb are 6.2–7.4, 5.6–7.2, 5.6–9.0, 6.0–9.0, 5.7–7.0 and 5.0–6.0, respectively. These metals are desorbed (recovery 91–98%) with 4 mol dm⁻³ HNO₃. The sorption capacity of the resin is 3.37, 3.42, 3.29, 3.24, 2.94 and 3.32 mg of metal g⁻¹ of resin, respectively, for Cu, Cd, Co, Ni, Zn and Pb. The effect of NaF, NaCl, NaNO₃, Na₂SO₄, and Na₃PO₄ on the sorption of these metal ions has been investigated. These electrolytes are tolerable up to 0.01 mol dm⁻³ in case of all the metal ions, except Cl⁻ which is tolerable even up to 0.1 mol dm⁻³ for Zn and 1.0 mol dm⁻³ for Pb. The preconcentration factor for Cu, Cd, Co, Ni, Zn and Pb are 50, 50, 100, 65, 40 and 40 (concentration level 10–25 μg dm⁻³) respectively. Simultaneous enrichment of the six metals is possible. The method has been applied to determine Cu, Cd, Co, Ni, Zn and Pb content in well water samples (RSD≤8%).     

Silica gel ethyleneimine and its adsorption capacity for divalent Pb, Cd, and Hg

Activated silica gel was directly modified with a cyclic molecule, ethyleneimine, yielding a surface with various nitrogen basic centers, ≡Sil–O(CH₂CH₂NH)_nCH₂CH₂NH₂. Infrared spectroscopy, ¹³C NMR, thermal, and elemental analyses confirmed the covalent attachment of the organic species onto the silica matrix. The purpose of this paper is to describe the interaction involving the grafted species on silica surface with the divalent heavy cations, Pb(II), Cd(II), and Hg(II), from aqueous solutions at room temperature. The process of metal extraction was followed by the batch method and the order of the maximum extraction capacities found was: 1.27 ± 0.04, 1.02 ± 0.02, and 0.98 ± 0.01 mmol g⁻¹ for Pb(II), Cd(II), and Hg(II) chlorides, respectively. These interactions were followed by calorimetric titration. The enthalpies of these processes are: −3.05 ± 0.02, −1.09 ± 0.01, and −9.88 ± 0.03 kJ mol⁻¹ for Pb(II), Cd(II), and Hg(II), respectively. The standard molar Gibbs free energies are in agreement with the spontaneity of the proposed reactions between cation and basic center.     

Biosorption of heavy metals on Aspergillus fumigatus immobilized Diaion HP-2MG resin for their atomic absorption spectrometric determinations

A solid phase extraction procedure based on biosorption of copper(II), lead(II), zinc(II), iron(III), nickel(II) and cobalt(II) ions on Aspergillus fumigatus immobilized Diaion HP-2MG has been investigated. The analytical conditions including amounts of A. fumigatus, eluent type, flow rates of sample and eluent solutions were examined. Good recoveries were obtained to the spiked natural waters. The influences of the concomitant ions on the retentions of the analytes were also examined. The detection limits (3sigma, N = 11) were 0.30 μg l⁻¹ for copper, 0.32 μg l⁻¹ for iron, 0.41 μg l⁻¹ for zinc, 0.52 μg l⁻¹ for lead, 0.59 μg l⁻¹ for nickel and 0.72 μg l⁻¹ for cobalt. The relative standard deviations of the procedure were below 7%. The validation of the presented procedure is performed by the analysis of three standard reference materials (NRCC-SLRS 4 Riverine Water, SRM 1515 Apple leaves and GBW 07605 Tea). The procedure was successfully applied for the determination of analyte ions in natural waters microwave digested samples including street dust, tomato paste, black tea, etc.     

Atomic absorption spectrophotometric determination of trace copper in waters, aluminium foil and tea samples after preconcentration with 1-nitroso-2-naphthol-3,6-disulfonic acid on Ambersorb 572

An atomic absorption spectrophotometric method for the determination of trace copper after adsorption of its 1-nitroso-2-naphthol-3,6-disulfonic acid chelate on Ambersorb 572 has been developed. This chelate is adsorbed on the adsorbent in the pH range 1–8. The copper chelate is eluted with 5 ml of 0.1 mol l⁻¹ potassium cyanide and determined by flame atomic absorption spectrometry (FAAS). The selectivity of the proposed procedure was also evaluated. Results show that iron(III), zinc(II), manganese(II) and cobalt(II) at the 50 μg l⁻¹ level and sodium(I), potassium(I), magnesium(II), calcium(II) and aluminium(III) at the 1000 μg l⁻¹ level did not interfere. A high enrichment factor, 200, was obtained. The detection limit (3σ) of copper was 0.34 μg l⁻¹. The precision of the method, evaluated by seven replicate analyses of solutions containing 5 μg of copper was satisfactory and the relative standard deviation was 1.7%. The adsorption of copper onto Ambersorb 572 can formally be described by a Langmuir equation with a maximum adsorption capacity of 14.3 mg g⁻¹ and a binding constant of 0.00444 l mg⁻¹. The accuracy of the method is confirmed by analysing tomatoes leaves (NIST 1573a) and lead base alloy (NBS 53e). The results demonstrated good agreement with the certified values. This procedure was applied to the determination of copper in waters (tap, river and thermal waters), aluminium foil and tea samples.     

Efficiency and mechanism of new poly(acryl-phenylamidrazone phenylhydrazide) chelating fiber for adsorbing trace Ga, In, Bi, V and Ti from solution

A new po1y(acrylphenylamidrazone phenylhydrazide) chelating fiber is synthesized from polyacrylonitrile fiber and used for preconcentration and separation of trace Ga(III), In(III), Bi(III), V(V) and Ti(IV) from solution (5–50 ng ml⁻¹ Ti(IV) or V(V) and 50–500 ng ml⁻¹ Ga(III), In (III) or Bi(III) in 1000–100 ml of solution can be enriched quantitatively by 0.15 g of fiber at a 4 ml min⁻¹ flow rate in the pH range 5–7 with recoveries >95%). These ions can be desorbed quantitatively with 20 ml of 4 M hydrochloric acid at 2 ml min⁻¹ from the fiber column. When the fiber which had been treated with concentrated hydrochloric acid and washed with distilled water until neutral was reused eight times, the recoveries of the above ions by enrichment were still >95%. Two-hundred-fold to 10 000-fold excesses of Cu(II), Zn(II), Ca(II), Mn(II), Cr(III), Fe(III), Ba(II) and Al(III) caused little interference in the determination of these ions by inductively coupled plasma-atomic emission spectrometers (ICP-AES). The relative standard deviations for enrichment and determination of 50 ng ml⁻¹ Ga, In or Bi and 10 ng ml⁻¹ V or Ti are in the range 1.2–2.7%. The contents of these ions in real solution samples determined by this method were in agreement with the certified values of the samples with average errors <3.7%.     

Specific adsorption of halogen anions on hydrous γ-Al2O3

The paper reports results of a study on the specific adsorption of F⁻, Cl⁻, Br⁻, I⁻, ClO₃⁻, BrO₃⁻, IO₃⁻ and IO₄⁻ on hydrous γ-Al₂O₃. The isotherms of the anion adsorption and the adsorption dependencies on pH and the ionic strength of the solution have been determined under the equilibrium conditions. According to the degree of affinity to γ-Al₂O₃, the anions can be ordered as: I⁻3⁻−−3⁻3⁻4⁻−. It has been established that the sorption of IO₄⁻ and F⁻ involves the formation of surface complexes in the inner co-ordination sphere, whereas that of Cl⁻, Br⁻, I⁻, ClO₃⁻, BrO₃⁻ and IO₃⁻ takes place through formation of ion pair complexes in the outer co-ordination sphere. In the dynamic system, the exchange isoplanes and elution curves have been determined for selected anions on columns filled with Al₂O₃. It has been shown that γ-Al₂O₃ can be used for isolation and concentration of IO₃⁻ from natural waters in order to decrease the limit of the ions determination to 2 μg l⁻¹. Using differential pulse voltammetry (DPV), after isolation and concentration on γ-Al₂O₃, the content of iodates has been determined in mineral, marine and tap water doped with these ions.     

Facilitated Cd(II) transport across CTA polymer inclusion membrane using anion (Aliquat 336) and cation (D2EHPA) metal carriers

PIMs have been involved as affinity membranes for recovery of metals (Cd, Pb, Zn) by facilitated transport from aqueous solutions under different speciation forms, either anionic or cationic. The motivation of this work is to compare the efficiency of the recovery process in the case of Cd(II) using extractants such as D2EHPA and Aliquat 336 that can form complexes with the cation Cd²⁺ or the anions CdCl₃⁻ and CdCl₄²⁻, respectively. The maximal Cd(II) recovery factors obtained in 8 h are 97.5% and 91.8% with D2EHPA and Aliquat 336, respectively. Although the transport fluxes with both carriers are not strongly different (ca. 2 μmol m⁻² s⁻¹), the recovery process in case of mixture of metals is better achieved with Aliquat 336. PIMs have shown a very good stability and a constancy of the transmembrane transport flux over 12 replicate measurements, each one lasting for 8 h repeated every 24 h.     

Application of a new resin functionalised with 6-mercaptopurine for mercury and silver determination in environmental samples by atomic absorption spectrometry

Polystyrene–divinylbenzene (8%) has been functionalised by coupling it through an ---N=N--- group with 6-mercaptopurine. The resulting chelating resin has been characterised by using elemental analysis, thermogravimetric analysis and infrared spectra. The resin is highly selective for Hg(II) and Ag(I) and has been used for preconcentrating Hg(II) and Ag(I) prior to their determination by atomic absorption spectrometry. The maximum sorption capacity for Hg(II) and Ag(I) was found to be 1.74 and 0.52 mmol g⁻¹, respectively, over the pH range 5.5–6.0. The calibration range for Hg(II) was linear up to 10 ng ml⁻¹ with a 3σ detection limit of 0.02 ng ml⁻¹; the calibration range for Ag(I) was linear up to 5 μg ml⁻¹ with a detection limit of 29 ng ml⁻¹. The recoveries of the metals were found to be 99.7±3.8 and 101.3±4.1% at the 95% confidence level for both Hg(II) and Ag(I). In column operation, it has been observed that Hg(II) and Ag(I) in trace quantities can be selectively separated from geological, medicinal and environmental samples.     

Electrochemiluminescence sensor using tris(2,2′-bipyridyl)ruthenium(II) immobilized in Eastman-AQ55D–silica composite thin-films

An electrochemiluminescence (ECL) sensor with good long-term stability and fast response time has been developed. The sensor was based on the immobilization of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) into the Eastman-AQ55D–silica composite thin films on a glassy carbon electrode. The ECL and electrochemistry of Ru(bpy)₃²⁺ immobilized in the composite thin films have been investigated, and the modified electrode was used for the ECL detection of oxalate, tripropylamine (TPA) and chlorpromazine (CPZ) in a flow injection analysis system and showed high sensitivity. Because of the strong electrostatic interaction and low hydrophobicity of Eastman-AQ55D, the sensor showed no loss of response over 2 months of dry storage. In use, the electrode showed only a 5% decrease in response over 100 potential cycles. The detection limit was 1 μmol l⁻¹ for oxalate and 0.1 μmol l⁻¹ for both TPA and CPZ (S/N=3), respectively. The linear range extended from 50 μmol l⁻¹ to 5 mmol l⁻¹ for oxalate, from 20 μmol l⁻¹ to 1 mmol l⁻¹ for TPA, and from 1 μmol l⁻¹ to 200 μmol l⁻¹ for CPZ.     

Preliminary results on the determination of ultratrace amounts of cadmium in tea samples using a flow injection on-line solid phase extraction separation and preconcentration technique to couple with a sequential injection hydride generation atomic fluorescence spectrometry

In this work, a method was developed for determination of ultra-trace levels of Cd in tea samples by atomic fluorescence spectrometry (AFS). A flow injection solid phase extraction (FI-SPE) separation and preconcentration technique, to on-line couple with a sequential injection hydride generation (SI-HG) technique is employed in this study. Cd was preconcentrated on the SPE column, which was made from a neutral extractant named Cyanex 923, while other matrix ions or interfering ions were completely or mostly separated off. Conditions for the SPE separation and preconcentration, as well as conditions for the HG technique, were studied. Due to the separation of interfering elements, Cd hydride generation efficiency could be greatly enhanced with the sole presence of Co²⁺ with a concentration of 200 μg L⁻¹, which is much lower than those in other works previously reported. Interferences on both the Cd separation and preconcentration, and Cd hydride generation (HG) were investigated; it showed that both the separation and preconcentration system, and the HG system had a strong anti-interference ability. The SPE column could be repeatedly used at least 400 times, a R.S.D. of 0.97% was obtained for 6 measurements of Cd with 0.2 μg L⁻¹ and a correlation coefficiency of 1.0000 was obtained for the measurement of a series of solutions with Cd concentrations from 0.1 to 2 μg L⁻¹. The method has a low detection limit of 10.8 ng L⁻¹ for a 25 mL solution and was successfully validated by using two tea standard reference materials (GBW08513 and GBW07605).     

Determination of trace amounts of vanadium by UV-vis spectrophotometric after separation and preconcentration with modified natural clinoptilolite as a new sorbent

Natural clinoptilolite was used as a sorbent material for solid phase extraction and preconcentration of vanadium. The clinoptilolite was first saturated with a cation such as nickel(II) and then modified with benzyldimethyltetradecyleammonium chloride (BDTA) for increasing sorption of 4-(2-pyridylazo)resorcinol (PAR). Vanadium–PAR complex was quantitatively retained on the sorbent by the column method at the pH range 6.2–7.0 at a flow rate of 1 mL min⁻¹. It was removed from the column with 5.0 mL of dimethylformamide solution at a flow rate of 0.8 mL min⁻¹ and determined by UV–vis spectrophotometry at λ_max = 550 nm. 0.031 μg of vanadium can be concentrated from 450 mL of aqueous sample (where detection limit as 0.07 ng mL⁻¹ with preconcentration factor of 90). Relative standard deviation for eight replicate determination of 5.0 μg of vanadium in final solution is 2.1%. The interference of number of anions and cations has been studied in detail to optimize the conditions and method was successfully applied for determination of all vanadium as V(IV) form in standard samples.